Rolled product made of aluminum for a battery cell housing

Abstract

The invention relates to a rolled product made of an aluminum alloy for producing a battery cell housing, to a method for producing the rolled product made of an aluminum alloy, to the use of the rolled product made of an aluminum alloy for producing a battery cell housing, and to a battery cell housing. The problem of proposing a rolled product made of an aluminum alloy that ensures economical use of secondary aluminum and at the same time ensures processability on existing production systems and tools for the manufacturing of battery cell housings is solved in that the rolled product made of an aluminum alloy for producing a battery cell housing has an aluminum alloy having the following alloy constituents in wt.%: 0.1% ≤ Si ≤ 0.7%, 0.2% ≤ Fe ≤ 0.8%, Cu ≤ 0.6%, 0.3% ≤ Mn ≤ 1.5%, 0.025% ≤ Mg ≤ 0.60%, preferably 0.05% < Mg ≤ 0.55%, Cr ≤ 0.25%, Zn ≤ 0.5 %, Ti ≤ 0.2%, the remainder Al and unavoidable impurities, individually at most 0.05%, in total at most 0.15%, wherein the rolled product has a tensile strength Rm of at least 135 MPa to at most 210 MPa, preferably at most 185 MPa, a yield point Rp0.2 of more than 125 MPa to at most 180 MPa, preferably at most 165 MPa, and an elongation A50 of more than 5%, preferably more than 7%.

Description

[0001] Rolled aluminum product for a battery cell housing

[0002] The invention relates to a rolled product made of an aluminum alloy for producing a battery cell housing, a method for producing the rolled product made of an aluminum alloy, the use of the rolled product made of an aluminum alloy for producing a battery cell housing and a battery cell housing.

[0003] A rolled product refers to rolled strips or sheets. Battery cell housings are manufactured from rolled products in a wide variety of shapes. In addition to the pouch design and the cylindrical battery cell housing, a prismatic battery cell housing is also frequently used. Prismatic battery cell housings consist of a battery cell housing shell, which has a substantially rectangular cross-section and thus enables a simple and space-saving arrangement of battery cells.

[0004] Currently, prismatic battery cell housings in the form of prismatic cans are predominantly manufactured from a rolled product made of an aluminum alloy, for example, a rolled product made of an aluminum alloy, using combined deep-drawing and ironing processes with multiple drawing stages. In these processes, the aluminum alloy AA3003 has been used to manufacture the housing as a good deep-drawable aluminum alloy. Often, a large number of drawing stages are required in the manufacturing process.

[0005] Cylindrical battery cell casings are essentially cylindrical in shape. If the height of the cylinder is greater than the diameter, they are called round batteries; otherwise, they are called button cells. Cylindrical battery cell casings are also predominantly manufactured in cup form using deep-drawing and / or ironing processes. Here, too, only the aluminum alloy AA3003 has been used so far.

[0006] Alternative manufacturing processes for prismatic and cylindrical battery cell casings include extrusion, roll forming, and sequential bending or folding. Extrusion uses slugs produced from a rolled product, whereas roll forming creates a tube geometry using successive work rolls or rollers. Sequential bending involves forming a sheet metal blank into a tube geometry in several bending operations (e.g., on presses). Regardless of the process, material-to-material joining processes, particularly laser welding, must be used to seal the battery cell casings. This can include both sealing welding with one or more covers and longitudinal welding of a tube geometry.

[0007] Another variant is the pouch design, in which the battery cell housing is essentially shaped like a pocket or bag. Due to the high demands on strength and mechanical stability, as well as the high demands on electrochemical resistance to the corrosive electrolyte, which also affects the battery cell housing, cylindrical battery cell housings in particular have previously been made of nickel-plated steel.

[0008] As already mentioned, the aluminum alloy AA3003 is typically used for prismatic battery cell casings. For example, US patent application US 2006 / 093908 Al discloses a high-strength battery casing made of a composite material with an outer plastic layer and an aluminum foil made of an aluminum alloy of the type AA8079, 1N30, AA8021, AA3003, AA3004, AA3104, or AA3105.

[0009] The aforementioned aluminum alloys are also known from the Korean patent application KR 2016 0056731 A for deep-drawn battery cell housings for mobile phones, computers and other mobile devices, whereby the Korean patent application also prefers the use of the aluminum alloy type AA3003.

[0010] The Japanese patent application JP 2015 125886 A focuses on the strength and weldability of battery cell casings for battery cell casings containing non-water-based electrolytes and proposes the use of aluminum alloys of type AA3003, AA3203, AA3004, AA3104, AA3005 or AA3105.

[0011] Although various Al-Mn alloys are known from the state of the art for the production of battery cell casings, the aluminum alloy AA3003 has prevailed in battery cell casing production. This is due, on the one hand, to the fact that secondary battery cell casings typically have to protect highly reactive chemicals from environmental influences. On the other hand, the battery cell casing itself must not become the cause of battery cell failures due to contaminants, tiny particles, or chips. This results in very high demands on the processing properties of the rolled product made of an aluminum alloy that meets the requirements of the aluminum alloy AA3003. Accordingly, forming tools used in the production of battery cell casings, for example, are adapted to the specific properties of the aluminum alloy type AA3003 with great complexity and precision.Adapting tools to aluminum alloys with different mechanical properties is cost- and development-intensive and is made difficult by already limited capacities.

[0012] On the other hand, the aluminum alloy AA3003 is only highly recyclable via a closed material cycle. However, closed material cycles are very complex and costly to implement, so the aluminum alloy AA3003 has a high primary aluminum content. Furthermore, battery cells have a long service life of more than 10 years, so recycling the cell casing material can only be achieved after a long period of time. Sustainability requirements, which have increased significantly in recent years, therefore require the production of battery casings with the lowest possible resource use and Ct footprint.

[0013] The most effective way to do this is to reduce the use of energy-intensive primary aluminum by increasing the use of recycled material, also known as secondary aluminum. The latter is obtained by melting aluminum scrap.

[0014] Aluminum scrap is divided into pre-consumer scrap and post-consumer scrap. Pre-consumer scrap is waste that arises during the production of semi-finished or finished products made of aluminum or aluminum alloys in a variety of possible processes. Pre-consumer scrap can be further divided into internal process scrap, which inevitably arises during the manufacturing process of aluminum strips or sheets, such as sprues, offcuts, chips, production residues, or production rejects, and external process scrap, which inevitably arises during further processing into the final product, such as punching grids, chips, or production rejects. Post-consumer scrap is end product whose life cycle has been fully completed and which, after use, becomes waste.It is irrelevant whether the waste was used by an end consumer or not, meaning that it could also have been used in an industrial or commercial facility, for example. Examples of post-consumer scrap include food packaging, especially beverage cans, window frames, lithographic printing plate carriers, cable cores, and automotive components.

[0015] The use of recycled material is therefore hampered by the high safety requirements for processing rolled products made of aluminum alloys into battery cell housings. Based on this, the present invention sets out to propose a rolled product made of an aluminum alloy that ensures the cost-effective use of secondary aluminum while simultaneously ensuring the processability of battery cell housings using existing production equipment and tools.

[0016] According to the present invention, the above-mentioned object is achieved with a rolled product made of an aluminum alloy for producing a

[0017] Battery cell housing is solved by the rolled product comprising an aluminum alloy with the following alloying components in wt.%:

[0018] 0.1% < Si < 0.7%,

[0019] 0.2% < Fe < 0.8%,

[0020] Cu < 0.6%,

[0021] 0.3% < Mn < 1.5%,

[0022] 0.025% < Mg < 0.60%, preferably 0.01% < Mg < 0.60%,

[0023] Cr < 0.25%,

[0024] Zn < 0.5%,

[0025] Ti < 0.2%,

[0026] Remainder Al and unavoidable impurities, individually maximum 0.05%, in total maximum 0.15%, whereby the rolled product has a tensile strength R m of at least 135 MPa up to a maximum of 210 MPa, preferably a maximum of 185 MPa, a yield strength R Po,2 of more than 125 MPa up to a maximum of 180 MPa, preferably a maximum of 165 MPa, and an elongation Aso of more than 5%, preferably more than 7%.

[0027] It has been shown that high recycled content can lead to increased Si contents in the aluminum alloy. However, in combination with high Mg contents, the tendency of the aluminum alloy to hot crack during welding increases significantly. This significantly reduces the process window when using welding processes to manufacture battery cell casings, so that hot cracks can occur after welding. The same applies to the occurrence of weld pores, the formation of which is favored with increasing Mg content due to the low vapor pressure of Mg. The rolled product according to the invention with the above-mentioned composition allows the use of very high recycled content in production.At the same time, the rolled product according to the invention has the mechanical properties of a rolled product of an aluminum alloy of type AA3003 in the H14 temper, which means that the production facilities and tools previously used for rolled products made of an AA3003 alloy can be used for the new material. At the same time, due to the combination of the Si, Fe, Cu, and Mg contents according to the invention, the rolled product is suitable for the production of battery cell housings using high recycling shares in the rolled product. This applies in particular to the use of aluminum packaging scrap and UBC scrap (UBC: used beverage can), i.e. beverage cans made of aluminum alloys, which have significant magnesium and copper contents and are suitable for the production of the aluminum alloy of the rolled product of the battery cell housing.At the same time, a wide process window for welding processes is provided, since the tendency towards hot cracking and the formation of weld pores is reduced by the alloy composition.

[0028] All of the advantages just mentioned are achieved by the alloy composition of the rolled product in combination with the specified mechanical properties for the yield strength R P o.2, the tensile strength R mand the elongation Aso is achieved. Since the aluminum alloy also contains only standard alloying elements, it is itself also easily recyclable, so that the battery cell housing according to the invention can be fed into existing scrap cycles without problems. In addition, the alloy composition results in the electrolyte resistance not being, or not significantly, impaired compared to the already known alloy AA3003, so that economically and sustainably producible battery cell housings can be provided. According to the invention, the silicon content of the aluminum alloy is in the range 0.1 wt.% < Si < 0.7 wt.% and thus allows particularly high recycling rates. In one embodiment of the battery cell housing according to the invention, the silicon content of the aluminum alloy is in the range 0.2 wt.% < Si < 0.60 wt.%, preferably 0.35 wt.% < Si < 0.55 wt.% or more preferably 0.40 wt.% < Si < 0.50 wt.%.The silicon content of 0.1 wt.% < Si < 0.7 wt.%, in combination with the iron and manganese contents according to the invention in the stated amounts, leads in particular to relatively uniformly distributed, compact particles of the quaternary a-Al(e,Mn)Si phase. These precipitated particles increase both the strength of the aluminum alloy and its electrical and thermal conductivity, as they remove iron and manganese from the solid solution, without, however, negatively affecting other properties such as corrosion behavior, i.e. electrolyte resistance, or formability. Silicon contents of less than 0.1 wt.% lead to reduced precipitation of a-Al(Fe,Mn)Si phases, which can lead to impaired electrical and thermal conductivity due to dissolved manganese. In addition, the absence of a-Al(Fe,Mn)Si phases has a negative effect on tool wear. Silicon contents of more than 0.7 wt.-% in combination with magnesium can lead to increased formation of Mg2Si phases, which negatively impacts the solid solution strengthening of the magnesium. The silicon content of the preferred embodiment of 0.2 wt.% < Si < 0.60 wt.%, preferably 0.35 wt.% < Si < 0.55 wt.% and 0.40 wt.% < Si < 0.50 wt.% represents an ideal compromise between high strength and high electrical and thermal conductivity while providing broad process windows for welding.

[0029] According to the invention, the iron content of the aluminum alloy is in the range 0.2 wt.% < Fe < 0.8 wt.%. In one embodiment of the rolled product according to the invention, the iron content of the aluminum alloy is in the range 0.2 wt.% < Fe < 0.65 wt.%, preferably 0.25 wt.% < Fe < 0.55 wt.% The iron content of 0.2 wt.% < Fe < 0.8 wt.% in combination with the manganese content according to the invention in the stated amount leads to the formation of Al6(Mn,Fe) phases and, as already explained above, in combination with the silicon and manganese contents according to the invention in the stated amounts, to the precipitation of particles of the quaternary a-Al(e,Mn)Si phase. Iron contributes to reducing the solubility of manganese in aluminum, whereby more manganese is 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. Iron contents that are too low, less than 0.2 wt.%, on the other hand, severely restrict the tolerance of the aluminum alloy for ferrous scrap, since common scrap grades generally contain a significant iron content. Therefore, excessively restricting the iron content can hinder the realization of high recycling rates. The iron content range of the aforementioned embodiment of 0.2 wt.% < Fe < 0.65 wt.%, preferably 0.25 wt.% < Fe < 0.55 wt.%, therefore represents an ideal combination of recyclability, use of high recycled material content, thermal stability, electrical and thermal conductivity, and formability.

[0030] According to the invention, the copper content of the aluminum alloy is in the range Cu < 0.6 wt.%. In one embodiment of the rolled product according to the invention, the copper content of the aluminum alloy is in the range Cu < 0.3 wt.%, preferably 0.1 wt.% < Cu < 0.2 wt.%, particularly preferably 0.10 wt.% < Cu < 0.20 wt.%. By permitting a copper content of up to 0.6 wt.%, an increased tolerance of the aluminum alloy for copper-containing aluminum alloy scrap is achieved, which favors the realization of high recycled material proportions in the production of battery casings. However, since excessively high copper contents can have a negative effect on the corrosion properties, the copper content is limited according to the invention to a maximum of 0.6 wt.% in order to achieve sufficiently high electrolyte resistance.For improved electrolyte resistance and sufficiently high electrical and thermal conductivity, the copper content in the above-mentioned embodiment is limited to 0.3 wt.%. However, the presence of copper also simultaneously increases the strength of the aluminum alloy through solid solution strengthening, which, however, only becomes significantly apparent at a content of 0.1 wt.%. A preferred range of 0.1 wt.% < Cu < 0.2 wt.% or 0.10 wt.% < Cu < 0.20 wt.% thus represents a compromise between high strength, sufficiently high electrical and thermal conductivity, and further improved electrolyte resistance while maintaining sufficient recycling tolerance.

[0031] According to the invention, the manganese content of the aluminum alloy is in the range 0.3 wt% < Mn < 1.5 wt%. In one embodiment of the rolled product according to the invention, the manganese content of the aluminum alloy is in the range 0.3 wt% < Mn < 1.4 wt%. The manganese content of 0.4 wt.% < Mn < 1.3 wt.% or preferably 0.6 wt.% < Mn < 1.1 wt.%, in combination with the silicon and iron contents in the specified amounts, leads, as already explained above, to the precipitation of particles of the quaternary a-Al(Fe,Mn]Si phase and the Al6(Mn,Fe] phase. The intermetallic phases hinder recovery and recrystallization processes and thus improve the thermal stability of the mechanical properties. Manganese contents of less than 0.3 wt.% result in only a very slight increase in strength through dispersoid and solid solution hardening, so that at least 0.3 wt.% manganese is required. From manganese contents of at least 0.4 wt.-%, significant increases in strength are achieved through dispersoid and solid solution hardening, which are even greater from at least 0.6 wt.% manganese. At manganese contents of more than 1.5 wt.%, the formation of coarse intermetallic phases is favored, which have an adverse effect on the forming properties in the deep drawing process. In addition, manganese contents of more than 1.5 wt.% reduce the electrical and thermal conductivity of the rolled product so much that the thermal management of battery cell housings made from it becomes inefficient. The Mn content is therefore preferably a maximum of 1.5 wt.%, preferably a maximum of 1.3 wt.%, particularly preferably a maximum of 1.1 wt.%. According to a further embodiment, the Mn / Si ratio is preferably more than 0.8, since above this ratio the formation of a-Al(e,Mn)Si phase is favored.

[0032] According to the invention, the magnesium content of the aluminum alloy is in the range 0.0025 wt.% < Mg < 0.60 wt.%, preferably in the range 0.01 wt.% < Mg < 0.60 wt.%. In one embodiment of the rolled product according to the invention, the magnesium content of the aluminum alloy is in the range 0.05 wt.% < Mg < 0.55 wt.%, preferably 0.10 wt.% < Mg < 0.45 wt.% By permitting a magnesium content of up to 0.60 wt.%, a tolerance of the aluminum alloy for magnesium-containing aluminum alloy scrap such as packaging and UBC scrap is achieved, which favors the realization of high recycling rates in the production of battery cell housings with the rolled product according to the invention. At the same time, limiting the Mg content to 0.60 wt.% allows for higher Si contents without the aluminum alloy being prone to hot cracking and weld pore formation when the rolled product is welded.In addition, the presence of magnesium at a content of at least 0.0025 wt.%, preferably at least 0.05 wt.%, particularly preferably more than 0.05 wt.% or more preferably at least 0.10 wt.% leads to solid solution strengthening, which contributes to increased work hardening and thus can provide greater strength. To achieve improved mechanical properties while simultaneously providing optimal process windows for welding processes, the magnesium content is limited to preferred ranges of 0.05 wt.% < Mg < 0.55 wt.%, preferably 0.05 wt.% < Mg < 0.50 wt.% or particularly preferably 0.10 wt.% < Mg < 0.45 wt.% and a compromise is achieved between high strength, good formability and high electrical and thermal conductivity with good recycling tolerance and weldability.

[0033] According to the invention, the chromium content of the aluminum alloy is in the range Cr < 0.25 wt.%. In one embodiment of the rolled product according to the invention, the chromium content of the aluminum alloy is in the range Cr < 0.1 wt.%, preferably Cr < 0.05 wt.%. By permitting a chromium content of up to 0.25 wt.%, the aluminum alloy achieves an increased tolerance for chromium-containing aluminum alloy scrap, which favors the realization of high recycling rates in the production of battery cell housings using the rolled product according to the invention. In addition, chromium also increases strength and forms dispersoids that increase thermal stability and inhibit softening due to recrystallization or recovery. However, since excessive chromium contents can have a negative effect on the electrical conductivity of the aluminum alloy, the chromium content is limited to a maximum of 0.25 wt.% according to the invention.For improved conductivity while still maintaining sufficient recycling tolerance and strength, the chromium content in the above-mentioned embodiment is limited to 0.1 wt.%, preferably 0.05 wt.%.

[0034] According to the invention, the zinc content of the aluminum alloy is in the range Zn < 0.5 wt.%. In one embodiment of the rolled product according to the invention, the zinc content of the aluminum alloy is in the range 0.0050 wt.% < Zn < 0.30 wt.%, preferably 0.02 wt.% < Zn < 0.30 wt.% and more preferably 0.04 wt.% < Zn < 0.25 wt.%. By permitting a zinc content of up to 0.5 wt.%, an increased tolerance of the aluminum alloy for zinc-containing aluminum alloy scrap is achieved, which further promotes the realization of high recycling rates. In addition, zinc also has a strength-enhancing effect. However, since excessively high zinc contents impair the weldability, electrical and thermal conductivity, and corrosion resistance of the aluminum alloy, the zinc content is limited according to the invention to a maximum of 0.5 wt.%. In the mentioned embodiment, the zinc content is within the corridor 0.0050 wt% < Zn < 0.30 wt%, preferably 0.02 wt.-% < Zn < 0.30 wt.%, more preferably 0.04 wt.% < Zn < 0.25 wt.%, whereby an optimal compromise between high strength, good weldability and good electrolyte resistance while still maintaining good recycling tolerance is achieved. The titanium content of the aluminum alloy is in the range Ti < 0.2 wt.% according to the invention. In one embodiment of the rolled product according to the invention, the titanium content of the aluminum alloy is in the range 0.005 wt.% < Ti < 0.1 wt.%, preferably 0.005 wt.% < Ti < 0.05 wt.% By allowing a titanium content of up to 0.2 wt.%, an increased tolerance of the aluminum alloy for titanium-containing aluminum alloy scrap is achieved, which favors the realization of high recycling rates in the production of battery cell housings.However, excessively high titanium contents can negatively impact the forming properties of the aluminum alloy and significantly reduce electrical and thermal conductivity, so the titanium content is limited to a maximum of 0.2 wt.% according to the invention. In contrast, titanium improves grain refinement during casting of the aluminum alloy at a content of 0.005 wt.% and above. To achieve good grain refinement combined with good formability, sufficiently high electrical and thermal conductivity, and sufficient recycling tolerance, the titanium content in the aforementioned embodiment is therefore set within the range 0.005 wt.% < Ti < 0.1 wt.%, preferably 0.005 wt.% < Ti < 0.05 wt.%.

[0035] In addition to the alloying constituents mentioned above, the aluminum alloy of the rolled product according to the invention contains the remainder of aluminum and unavoidable impurities. Unavoidable impurities are alloying constituents that are not intentionally added to the alloy, but are inevitably present in the aluminum alloy due to the manufacturing process. According to the invention, the content of a single unavoidable impurity is limited to 0.05 wt.%, and the total content of all unavoidable impurities is limited to 0.15 wt.%. This ensures that the unavoidable impurities have no, or no significant, negative effects on the properties of the aluminum alloy, for example, through undesirable phase formation.It has been shown that, despite the variations in the chemical composition of the rolled product made from an aluminum alloy with the above-mentioned alloying constituent contents, a combination of mechanical properties of the rolled product can be achieved that meets the high requirements for processing the rolled product into battery cell casings made of the aluminum alloy AA3003, and that the rolled product can be processed on dedicated production lines. This allows battery cell casings with a low carbon footprint to be manufactured sustainably on existing production lines.

[0036] According to a further embodiment, the proportion of recycled metal in the rolled product made of an aluminum alloy is at least 30 wt.%, preferably at least 50 wt.%, particularly preferably at least 70 wt.%, or particularly preferably at least 75% recycled material. Due to the above-described high recycling tolerance of the aluminum alloy of the rolled product, the realization of these high recycling contents for the rolled product according to the invention is possible without negatively affecting the process parameters for preferred manufacturing processes, such as the welding process.

[0037] The associated energy savings enable the production of battery cell housings with the smallest possible carbon footprint and achieve improved sustainability. The recycled material of the rolled product preferably contains at least 30 wt.%, preferably at least 50 wt.%, particularly preferably at least 70 wt.% post-consumer scrap. Since post-consumer scrap only arises at the end of the product life cycle, it is considered particularly sustainable and contributes more to reducing the carbon footprint. Cumulatively or alternatively, the recycled material contains at least 30 wt.%, preferably at least 50 wt.%, particularly preferably at least 70 wt.% or at least 75% pre-consumer scrap, or internal and / or external process scrap. For internal process scrap, the

[0038] The compositions and quantities of the individual alloys are generally very well known, so that the alloy composition resulting from the melting of internal process scrap can be easily determined. External process scrap is less well-defined in its composition than internal process scrap and may require further processing steps. However, it is generated on a large scale, for example, in the production of stamped parts, so that recycling is highly relevant both economically and in terms of sustainability. By recycling external process scrap, the demand for primary metal can be reduced, which reduces the overall carbon footprint. Even if the exemplary embodiments described below have a maximum recycling content of 85%, recycling contents of at least 90% are also achievable with the aluminum alloy composition according to the invention.

[0039] According to a further embodiment of the rolled product, it has the tempering condition H12, H22, H24, H34, or H32. It has been found that even rolled products in the H12 temper meet the mechanical requirements in terms of processability similar to a rolled product made of an AA3003 aluminum alloy. The reannealed tempers H22, H24, H32, and H34 also have the advantage of improved formability.

[0040] If the rolled product made of an aluminum alloy according to a further embodiment of the battery cell housing has a thickness between 0.1 mm and 2.0 mm, the wall thicknesses typical for a battery cell housing can be fully covered. Reducing the thickness to less than 0.1 mm reduces the mechanical stability of the battery cell housing too much. In contrast, with a thickness of more than 2.0 mm, efficient use of material is no longer possible. In addition, the gravimetric and volumetric energy density of the battery cell or of the battery module or battery system would be reduced too much if the rolled product of the battery cell housing had a thickness of more than 2.0 mm. The thickness of the rolled product or sheet is preferably between 0.25 mm and 1.5 mm, in particular between 0.35 mm and 1.2 mm.According to a further embodiment, the rolled product preferably has a degreased surface with surface tensions of more than 30 mN / m, preferably more than 32 mN / m, particularly preferably 34 mN / m, thereby improving the weldability of the rolled product for producing a battery cell housing. The surface tension of the rolled product surface can be achieved, for example, by alkaline or acidic degreasing or pickling and can be measured with good accuracy using test inks.

[0041] According to the invention, the above-mentioned object is also achieved by a method for producing a rolled product from an aluminum alloy with the following method steps:

[0042] - Providing a rolling ingot made of an aluminium alloy with the following composition in wt.%:

[0043] 0.1% < Si < 0.7%,

[0044] 0.2% < Fe < 0.8%,

[0045] Cu < 0.6%,

[0046] 0.3% < Mn < 1.5%,

[0047] 0.025% < Mg < 0.60%, preferably 0.05% < Mg < 0.55%,

[0048] Cr < 0.25%,

[0049] Zn < 0.5%,

[0050] Ti < 0.2%,

[0051] Remainder Al and unavoidable impurities, individually maximum 0.05%, in total maximum 0.15%

[0052] - optional homogenization of the rolling ingot at 480 °C to 625 °C, preferably at 550 °C to 620 °C for at least 0.1 hours, preferably for at least 0.25 hours, preferably for at least 0.5 hours,

[0053] - Hot rolling of the rolling ingot to a hot strip thickness of 2 mm to 10 mm with a hot strip final temperature between 250 °C and 450 °C,

[0054] - cold rolling of the hot strip to final thickness with at least one optional intermediate annealing in the form of soft annealing at 250 °C and 450 °C, wherein the degree of rolling during cold rolling after hot rolling or after the last intermediate annealing to final thickness is less than 25%, preferably less than 22% or particularly preferably less than 18%.

[0055] The aforementioned process steps are preferably carried out in the specified order, whereby the homogenization of the rolling ingot can be carried out separately or integrated into the preheating of the rolling ingot for hot rolling. It has been found that the process just described can be used to produce a rolled product from an aluminum alloy which, when used according to the invention, meets the requirements for a battery cell housing, particularly with regard to strength, electrolyte resistance, and electrical and thermal conductivity with excellent weldability, while simultaneously achieving high recycling rates. Furthermore, this process allows for economical production of the rolled product.

[0056] The rolling ingot from an aluminum alloy is preferably cast using direct cooling continuous casting, also known as direct chill continuous casting or DC continuous casting, which further increases the economic efficiency of the manufacturing process.

[0057] Homogenizing the rolling ingot improves the microstructure of the rolled product, which has a positive effect on strength and formability. The grain structure is refined through homogenization while maintaining an otherwise identical manufacturing process. As a result, the final product has a reduced average grain size after cold rolling, thus improving formability. Homogenization preferably takes place at a temperature of 480°C to 625°C, preferably at 550°C to 620°C, for at least 0.1 hour, preferably for at least 0.25 hours, or preferably for at least 0.5 hours, more preferably for at least 1 hour or 2 hours.

[0058] The preheating temperature at the start of hot rolling is preferably between 390 and 550 °C. The hot rolling of the rolling slab to a hot-rolled strip is carried out such that the final hot strip temperature is between 250 °C and 450 °C, whereby the final hot strip temperature after the last hot rolling pass is preferably between 280 °C and 380 °C, preferably between 310 °C and 360 °C. The hot rolling of the rolling slab can take place either reversibly on a rolling stand or sequentially in a tandem stand. In particular, hot rolling can take place reversibly up to a blank thickness of between 20 mm and 50 mm and the blank can then be rolled to hot strip thickness in a tandem stand. The final hot strip thickness, i.e. the thickness of the finished hot-rolled strip, is 2 mm to 10 mm.In this way, it is ensured that a sufficiently high degree of rolling can be achieved during the subsequent cold rolling, which primarily determines the strength and formability of the rolled product.

[0059] The cold rolling of the rolled product can take place in one or more passes. In one embodiment of the process in which several cold rolling passes are carried out, at least one intermediate annealing step is optionally carried out during cold rolling. In one embodiment of the process, the intermediate annealing takes place in a temperature range between 250°C and 450°C, preferably between 280°C and 400°C, in particular between 300°C and 400°C. The intermediate annealing step is preferably carried out as a recrystallization annealing step, which provides a recrystallized microstructure for the subsequent cold rolling pass. This cold rolling pass can then be carried out with a higher degree of reduction, which has a strength-enhancing effect on the finished rolled product made of an aluminum alloy. All temperature specifications mentioned that characterize annealing processes always refer to peak metal temperatures (PMT), i.e. the highest temperatures of the metal in the annealing furnace.

[0060] According to the invention, the degree of rolling during cold rolling after hot rolling or after the last intermediate annealing is less than 25%, preferably less than 22%, or particularly preferably less than 18% of the final thickness. The low degree of rolling in conjunction with the preceding process steps and the composition of the aluminum alloy of the rolled product ensures that the rolled product achieves the desired strengths with a yield strength of R P o,2 of more than 125 MPa up to a maximum of 180 MPa, a tensile strength R m of at least 135 MPa to a maximum of 185 MPa for processing into battery cells.

[0061] Alternatively, according to a further embodiment, the process can be configured such that, after hot rolling, only cold rolling to final thickness is carried out with at least one optional intermediate annealing in the form of soft annealing at 250°C and 450°C, with a final annealing in a temperature range of 150°C to 280°C to achieve reannealed microstructures in the rolled product at final thickness. In this embodiment, rolling reductions of at least 50% and more are preferably used after the last intermediate annealing to enable a homogeneous and fine-grained microstructure through the final annealing.

[0062] The intermediate annealing takes place at the specified temperature for at least the time necessary to achieve a soft-annealed condition of the cold-rolled strip after the intermediate annealing. This also depends, among other things, on the furnace technology chosen, i.e., whether a continuous furnace or a batch furnace is used.

[0063] The rolled product according to the invention is preferably used for the production of a battery cell housing, wherein the rolled product is preferably produced using a method according to the invention. As already explained above, the use of the rolled product according to the invention for the production of battery cell housings allows a high recycling content to be taken into account in the rolled product without the properties of the battery cell housing or the production resources required for processing having to be changed or renewed. Unlike previously, the use according to the invention leads to highly sustainable battery cell housings with a low CO2 footprint. This result is achieved by using the rolled product according to the invention for battery cell housings of a secondary cell, preferably a lithium-ion secondary cell, a sodium-ion secondary cell, or a solid-state secondary cell.

[0064] According to a further developed use, the battery cell housing has a prismatic design, a cylindrical design, or a pouch design. All three uses benefit from the composition of the aluminum alloy of the rolled product, combined with the mechanical properties, and the possibility of using high recycled content in the aluminum alloy while maintaining the same processing properties.

[0065] If, according to one embodiment of the use, the rolled product is subjected to a plurality of forming steps, preferably involving deep drawing and / or ironing, existing production resources for manufacturing the battery cell housings from a production based on an aluminum alloy AA3003 can also be used for the rolled product according to the invention. This saves significant investment costs.

[0066] Furthermore, the invention relates to a battery cell housing produced from a rolled product according to the invention, wherein the battery cell housing has a prismatic design, a cylindrical design or a pouch design, which can now also be manufactured with a low carbon footprint without a complex material cycle.

[0067] According to a further embodiment of the battery cell housing, the battery cell housing has formed regions obtained by forming, preferably by deep drawing and / or ironing of a rolled product. The corresponding forming processes can be carried out on existing production equipment despite the different material compositions compared to the aluminum alloy AA3003.

[0068] The invention will be explained in more detail below by means of exemplary embodiments in conjunction with the drawing. The drawing shows

[0069] Fig. 1 is a schematic representation of a battery cell of cylindrical design with a battery cell housing according to the invention,

[0070] Fig. 2 is a schematic representation of a battery cell of prismatic design with a battery cell housing according to the invention,

[0071] Fig. 3 is a schematic representation of a battery cell in pouch design with a battery cell housing according to the invention,

[0072] Fig. 4 is a flow chart of a process for producing a rolled product from an aluminum alloy for battery cell casings, and

[0073] Fig. 5 is a flow chart of a process for producing battery cell housings from rolled products made of an aluminum alloy, comprising deep drawing and / or ironing process steps.

[0074] Fig. 1 shows a schematic representation of an embodiment of a battery cell 10 with a cylindrical design. The battery cell 10 has a battery cell housing 11 according to the invention and, next to it, an anode connection 12 and a cathode connection 13. The battery cell housing 11 can, for example, consist of a cylindrical can with a cathode connection 13 and a battery cell housing cover with anode connection 12. Fig. 2 shows a schematic representation of an embodiment of a battery cell 20 with a prismatic design. The battery cell 20 has a battery cell housing 21 according to the invention and, next to it, an anode connection 22 and a cathode connection 23. The prismatic battery cell housing 21 can also, for example, consist of a prismatic can and a battery cell housing cover with the anode and cathode connections 22 and 23.

[0075] Fig. 3 shows a schematic representation of an embodiment of a pouch-type battery cell 30. The battery cell 30 comprises a battery cell housing 31 according to the invention, as well as an anode terminal 32 and a cathode terminal 33.

[0076] Fig. 4 now shows a flow chart of an embodiment of a method according to the invention for producing a rolled product according to the present invention.

[0077] The process comprises, in step A, providing a rolling ingot made of an aluminum alloy. This is typically done using the DC casting process. The aluminum alloy has the following composition in wt.%: 0.1% < Si < 0.7%, 0.2% < Fe < 0.8%, Cu < 0.6%, 0.3% < Mn < 1.5%, 0.025% < Mg < 0.60%, preferably 0.01% < Mg < 0.60%, Cr < 0.25%, Zn < 0.5%, Ti < 0.2%.

[0078] The remainder is Al and unavoidable impurities, each up to 0.05%, and the total up to 0.15%. Preferably, the aluminum alloy can also have the following composition:

[0079] 0.2% < Si < 0.60%, preferably 0.35% < Si < 0.55%,

[0080] 0.2% < Fe < 0.65%, preferably 0.25% < Fe < 0.55%,

[0081] Cu <0.3%, preferably 0.1% <Cu <0.2%,

[0082] 0.3% < Mn < 1.3%, preferably 0.4% < Mn < 1.1%, 0.05% < Mg < 0.50%, preferably 0.1% < Mg < 0.45% Cr < 0.1%, preferably Cr < 0.05%,

[0083] 0.0050% < Zn < 0.30%, preferably 0.02% < Zn < 0.30%, or preferably 0.04% < Zn < 0.25%,

[0084] 0.005% < Ti < 0.1%, preferably 0.005% < Ti < 0.05%,

[0085] Remainder Al and unavoidable impurities, individually maximum 0.05%, in total maximum 0.15%.

[0086] In step B, the rolling ingot thus produced is optionally homogenized for at least 0.1 hours, preferably at least 0.25 hours, or preferably at least 0.5 hours at a temperature of 480 °C to 625 °C, preferably at 550 °C to 620 °C. The homogenization can be integrated into the preheating process of the rolling ingot before hot rolling or can be carried out separately.

[0087] In step C, the rolling ingot is hot-rolled to a final hot-rolled strip thickness of 2 mm to 10 mm with a final hot-rolled strip temperature between 250 °C and 450 °C. In principle, however, the process according to the invention can also include recrystallization annealing after hot rolling, which is not shown in Fig. 4.

[0088] In Fig. 4, cold rolling of the hot strip is performed according to step D following hot rolling. During cold rolling according to step D, at least one optional intermediate annealing step can be performed in the form of soft annealing at temperatures of 250 °C to 450 °C according to step E. After the final intermediate annealing step, cold rolling to final thickness is performed according to step F. If no intermediate annealing step is performed, step F replaces steps D and E, and cold rolling to final thickness is performed without intermediate annealing.

[0089] In step F, the degree of rolling during cold rolling after hot rolling or after the last intermediate annealing of the final thickness is limited to less than 25%, preferably less than 22% or particularly preferably less than 18% in order to obtain the necessary rolled product properties.

[0090] Alternatively, hot rolling can be followed by cold rolling to final thickness with at least one optional intermediate annealing in the form of soft annealing at 250 °C and 450 °C according to steps D, E and F'. In contrast to F, cold rolling to final thickness according to step F' is not limited to a maximum degree of stripping. Rather, stripping degrees of at least 25% or preferably at least 28% are used. In this alternative, re-annealed microstructures in the rolled product to final thickness are achieved by final annealing in a temperature range of 150 °C to 280 °C according to step G, so that the desired properties are achieved. During the final annealing, the target metal temperature is maintained for at least 0.5 hours, preferably at least 1 hour.

[0091] To produce the battery cell housings 11, 21, 31, a rolled product made of an aluminum alloy undergoes several forming steps. Fig. 5 shows a schematic flow diagram of the production of a cup-shaped battery cell housing, for example cylindrical or prismatic battery cell housings, starting from a rolled product in the form of a strip or sheet. The rolled product is provided in step 1 and subjected to a first forming step, for example by a first deep-drawing stage according to step 2. Further optional deep-drawing or ironing stages 3, 4 can follow until a cup-shaped battery cell housing can be provided in step 5. This can then be subjected to further work steps until the finished battery cell is produced. Due to the high safety requirements for battery cell housings, the forming steps are carried out on production equipment specifically tailored to the selected aluminum alloy.The production resources currently predominantly used are designed for rolled products consisting of an aluminum alloy of type AA3003.

[0092] Examples of the rolled product according to the invention and rolled products as comparative examples were manufactured from different aluminum alloys and their suitability for use in the aforementioned production equipment was tested. It was assumed that the rolled products, upon reaching the specified mechanical parameters for the yield strength R P o.2, tensile strength R m and elongation Aso are suitable for use in the predominantly existing production equipment for an aluminum alloy of type AA3003.

[0093] Table 1 initially shows the alloy compositions of the working examples (Ex.) and the comparative examples (Cf. J.). Each individual example was manufactured using the specific process parameters specified in Table 2. All temperatures are to be understood as "peak metal temperature" (PMT), i.e. the maximum temperature of the metal. During homogenization, the residence time at homogenization temperature was at least 1 h. Homogenization can take place in a separate annealing process or be integrated into the preheating. When homogenization is integrated into the preheating, the homogenization temperature is first set and held for at least 1 h. The rolling ingot is then brought to the preheating temperature. During preheating of the rolling ingot, the rolling ingot is fed into the rolling process when the preheating temperature is reached. In all examples, the preheating temperature at the beginning of hot rolling was between 390 and 550 °C.The final hot-rolled strip thickness is the final hot-rolled strip thickness. The final hot-rolled strip temperature is the temperature of the hot-rolled strip after the last hot-rolling pass. Finally, Table 3 shows the achieved mechanical properties. All mechanical parameters such as yield strength R. P o.2, tensile strength R m and elongation Aso were obtained according to EN ISO 6892-1:2019.

[0094] Comparative Example No. 3 corresponds to a reference rolled product made of an aluminum alloy of type AA3003. Examples Nos. 1, 6 to 8, and 11 to 12 are rolled products according to the teachings of the invention. These comprise an aluminum alloy that, in contrast to the primary aluminum-based reference rolled product No. 3, allows for high recycling content.

[0095] Example No. 1 was produced in the H12 temper, i.e., without reannealing. The rolled ingot was subjected to homogenization according to the specifications outlined above. The final thickness reduction after intermediate annealing was 12%. Example No. 1 achieves the mechanical properties according to the invention and, due to its composition, can be manufactured with high recycled content and used on existing battery cell housing production equipment.

[0096] Although Example No. 2, produced from an identically homogenized rolling ingot, has an aluminum alloy meeting the features of patent claim 1, the rolled product was cold-rolled with an excessively high final thickness reduction of 30% after intermediate annealing. As a result, the comparative rolled product produced in this way does not achieve the desired mechanical properties. It is significantly too strong and has too low an elongation Aso.

[0097] Although reference material No. 3 achieves all mechanical properties, as already explained, it can only be produced through closed material cycles with a high proportion of recycled material of at least 30%.

[0098] The rolled products according to Comparative Examples 4 and 5 have significantly excessive magnesium contents and are therefore prone to severe strain hardening during cold rolling. The strain hardening was so severe that it could not be sufficiently reduced even during the reannealing at 180 °C for 16 hours and at 250 °C for 1 hour. Comparative Examples 4 and 5 are therefore not suitable for use with current production equipment for the manufacture of battery cell casings.

[0099] Examples 6 to 8 have two different alloy compositions, while examples 6 and 7 have identical compositions. All three examples were produced using different manufacturing processes according to the present invention and achieve the claimed mechanical properties in the H22 (Nos. 6 and 7) and H24 (No. 8) tempers.

[0100] The rolled product of Comparative Example No. 9 comprises an aluminum alloy with a composition that meets the required contents. During cold rolling after intermediate annealing, the final thickness reduction was 30%, so the mechanical properties of the invention were not achieved. The rolled product exhibited too low an elongation Aso and too high a tensile strength R. m Further processing on existing production equipment for the manufacture of battery cell casings is therefore not possible.

[0101] Comparative Example No. 10 also comprises an aluminum alloy according to the present invention, but was converted to the soft state O during the final annealing, so that Comparative Example No. 10 also does not meet the requirement for battery cell casing production.

[0102] Working examples 11 and 12 comprise an aluminum alloy composition according to the invention and were produced using the manufacturing process according to the invention. The corresponding rolled products in the reannealed H24 and H22 tempers exhibited all the required mechanical properties and can be used on existing production equipment for the manufacture of battery cell casings.

[0103] 5

[0104] Table 1

[0105] * All figures in wt.%, remainder aluminum and unavoidable impurities, individually max. 0.05 wt.%, in total 0.15 wt.%

[0106] Table 2

[0107] Table 3

Claims

Patent claims 1. Rolled product made of an aluminum alloy for producing a battery cell housing comprising an aluminum alloy with the following alloying constituents in wt.%: 0.1% < Si < 0.7%, 0.2% < Fe < 0.8%, Cu < 0.6%, 0.3% < Mn < 1.5%, 0.025% < Mg < 0.60%, preferably 0.01 wt% < Mg < 0.60 wt%, Cr < 0.25%, Zn < 0.5%, Ti < 0.2%, Remainder Al and unavoidable impurities, individually maximum 0.05%, in total maximum 0.15%, whereby the rolled product has a tensile strength R m of at least 135 MPa to a maximum of 210 MPa, preferably a maximum of 185 MPa, a yield strength R P o,2 of more than 125 MPa up to a maximum of 180 MPa, preferably a maximum of 165 MPa, and an elongation Aso of more than 5%, preferably more than 7%.

2. Rolled product according to claim 1, characterized in that the aluminum alloy has the following alloying constituents in wt.%: 0.2% < Si < 0.60%, preferably 0.35% < Si < 0.55%, 0.2% < Fe < 0.65%, preferably 0.25% < Fe < 0.55%, Cu < 0.3%, preferably 0.1% < Cu < 0.2%, 0.3% < Mn < 1.3%, preferably 0.4% < Mn < 1.1%, 0.05% < Mg < 0.50%, preferably 0.1% < Mg < 0.45%, Cr < 0.1%, preferably Cr < 0.05%, 0.0050% < Zn < 0.30%, preferably 0.02% < Zn < 0.30%, 0.005% < Ti < 0.1%, preferably 0.005% < Ti < 0.05%, Remainder Al and unavoidable impurities, individually maximum 0.05%, in total maximum 0.15%.

3. Rolled product according to claim 1 or 2, characterized in that the proportion of recycled metal in the rolled product is at least 30 wt.%, preferably at least 50 wt.%, particularly preferably at least 70 wt.%.

4. Rolled product according to one of claims 1 to 3, characterized in that the rolled product has the tempering state H12, H24, H22, H34 or H32.

5. Rolled product according to one of claims 1 to 4, characterized in that the rolled product has a thickness of 0.1 mm to 2.0 mm, preferably 0.25 mm to 1.5 mm and particularly preferably from 0.35 mm to 1.2 mm.

6. Rolled product according to one of claims 1 to 5, characterized in that the rolled product has a degreased surface with surface tensions of more than 30 mN / m, preferably more than 32 mN / m, particularly preferably more than 34 mN / m.

7. A process for producing a rolled product from an aluminum alloy according to claims 1 to 6, comprising the following process steps: - Providing a rolling ingot made of an aluminium alloy with the following Composition in wt%: 0.1% < Si < 0.7%, 0.2% < Fe < 0.8%, Cu < 0.6%, 0.3% < Mn < 1.5%, 0.025% < Mg < 0.60%, preferably 0.05% < Mg < 0.55%, Cr < 0.25%, Zn < 0.5%, Ti < 0.2%, Remainder Al and unavoidable impurities, individually maximum 0.05%, in total maximum 0.15% - optional homogenization of the rolling ingot at 480 °C to 625 °C, preferably at 550 °C to 620 °C for at least 0.1 hours, preferably for at least 0.25 hours, more preferably at least 0.5 hours, - Hot rolling of the rolling ingot to a hot strip thickness of 2 mm to 10 mm with a hot strip final temperature between 250 °C and 450 °C, - cold rolling of the hot strip to final thickness with at least one optional intermediate annealing, preferably in the form of soft annealing at 250 °C to 450 °C, wherein the degree of rolling during cold rolling without intermediate annealing to final thickness or the degree of rolling during cold rolling after the last intermediate annealing is less than 25%, preferably less than 22% or particularly preferably less than 18%.

8. Method according to claim 7, characterized in that alternatively, after the hot rolling, cold rolling to final thickness with at least one optional intermediate annealing, preferably in the form of a soft annealing at 250 °C to 450 °C is carried out, wherein the degree of rolling during cold rolling without intermediate annealing to final thickness or the degree of rolling during cold rolling after the last intermediate annealing is at least 25%, preferably at least 28% and a final annealing in a temperature range of 150 °C to 280 °C to adjust the reannealed microstructure in the rolled product to the final thickness.

9. Use of a rolled product according to claims 1 to 6, preferably produced by a method according to claim 7 or 8, for a battery cell housing.

10. Use according to claim 9, characterized in that the battery cell housing is a housing of a secondary cell, preferably a lithium-ion secondary cell, a sodium-ion secondary cell or a solid-state secondary cell.

11. Use according to claim 9 or 10, characterized in that the battery cell housing has a prismatic design, a cylindrical design or a pouch design.

12. Use according to one of claims 9 to 11, characterized in that the rolled product made of an aluminum alloy for use in a battery cell housing is subjected to a plurality of forming steps, preferably deep drawing and / or ironing.

13. Use according to one of claims 9 to 12, characterized in that the battery cell housing is sealed gas-tight by a material-to-material joining process during the assembly of the battery cell.

14. Battery cell housing made from a rolled product according to claim 1 to 5, wherein the battery cell housing has a prismatic shape, a cylindrical design or a pouch design.

15. Battery cell housing according to claim 14, characterized in that the battery cell housing has at least one formed region which is obtained by forming, preferably by deep drawing and / or ironing, a rolled product made of aluminum alloy according to one of claims 1 to 6.

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