BATTERY CELL HOUSING AND METHOD FOR MANUFACTURING

Description

[0001] The invention relates to a battery cell housing and a method for manufacturing a battery cell housing.

[0002] Battery cell housings are manufactured in a wide variety of shapes. Besides pouch and cylindrical battery cell housings, prismatic battery cell housings are also frequently used. Prismatic battery cell housings consist of a casing with a generally rectangular cross-section, thus enabling a simple and space-saving arrangement of battery cells. Prismatic battery cell housings have a base and a lid with means for contacting the two electrical terminals of the battery cell.

[0003] Currently, prismatic battery cell housings in the form of prismatic cups are predominantly manufactured from a sheet blank cut from an aluminum alloy strip using combined deep-drawing and drawing processes with numerous drawing stages. Due to the large number of drawing stages in the manufacturing process, only aluminum alloys with particularly good deep-drawing properties can be used for producing the housing. This large number of drawing stages increases the cost of the process.

[0004] Alternatively, extrusion can be used. Extrusion works best with soft aluminum alloys. Higher-strength aluminum alloys result in increased pressing forces and reduce productivity. Soft aluminum alloys have the disadvantage of being less suitable for meeting the strength requirements of the battery cell casing while maintaining a low weight.

[0005] US patent application US 2022 / 0102787 A1 discloses a battery cell casing which achieves a battery cell volume of more than 50% by providing elongated, rectangular, individual battery cells. How the individual, prismatic battery cell casings are manufactured is not disclosed.

[0006] Document CN113385943A discloses a plant and a method for manufacturing a battery housing comprising a rectangular tube made of aluminium.

[0007] Starting from this premise, the object of the present invention is to provide a battery cell housing that can be manufactured very simply and simultaneously allows the use of a wide range of aluminum alloys and housing dimensions in order to flexibly respond to different requirements of the battery cell housing, such as increased strength requirements, thermal conductivity requirements, or installation space requirements. Furthermore, the invention aims to propose a method for manufacturing the battery cell housing according to the invention.

[0008] The above-mentioned problem is solved by a battery cell housing according to claim 1 and a method for its manufacture according to claim 11.

[0009] According to the invention, the battery cell housing has a roll-formed tube body made of an aluminum alloy as the battery cell housing shell, wherein the battery cell housing shell is joined in the longitudinal direction, preferably by form-fitting, friction-fitting and / or material-fitting, and has at least a rectangular cross-section in some areas, wherein the battery cell housing shell is roll-formed from an aluminum alloy strip.

[0010] The longitudinal direction of the battery cell casing is defined here as the axis of the tube body, which is perpendicular to the tube cross-section. By providing the battery cell casing from roll-formed tube bodies joined longitudinally by form-fit, friction-fit, and / or material-fit seams, it can be manufactured very precisely and in high volumes from a wide variety of aluminum alloys. The height and width of the battery cell casing are adjustable very precisely and flexibly through the roll-forming process. The length of the battery cell casing, i.e., its longitudinal extent, can also be varied by cutting the roll-formed tube body to length, allowing for very precise geometries of the battery cell casing.

[0011] The tube body can optionally be painted after the longitudinal seam joining process (form-fit, friction-fit, and / or material-fit) to provide a battery cell casing with a painted surface. Roll forming of painted aluminum strips is also possible to produce a painted battery cell casing. This offers the advantage that the battery cell casing can be electrically insulated from the electrode winding or stack, and the corrosion protection of the casing is also improved.

[0012] Suitable joining methods for the form-fit, friction-fit, and / or material-fit connection in the longitudinal direction include welding processes such as metal inert gas welding (MIG welding), friction stir welding, laser welding, or induction welding, as well as soldering, bonding, and flanging. According to a preferred embodiment, the battery cell casing is longitudinally welded and has a weld seam running lengthwise. Longitudinal seam welding of tube bodies is a technology known from tube manufacturing that can achieve high welding speeds and a high-quality weld seam on the battery cell casing. Longitudinal seam welding can be performed inline with the manufacturing of the battery cell casing, for example, after roll forming and before cutting the battery cell casing to length.

[0013] To meet the desired strength requirements of the battery cell housing, depending on the chosen aluminum alloy, the wall thickness of the battery cell housing shell is preferably 0.2 mm to 1.2 mm, according to a further embodiment. Higher strength aluminum alloys allow for thinner walls with larger internal volumes. This, in turn, allows for optimization of the volumetric energy density of the battery cell, as a larger volume fraction of the battery cell is available for active material.

[0014] In a further embodiment of the prismatic battery cell housing, the ratio of height to width of the battery cell housing shell is greater than 3 and less than 10, preferably 5 to 8. The height to width ratio of the battery cell housing shell can be easily provided by a roll forming process.

[0015] According to a further embodiment of the prismatic battery cell housing, if the inner radii R i of the battery cell housing shell meet the following condition with respect to the thickness d of the aluminum alloy strip: R i ≤ 2.5 *d, preferably R i ≤ 1.5 *d or particularly preferably 0.1 *d ≤ R i ≤ 1.5 *d, then, on the one hand, good stability of the battery cell housing can be achieved and, on the other hand, an optimized internal volume of the battery cell housing can be provided, since sufficient space is available for a trouble-free arrangement of an electrode winding or electrode stack of the battery cell.

[0016] In a further embodiment of the battery cell housing, the housing shell comprises at least one pressure relief device, preferably at least one bursting element and / or pressure relief valve, which protects the battery cell housing from exceeding a critical pressure inside the housing. The at least one pressure relief device can be introduced or arranged in or on the battery cell housing shell before, during, or after the roll forming process, for example, by laser cutting, embossing, punching, friction-fit, and / or material-fit insertion. The pressure relief device can be triggered when the pressure inside the battery cell housing rises to, for example, more than 5 bar, preferably more than 7.5 bar, in order to prevent a further pressure increase and / or to reduce the pressure in order to avoid critical thermal runaway in the battery cell.

[0017] Preferably, a joint, in particular a weld, is arranged on the long-narrow surface of the battery cell casing. The long-narrow surface refers to the side of the battery cell casing that has the smaller width perpendicular to the roll forming direction, i.e., the longitudinal direction of the battery cell casing. This results in good joinability, or weldability, of the roll-formed tube body in the longitudinal direction, combined with comparatively low mechanical stress during pressure increases during battery operation or in the event of damage. At the same time, the long-narrow surface allows for greater dimensional tolerances with regard to the joint or weld design without adversely affecting the electrode winding or electrode stack.

[0018] The weldability of roll-formed aluminum alloy strip, particularly during MIG or induction welding, is improved by ensuring that the surface tension of the strip is greater than 30 mN / m, preferably greater than 40 mN / m, and most preferably greater than 50 mN / m, preferably immediately before welding. The surface tension of the roll-formed aluminum strip can be measured with good accuracy, for example, using test inks. For this purpose, the aluminum alloy strip is subjected to degreasing or corona treatment using a plasma. This can be carried out, for example, inline with the production of the welded housing cell shell.

[0019] According to the invention, the battery cell casing consists of an aluminum alloy with the following composition in wt.%: Si < 0,5 % , Fe < 0 , 8 % , Cu < 0 , 5 % , Mn ≤ 1 , 5 % , Mg < 1 , 3 % , preferably < 0.5% or 2.5% < Mg < 6.0%, preferably 3.0% < Mg < 6.0% Cr < 0 , 2 % , Zn < 0 , 25 % , Ti ≤ 0 , 1 % , preferably 0.001% ≤ Ti ≤ 0.1%

[0020] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%.

[0021] Aluminum alloys with the aforementioned composition are generally well roll-formed and are also weldable. Furthermore, depending on factors such as the copper, manganese, or magnesium content, they can provide varying levels of strength for the battery cell casing. Si contents of less than 0.5 wt.% enable a low tendency for hot cracking during welding of the battery cell casing. Fe contents of less than 0.8 wt.% also allow for a high recycled content and further bind Si in conjunction with Mn and Al in AlMnFeSi phases, which further reduces the tendency for hot cracking during welding. Cu contents of less than 0.5 wt.% allow the utilization of copper's strength-enhancing effect without significantly impairing corrosion resistance. Moreover, higher Cu contents would increase the tendency for hot cracking. Mn contents of less than 1.5 wt.%, preferably less than 1.2 wt.%, are recommended.-% enables precise control of recrystallization and texture through the formation of dispersoids and, in particular, increases the thermal resistance of the aluminum alloy. Furthermore, Mn, in combination with Fe and Si, forms AlMnFeSi phases, which lower the Si content in the solid solution and thus reduce the tendency to hot crack. Mg contents of less than 1.0 wt.%, preferably less than 0.5 wt.%, result in a moderate increase in strength with low hot cracking tendency during welding. Cr contents of less than 0.2 wt.% are suitable for the formation of further dispersoid phases, which in turn stabilize the microstructure under thermal stress. Zn contents of less than 0.25 wt.% and Ti contents of a maximum of 0.1 wt.% or from 0.001 wt.% to a maximum of 0.1 wt.%, respectively, enable the use of recycled alloys, especially Mn-containing recycled alloys. In addition, a Ti content of 0.001 wt.% to 0.1 wt.% allows for...-% the addition of titanium-based grain refiners to optimize the cast microstructure. By limiting the unavoidable impurities to a maximum of 0.05 wt% individually and a maximum of 0.15 wt% in total, the positive effects of the alloying elements are not altered.

[0022] Alternatively, a Mg content of more than 2.5 wt.% and less than 6.0 wt.%, preferably more than 3.0 wt.% and less than 6.0 wt.%, can be provided in order to ensure the highest possible strength of the battery cell casing with minimal wall thickness and thus optimized weight of the prismatic battery cell, as well as low hot cracking tendency during welding and therefore high process reliability.

[0023] If strength and weight are not the primary concerns for the battery cell casing, but rather the best possible thermal conductivity, then it is advantageous if the battery cell casing is made of an aluminum alloy of type AA1xxx with the following composition in wt.%: Si < 0 , 25 % , Fe < 0 , 4 % , Cu < 0 , 2 % , Mn ≤ 0 , 05 % , Mg < 0 , 5 % , Cr < 0 , 2 % , Zn < 0 , 1 % , 0 , 001 % ≤ Ti ≤ 0 , 1 % ,

[0024] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%.

[0025] AA1xxx aluminum alloys, for example type AA1050, are very weldable because the proportion of alloying elements that increase hot cracking susceptibility (Si, Cu, Mg) is significantly reduced. Furthermore, these alloys exhibit high corrosion resistance. In the mill-hardened condition H18, they also provide sufficiently high strength combined with very high thermal conductivity. High thermal conductivity of the battery cell casing ensures rapid heat dissipation from the interior of the battery cell, thus improving battery cell performance, especially under high charge or discharge rates. Si contents of less than 0.25 wt.% are preferable to minimize hot cracking susceptibility during welding. Fe contents of less than 0.4 wt.% allow the use of technically pure and industrial primary metals, which is preferable from both availability and cost perspectives. Cu contents of less than 0.2 wt.% are also recommended.-% enables the alloying of copper to increase strength through solid solution formation while simultaneously minimizing hot cracking susceptibility. Manganese, both in solution and in intermetallic phases, has a strongly negative effect on the electrical and thermal conductivity of aluminum alloys and is therefore limited to less than 0.05 wt.%. Magnesium contributes to strength, particularly in work-hardened states, through solid solution hardening. However, hot cracking susceptibility increases with increasing Mg content, so the Mg content is limited to < 0.5 wt.%. Cr, as a dispersoid former, contributes to microstructure control during recovery and recrystallization processes and to stabilizing the microstructure under temperature stress. However, Cr impairs electrical and thermal conductivity, so the Cr content is limited to less than 0.2 wt.%. Zinc impairs corrosion resistance and is therefore limited to less than 0.1 wt.%.-% limited. Ti is used for grain refinement and / or to optimize the cast microstructure during the casting process. However, Ti significantly impairs electrical and thermal conductivity, so the Ti content is limited to 0.001 wt% ≤ Ti ≤ 0.1 wt%.

[0026] According to a further embodiment, the battery cell casing consists of an aluminum alloy of type AA3xxx with the following composition in wt.%: Si < 0 , 6 % , Fe < 0 , 8 % , Cu ≤ 0 , 5 % , 0 , 3 % ≤ Mn ≤ 1 , 5 % , preferably 0.6% ≤ Mn ≤ 1.2% Mg < 1 , 3 % , preferably 0.8% ≤ Mg ≤ 1.3%, further preferably 0.01% < Mg < 0.5% Cr < 0 , 2 % , Zn < 0 , 25 % , Ti ≤ 0 , 1 % , preferably 0.001 wt.% ≤ Ti ≤ 0.1 wt.%,

[0027] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%.

[0028] AA3xxx aluminum alloys, for example of type AA3003, offer higher maximum strengths compared to AA1xxx aluminum alloys, particularly higher maximum yield strength values ​​Rp0.2. A silicon content of less than 0.6 wt.%, in combination with the iron and manganese contents according to the invention in the specified amounts, leads in particular to relatively uniformly distributed, compact particles of the quaternary α-Al(Fe,Mn)Si phase. These precipitated particles increase both the strength of the aluminum alloy and its electrical and thermal conductivity, since they remove iron and manganese from the solid solution without negatively affecting other properties such as corrosion behavior, i.e., electrolyte resistance, or formability. The iron content of less than 0.8 wt.%The -% iron content, in combination with the specified amount of manganese according to the invention, leads to the formation of Al₆(Mn,Fe) phases and, as already explained above, in combination with the specified amounts of silicon and manganese according to the invention, to the precipitation of particles of the quaternary α-Al(Fe,Mn)Si phase. Iron contributes to lowering the solubility of manganese in aluminum, resulting in more manganese being bound in intermetallic phases, which has a positive effect on electrical and thermal conductivity. In addition, the intermetallic phases influence recovery and recrystallization processes and improve the thermal stability of the mechanical properties. Iron contents of more than 0.8 wt.% promote the formation of coarse intermetallic phases, which can impair formability in the deep-drawing process. A copper content of a maximum of 0.5 wt.%By allowing a copper content of -%, the strength of the alloy can be increased through solid solution formation. Furthermore, increased tolerance of the aluminum alloy to copper-containing aluminum alloy scrap is achieved, which facilitates the realization of high recycled material proportions in the production of the battery casing. However, since excessively high copper contents can negatively affect corrosion properties, the copper content is limited to a maximum of 0.5 wt.% according to the invention to achieve sufficiently high electrolyte resistance. The manganese content of 0.3 wt.% ≤ Mn ≤ 1.5 wt.%, preferably 0.6 wt.% ≤ Mn ≤ 1.2 wt.%, leads, as already explained above, in combination with the silicon and iron contents in the specified amounts to the precipitation of particles of the quaternary α-Al(Fe,Mn)Si phase and the Al₆(Mn,Fe) phase.The intermetallic phases impede recovery and recrystallization curtains, thus improving the thermal stability of the mechanical properties. Manganese contents of less than 0.6 wt.% already reduce the strength increase achieved through dispersoid and solid solution hardening. Mn contents below 0.3 wt.% result in an insufficient strength increase through dispersoid and solid solution hardening compared to the 1xxx alloy, while thermal and electrical conductivity deteriorate. Manganese contents of more than 1.5 wt.%, especially more than 1.2 wt.%, promote the formation of coarse intermetallic phases, which adversely affect the forming properties. Furthermore, manganese contents of more than 1.5 wt.%, especially more than 1.2 wt.%, reduce the electrical and thermal conductivity of the battery cell casing so significantly that thermal management becomes inefficient.To achieve improved mechanical properties while maintaining good weldability, the magnesium content in the aforementioned embodiment is limited to less than 1.3 wt.%, preferably 0.8 wt.% ≤ Mg ≤ 1.3 wt.%, and more preferably 0.01% < Mg < 0.5%. The preferred ranges represent compromises between high strength, good formability, and high electrical and thermal conductivity, combined with good weldability and recycling tolerance towards Mg-containing scrap. At higher Mg contents, strength and formability take precedence, albeit with slightly reduced electrical and thermal conductivity. At lower Mg contents, electrical and thermal conductivity take precedence, with reduced strength. Cr, as a dispersoid former, contributes to microstructure control during recovery and recrystallization processes and to stabilizing the microstructure under thermal stress.However, chromium impairs electrical and thermal conductivity, so the chromium content is limited to less than 0.2 wt.%. Zinc impairs corrosion resistance and is therefore limited to less than 0.25 wt.%. Titanium is used for grain refinement and / or to optimize the cast microstructure during the casting process. However, titanium significantly impairs electrical and thermal conductivity, so the titanium content is limited to a maximum of 0.1 wt.%, preferably to 0.001 wt.% ≤ Ti ≤ 0.1 wt.%. AA3xxx aluminum alloys are also highly formable and readily weldable and brazable. The aforementioned upper limits for silicon, iron, copper, magnesium, chromium, zinc, and titanium make the aluminum alloy well-suited for incorporating high recycled content levels of at least 70% to more than 90%.Sufficient strength for the battery cell casing is already achieved for aluminum alloys of type AA3003 in the H14 or H16 state. Higher-strength AA3xxx aluminum alloys, such as AA3104, also achieve these properties in the H14 state.

[0029] To provide even higher strengths, according to a further embodiment the battery cell casing is made of an aluminum alloy of type AA5xxx with the following composition in wt.%: Si < 0 , 3 % , Fe < 0 , 4 % , Cu < 0 , 2 % , Mn < 0 , 8 % , 2 , 5 % < Mg < 6 , 0 % , preferably 3.0% < Mg < 6.0% Cr < 0 , 2 % , Zn < 0 , 25 % , Ti ≤ 0 , 1 % , preferably 0.001% ≤ Ti ≤ 0.1%

[0030] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%.

[0031] Battery cell casings made of AA5xxx alloys can meet demanding load requirements due to their high achievable strengths and can therefore be used, for example, as structural components in vehicles. The increase in strength is due to a magnesium content of more than 2.5 wt.%, preferably more than 3.0 wt.%. At these magnesium contents, the maximum susceptibility to hot cracking is already exceeded, so that magnesium contents of more than 2.5 wt.%, preferably more than 3.0 wt.%, enable an efficient welding process. At least 6.0 wt.%, processing the aluminum alloy by cold rolling becomes increasingly difficult, as work hardening during cold rolling increases significantly and the susceptibility to intergranular corrosion also increases considerably. Silicon contents of less than 0.3 wt.% are not suitable.Fe content is preferable to minimize the tendency for hot cracking during the welding process and to prevent the formation of Mg₂Si phases, which deplete the solid solution of Mg and thus reduce its hardening. Fe is present as an impurity in primary industrial metals and through recycling. Fe contents of less than 0.4 wt.%, in combination with Mn contents of less than 0.8 wt.%, lead to the formation of AlMnFe phases, which, as dispersoids, contribute to the efficient control of recrystallization and recovery, thus allowing for optimization of the grain structure. Higher Fe contents can lead to the formation of coarse intermetallic phases, while Mn contents above 0.8 wt.% undesirably reduce both thermal and electrical conductivity. Cr, as a dispersoid former, contributes to controlling the microstructure during recovery and recrystallization processes and to stabilizing the microstructure under thermal stress.However, chromium impairs electrical and thermal conductivity, so the chromium content is limited to less than 0.2 wt.%. Zinc impairs corrosion resistance and is therefore limited to less than 0.25 wt.%. Titanium is used for grain refinement and / or to optimize the cast microstructure during the casting process. However, titanium reduces electrical and thermal conductivity comparatively significantly, so the titanium content is limited to a maximum of 0.1 wt.%, preferably 0.001 wt.% ≤ Ti ≤ 0.1 wt.%.

[0032] For battery cell casings to achieve sufficient pressure stability, a sufficiently high strength of the casing is required. For example, casings made of roll-formed aluminum alloy strips consisting of alloy type AA 5754 already achieve sufficient strength in the H12 condition. If aluminum alloy strips consisting of aluminum alloy type AA 5083 are used to manufacture the casing, they achieve sufficient strength even in the soft-annealed O condition.

[0033] The aluminum alloy strip according to the invention, from which the battery cell casing shell of the battery cell housing is roll-formed, has a yield strength Rp0.2 of at least 120 MPa, preferably at least 150 MPa. This ensures that the battery cell housing achieves sufficient pressure stability, particularly with regard to the strength of the battery cell casing shell, without requiring an excessively large wall thickness, which would significantly reduce the volumetric energy density of the battery cell.

[0034] Finally, according to the invention, the battery cell housing has two covers that are connected to the battery cell housing shell by a form-fit, friction-fit, and / or material-fit connection. The covers can be made of a wide variety of materials. Plastics are suitable, as are ceramic materials or stamped aluminum alloy sheets. The covers can be glued, welded, or soldered to form a material-fit connection. For covers made of aluminum alloys, laser welding or laser soldering is a suitable option. However, crimping to create a form-fit and / or friction-fit connection is also possible with aluminum materials.

[0035] The problem outlined above is also solved by a method for manufacturing a battery cell housing according to the invention in that an aluminium alloy strip is produced from a bar or a casting strip by hot and / or cold rolling, the rolled aluminium alloy strip is further processed into a closed tube with a cross-section that is at least partially rectangular by means of roll forming and longitudinal seam joining by form, friction and / or material joining, in particular longitudinal seam welding, and the roll-formed and joined tube is cut perpendicular to its longitudinal axis into shorter sections which are used as battery cell casing shells.

[0036] The inventive method allows battery cell housings with at least partially rectangular cross-sections to be manufactured in a simple and economical manner, whereby fundamentally different aluminum alloys can be used to meet various requirements for the battery cell housings.

[0037] The welding speed for longitudinal seam welding can preferably be more than 2.5 m / min, more than 5 m / min, or preferably more than 10 m / min. By using different aluminum alloys, for example, high-thermal-conductivity aluminum alloys of type AA1xxx, recyclable aluminum alloys of type AA3xxx, up to high-strength aluminum alloys of type AA5xxx, battery cell housings with a battery cell housing shell having a cross-section that is at least partially rectangular, can be produced using the same process.

[0038] Preferably, according to a first embodiment of the method, a post-processing of the weld root is carried out to smooth it. This further reduces the influence of the weld root on the electrode winding or electrode stack of the battery cell. This process step can be performed immediately after welding, particularly longitudinal seam welding. Weld root smoothing can be achieved, for example, by reheating the weld with a welding jet in the conduction mode.

[0039] According to a further embodiment of the method, after cutting the battery cell casing to the required length, one of the two previously open end faces of the battery cell casing is closed with a lid in a form-fitting, friction-fit and / or material-fit manner in order to provide a battery cell casing in the form of a cup with at least partially rectangular cross-section for receiving the electrode winding or electrode stack.

[0040] In further automated steps, an electrode coil or stack can be inserted into this cup, which is closed on one side, and the cell can then be filled with electrolyte. Finally, the cell casing can be sealed with a second lid using a form-fit, friction-fit, and / or material-fit connection to create a finished prismatic battery.

[0041] Alternatively, the electrode winding or stack can first be inserted into the battery cell casing, ensuring particularly good accessibility to the joining zones for connecting the electrode stacks to the terminals. The battery cell casing can then be sealed on one side with a lid, either by positive locking, friction, and / or material locking, creating a cup that can be filled with electrolyte in the subsequent manufacturing process and then sealed with a second lid, again by positive locking, friction, and / or material locking. Alternatively, filling with electrolyte after the battery cell casing has been sealed on both sides with the lid, either by positive locking, friction, and / or material locking, is also conceivable.

[0042] The invention will be explained in more detail below with reference to exemplary embodiments in conjunction with the drawing. The drawing shows Fig. 1 shows a schematic representation of an embodiment of a battery cell housing casing of a prismatic battery cell housing; Fig. 2 and Fig. 3 show a schematic top view of two covers for the prismatic battery cell housing made of... Fig. 1 and Fig. 4 in a schematic view an embodiment of a method according to the invention for manufacturing a battery cell housing.

[0043] Fig. 1 Figure 1 shows an embodiment of a battery cell housing shell 1, which comprises a welded, roll-formed tubular body with a cross-section that is at least partially rectangular. The battery cell housing shell 1 is roll-formed from an aluminum alloy strip 2. The battery cell housing shell 1 of the embodiment is longitudinally joined by form-fit, friction-fit, and / or material-fit connection; in this case, longitudinally welded. The weld seam 3 of the battery cell housing shell 1 is located on the long-narrow side 5 of the battery cell housing shell in this embodiment.

[0044] Preferably, the wall thickness of the battery cell casing is 0.2 mm to 1.2 mm. The wall thickness, in combination with the selection of an aluminum alloy, allows for specific properties of the battery cell casing 1 with at least a partially rectangular cross-section, thus enabling the corresponding battery cell casing to be provided.

[0045] According to the report, the aluminium alloy of the battery cell casing 1 has the following alloy composition in wt.%: Si < 0 , 5 % , Fe < 0 , 8 % , Cu < 0 , 5 % , Mn ≤ 1 , 5 % , Mg < 1 , 3 % , preferably < 0.5% or 2.5% < Mg < 6.0%, preferably 3.0% < Mg < 6.0% Cr < 0 , 2 % , Zn < 0 , 25 % , 0 , 001 % < Ti < 0 , 1 % ,

[0046] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%.

[0047] Furthermore, the battery cell casing 1 can also consist of an aluminum alloy of type AA1xxx with the following composition in wt.%: Si < 0 , 25 % , Fe < 0 , 4 % , Cu < 0 , 2 % , Mn ≤ 0 , 05 % , Mg < 0 , 5 % , Cr < 0 , 2 % , Zn < 0 , 1 % , 0 , 001 % < Ti < 0 , 1 % ,

[0048] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%, or from an aluminum alloy of type AA3xxx with the following composition in wt.%: Si < 0 , 6 % , Fe < 0 , 8 % , Cu ≤ 0 , 5 % , 0 , 3 % ≤ Mn ≤ 1 , 5 % , preferably 0.6% ≤ Mn ≤ 1.2% Mg < 1 , 3 % , preferably 0.8% ≤ Mg ≤ 1.3%, further preferably 0.01% < Mg < 0.5%. Cr < 0 , 2 % , Zn < 0 , 25 % , 0 , 001 % < Ti < 0 , 1 % ,

[0049] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%, or an aluminum alloy of type AA5xxx with the following composition in wt.%: Si < 0 , 3 % , Fe < 0 , 4 % , Cu < 0 , 2 % , Mn < 0 , 8 % , 2 , 5 % < Mg < 6 , 0 % , preferably 3.0% < Mg < 6.0% Cr < 0 , 2 % , Zn < 0 , 25 % , 0 , 001 % < Ti < 0 , 1 % ,

[0050] Residual Al and unavoidable impurities, individually a maximum of 0.05% and in total a maximum of 0.15%.

[0051] Battery cell casing shells 1 of a battery cell housing can be manufactured from aluminum strips consisting of the aforementioned different aluminum alloys by roll forming. The different compositions of the aluminum alloys result in different property profiles of the battery cell housing, or rather, the battery cell casing shell 1. For example, A1xxx aluminum alloys, in addition to high corrosion resistance, have above all maximum thermal conductivity with preferred yield strength values ​​R p0.2 in the roll-hardened condition H18 or H19. AA3xxx aluminum alloys exhibit high hot strength, very good formability, and good weldability or brazing properties. The recyclable AA3xxx aluminum alloys achieve preferred strengths, especially yield strength values ​​R p0.2, already in the H14 and H16 conditions and can consist of up to more than 90% recycled aluminum.AA5xxx aluminum alloys can provide preferred yield strength values ​​Rp0.2 combined with high ductility even in the O or H12 states. In these microstructures, or even in states with a higher yield strength Rp0.2, AA5xxx aluminum alloys, combined with high ductility, allow for particularly thin wall thicknesses for battery cell casings 1, thus optimizing the volume of the electrode winding or electrode stack of the battery cell.

[0052] The length of the battery cell casing L can, for example, range from 100 mm to 400 mm. Greater lengths L are also conceivable and can be provided without problems using the roll-formed battery cell casing 1.

[0053] According to the in Fig. 1 In the illustrated embodiment, the ratio of height H to width B of the battery cell casing can be greater than 3 and less than 10, preferably 5 to 8. The width B can vary, for example, from 15 to 45 mm, and the height H, for example, from 50 to 200 mm.

[0054] Preferably, the inner radii R i of the battery cell casing 1 with respect to the thickness of each roll-formed aluminium alloy strip 2 are at most 2.5 times, at most 1.5 times or at most 0.1 times up to 1.5 times the sheet thickness d of the aluminium strip 2.

[0055] These inner radii R i lead to a high packing density and thus to an optimization of the volumetric energy density of the battery cells, which can be achieved with the battery cell housings according to the invention, while at the same time enabling a safe production of the battery cell housing shell 1 by roll forming.

[0056] As the exemplary embodiment also shows, the weld seam is preferably arranged on the long-narrow surface 5 of the battery cell housing shell 1, since this position experiences a low load in the event of an increase in internal pressure and is sufficiently accessible for a longitudinal seam welding process.

[0057] On the long-narrow side 5, at least one pressure relief device, shown here as a bursting element 5a, is preferably provided. The bursting element 5a is formed by embossing or laser engraving. The material in the area of ​​the bursting element is thinned by the embossing or locally softened by a laser in such a way as to selectively weaken the battery cell housing at this point, so that above a specific internal pressure, the pressure stability is locally reduced in the area of ​​the bursting element in favor of its surroundings. In the event of an unacceptably high internal pressure of the battery cell housing, it can be selectively relieved of pressure in order to prevent uncontrolled bursting of the entire battery cell housing in the event of a critical thermal runaway and thus to maintain its structural integrity as far as possible.

[0058] The aluminum strip of the battery cell casing 1 has a yield strength Rp0.2 of at least 120 MPa, preferably more than 150 MPa. This ensures that the battery cell casing 1 has very good pressure stability, especially internal pressure stability.

[0059] In Fig. 2 und Fig. 3 The upper cover 6 and the lower cover 9 of a battery cell housing, which has a battery cell casing shell 1, are shown schematically in a top view. An additional embossing line 6a or 9a on the covers 6 and 9 stiffens the cover of the battery cell housing and can be easily incorporated, for example, when using aluminum alloys for manufacturing the covers. For the electrical contacts of the electrode winding of the battery cell, openings are provided in the cover in the Fig. 2 Schematically, two cutouts, 7 and 8, are provided, each intended to accommodate the battery cell terminals. The terminals are marked with a minus and a plus sign. The electrical contacts can be routed through a cover on one side. Alternatively, one electrical contact can be routed through each cover, allowing multiple battery cells to be connected at the respective covers at the tube ends.

[0060] The covers 6 and 9 can be connected to the battery cell casing 1 in different or similar ways by means of form-fitting, friction-fitting and / or material-fitting connections, whereby various joining techniques such as welding, soldering and / or gluing or combinations of several joining techniques are suitable.

[0061] Additionally, the geometry of the covers allows for a purely friction-based connection or a combination of form-fit, friction-fit, and / or material-fit connections. Simultaneously, a purely form-fit connection to the battery cell housing can also be provided, for example, if the cover 6 or 9 is crimped onto a battery cell housing shell. Furthermore, the use of different materials, such as plastics or ceramics, is conceivable for the covers 6 and 9 of the battery cell housing. The connection technology for joining the battery cell housing shell 1 to the covers 6 and 9 therefore depends on the selected cover material.

[0062] Fig. 4 Figure 1 shows a schematic representation of an embodiment of a method for manufacturing a battery cell housing with a battery cell housing shell having at least a partially rectangular cross-section, in which an aluminum alloy strip is produced from an aluminum alloy by hot and / or cold rolling from a bar or a casting strip, the rolled aluminum alloy strip 2 is roll-formed into a tubular battery cell housing shell 1 with at least a partially rectangular cross-section, the battery cell housing shell 1 is welded and cut to length.

[0063] In Fig. 4 Figure 1 schematically shows an aluminum alloy strip 2 wound onto a coil 10. The aluminum alloy strip 2 is unwound from this aluminum coil 10 and fed to a roll forming device 11. In the roll forming device 11, the aluminum alloy strip 2 is then formed as follows: Fig. 4 Figure 1 shows, for example, the process of roll forming a battery cell casing 1 with a rectangular cross-section in various steps 2a, 2b, and 2c. At the end of the roll forming process, a tubular battery cell casing exits the roll forming device 11.

[0064] The tubular battery cell casing 1 with a rectangular cross-section leaves the roll of device 11 and is longitudinally welded via welding means 13. Not shown in Fig. 4 This includes further processing of the weld root, for example, weld smoothing or other post-processing of the weld. Furthermore, before and / or after longitudinal joining or welding of the battery cell casing 1, at least one bursting element can be introduced into the battery cell casing 1 by means of embossing. Battery cell casings 1 of a fixed length L are then cut off using cutting means 14.

[0065] Not shown, for example, is the possibility of painting the battery cell casing 1 before or after welding. Alternatively, the manufactured battery cell casings 1 can also be subjected to individual painting.

[0066] Not shown is in Fig. 4, that after cutting the battery cell casing to the required length, one of the two open ends of the casing can be sealed with a lid in a form-fitting, friction-fit, and / or material-fit manner to provide a battery cell casing in the form of a cup, now open on one side, with a rectangular cross-section at least in some areas, for receiving the electrode winding or electrode stack, followed by filling with an electrolyte. After sealing the other, previously open, side of the cup-shaped battery cell casing, including the provision of the battery cell terminals, a finished battery cell with a casing 1 having a rectangular cross-section at least in some areas is available.

[0067] All previously described manufacturing steps can be carried out in a highly automated manner and enable the economical mass production of battery cell casings 1 in a wide variety of shapes and lengths. This allows battery cell casings with at least a partially rectangular cross-section 1 to be manufactured economically for a wide variety of applications and with a wide variety of properties with regard to the strength or, for example, the thermal conductivity of the battery cell casing.

Claims

1. Battery cell housing, wherein the battery cell housing has a roll-formed tubular body made of an aluminium alloy as the battery cell housing jacket (1), the battery cell housing jacket (1) is joined in the longitudinal direction and has at least in areas a rectangular cross section, the battery cell housing jacket (1) is roll-formed from an aluminium alloy strip (2) and the battery cell housing has two lids (6, 9) connected to the battery cell housing jacket (1) with a form-fit, friction-fit and / or materially, characterised in that the aluminium alloy strip, from which the battery cell housing jacket (1) of the battery cell housing is roll-formed, comprises a yield strength Rp0.2 of at least 120 MPa, preferably at least 150 MPa, wherein the battery cell housing jacket (1) consists of an aluminium alloy having the following composition in wt.%: Si < 0.5 % , Fe < 0.8 % , Cu < 0.5 % , Mn ≤ 1.5 % , Mg < 1.3 % , preferably < 0.5% or 2.5% < Mg < 6.0%, preferably 3.0% < Mg < 6.0%, Cr < 0.2 % , Zn < 0.25 % , Ti ≤ 0.1 % , preferably 0.001% ≤ Ti ≤ 0.1%, the remainder being Al and unavoidable impurities, individually at most 0.05% and in total at most 0.15%..

2. Battery cell housing according to Claim 1, characterised in that the battery cell housing jacket (1) is longitudinally seam-welded and has a weld seam (3) in the longitudinal direction.

3. Battery cell housing according to Claim 1 or 2, characterised in that the wall thickness of the battery cell housing jacket (1) is 0.2 mm to 1.2 mm.

4. Battery cell housing according to one of Claims 1 to 3, characterised in that the ratio of height (H) to width (B) of the battery cell housing jacket (1) is more than 3 and less than 10, preferably 5 to 8.

5. Battery cell housing according to one of Claims 1 to 4, characterised in that the inner radii Ri of the battery cell housing jacket (1) fulfil the following condition with respect to the thickness d of the roll-formed aluminium alloy strip (2): Ri ≤ 2.5*d, preferably Ri ≤ 1.5*d, particularly preferably 0.1 ∗ d ≤ R i ≤ 1.5 ∗ d .

6. Battery cell housing according to one of Claims 1 to 5, characterised in that the battery cell housing jacket (1) has at least one pressure relief means, preferably at least one bursting element (5a) and / or at least one pressure valve, which protects the battery cell housing from exceeding a critical pressure inside the battery cell housing.

7. Battery cell housing according to one of Claims 1 to 6, characterised in that a joining seam, in particular a weld seam (3), is arranged on the long-narrow surface (5) of the battery cell housing jacket (1).

8. Battery cell housing according to Claim 1, characterised in that the battery cell housing jacket (1) consists of an aluminium alloy of the type AA1xxx having the following composition in wt.%: Si < 0.25 % , Fe < 0.4 % , Cu < 0.2 % , Mn ≤ 0.05 % , Mg < 0.5 % , Cr < 0.2 % , Zn < 0.1 % , 0.001 % ≤ Ti ≤ 0.1 % , the remainder being Al and unavoidable impurities, individually at most 0.05% and in total at most 0.15%.

9. Battery cell housing according to Claim 1, characterised in that the battery cell housing jacket (1) consists of an aluminium alloy of the type AA3xxx having the following composition in wt.%: Si < 0.6 % , Fe < 0.8 % , Cu ≤ 0.5 % , 0.3 % ≤ Mn ≤ 1.5 % , preferably 0.6% ≤ Mn ≤ 1.2%, Mg < 1.3 % , preferably 0.8% ≤ Mg ≤ 1.3%, more preferably 0.01% < Mg < 0.5%, Cr < 0.2 % , Zn < 0.25 % , Ti ≤ 0.1 % , preferably 0.001% ≤ Ti ≤ 0.1%, the remainder being Al and unavoidable impurities, individually at most 0.05% and in total at most 0.15%.

10. Battery cell housing according to Claim 1, characterised in that the battery cell housing jacket (1) consists of an aluminium alloy of the type AA5xxx having the following composition in wt.%: Si < 0.3 % , Fe < 0.4 % , Cu < 0.2 % , Mn < 0.8 % , 2.5 % < Mg < 6.0 % , preferably 3.0% < Mg < 6.0%, Cr < 0.2 % , Zn < 0.25 % , Ti ≤ 0.1 % , preferably 0.001% ≤ Ti ≤ 0.1%, the remainder being Al and unavoidable impurities, individually at most 0.05% and in total at most 0.15%.

11. Method for manufacturing a battery cell housing according to Claims 1 to 10, characterised in that - an aluminium alloy strip (2) is manufactured by hot and / or cold rolling from an ingot or a cast strip, - the rolled aluminium alloy strip (2) is further processed by means of roll forming and joining in the longitudinal direction, in particular longitudinal seam welding, to form a closed tubular body made of an aluminium alloy with at least in areas a rectangular cross section, and - the roll-formed tubular body is divided perpendicularly to its longitudinal axis into shorter subsections, which are used as the battery cell housing jacket (1).

12. Method according to claim 11, characterised in that the aluminium alloy strip (2) is longitudinally seam-welded after the roll forming, the welding speed preferably being more than 2.5 m / min, more than 5 m / min or preferably more than 10 m / min.

13. Method according to claim 11 or 12, characterised in that post-processing of the weld seam root is carried out for weld seam root smoothing.

14. Method according to one of claims 11 to 13, characterised in that after cutting the battery cell housing jacket (1) to the required length, one of the two open end faces of the battery cell housing jacket (1) is closed with a form-fit, friction-fit and / or materially by a lid (6a, 9a) in order to provide a battery cell housing in the form of a cup with at least in areas a rectangular cross section for receiving the electrode winding or electrode stack.

15. Method according to one of claims 11 to 14, characterised in that at least one pressure relief means is introduced or arranged in or on the battery cell housing jacket before, during or after the roll forming process by lasering, embossing, punching, friction-fit and / or materially bonded insertion.