Aluminum alloy sheet for lithium ion battery and method for producing same

Abstract

To provide a high-strength aluminum alloy sheet for a lithium ion battery, which can be applied to a next-generation high-capacity battery material.SOLUTION: The aluminum alloy material contains, by mass%, 0.1 to 0.4% of Si, 0.05 to 0.70% of Fe, 0.50 to 0.70% of Cu, 0.8 to 1.6% of Mn, and 0.50 to 0.90% of Mg, and contains 0.005 to 0.150% of Ti, or 0.0001 to 0.150% of Ti and 0.0001 to 0.0500% of B, with the balance being Al and an inevitable impurity, wherein the total content of Fe and Mn is 1.80 mass% or less, and the tensile strength is 230MPa or more.SELECTED DRAWING: None

Description

[Technical Field]

[0001] The present invention relates to a high-strength aluminum alloy plate used in lithium-ion batteries and a method for producing the same. [Background technology]

[0002] Electric vehicles, electric motorcycles, mobile phones, and personal computers powered by lithium-ion secondary batteries are widely used. Among these, demand for electric vehicles as environmentally friendly vehicles has been increasing in recent years. Aluminum alloy sheets are used as materials for lithium-ion secondary batteries, and are required to have formability, moderate strength, and the like.

[0003] For example, an aluminum alloy sheet is known in which a 3000 series aluminum alloy, or an aluminum alloy obtained by adding Mg to a 3000 series aluminum alloy, is co-containing with appropriate amounts of Zr, Ti, and / or B (see Patent Document 1). This aluminum alloy sheet is said to have a high 45° earing ratio when deep-drawn into a cylindrical container even at a low rolling reduction, to have excellent product yield in rectangular-draw and ironing, to have good rectangular-draw and ironing formability for thin sheets, and to have excellent productivity with no cracking even when the pulse laser welding speed is increased.

[0004] Another known aluminum alloy sheet is an aluminum alloy sheet for battery lids used in forming one-piece explosion-proof valves, which contains 1.05 to 1.50 mass% Fe, 0.30 to 0.70 mass% Mn, 0.002 to 0.15 mass% Ti, and less than 0.04 mass% B, with the balance being Al and impurities, and has a component composition in which the Fe / Mn ratio is regulated to 1.8 to 3.5, and the impurities are regulated to less than 0.20 mass% Si, less than 0.03 mass% Cu, less than 0.05 mass% Mg, and less than 0.03 mass% V, and which has an electrical conductivity of 53.0% IACS or more, a 0.2% proof stress of 40 MPa or more, an elongation of 40% or more, a recrystallized structure, and an elongation of 5.0% or more after cold rolling at a reduction of 80% and after cold rolling at a reduction of 90% (see Patent Document 2). This aluminum alloy plate is said to have excellent heat dissipation, deformation resistance, and formability, as well as little fluctuation in operating pressure and excellent resistance to repeated fatigue. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2004-197172 [Patent Document 2] International Publication No. 2019 / 111970 Summary of the Invention [Problem to be solved by the invention]

[0006] Aluminum alloy sheets used for the cases and lids of lithium-ion secondary batteries require basic performance such as formability, but for next-generation batteries, there is an increasing demand for higher strength and thinner walls.

[0007] The aluminum alloy sheet described in Patent Document 1 contains Zr. During previous pulse laser welding, Zr refined grains during solidification of the weld, making Zr essential for preventing weld cracking. However, with subsequent improvements in welding technology, Zr is no longer an essential element, as it is now possible to join welds using continuous welding. Furthermore, Zr can inhibit grain refinement by Ti and B during slab casting, which can lead to slab cracking. Therefore, castability tends to be improved without the addition of Zr. For these reasons, the aluminum alloy described in Patent Document 1, which contains Zr, may not be able to guarantee excellent castability.

[0008] On the other hand, the aluminum alloy sheet for battery lids described in Patent Document 2 contains Mn on the premise that it contains Fe. In this aluminum alloy sheet, the inclusion of Fe improves formability due to increased local elongation and realizes excellent work softening properties, and the addition of Mn realizes improved pressure resistance, improved softening resistance, and improved high-temperature creep properties. However, the aluminum alloy of Patent Document 2 has a base metal tensile strength of about 110 MPa, and in view of the recent demand for higher strength, there is room for further improvement in strength such as base metal tensile strength.

[0009] As described above, basic performance such as formability is still required for aluminum alloy sheets for lithium ion secondary batteries. However, for next-generation high-capacity battery materials, particularly, higher strength is increasingly required.

[0010] The present invention has been made in consideration of the above circumstances, and an object of the present invention is to provide an aluminum alloy sheet for high-strength lithium-ion batteries, which has excellent formability and is also applicable to next-generation high-capacity battery materials. [Means for solving the problem]

[0011] The aluminum alloy sheet for lithium ion batteries according to the present invention comprises: In mass%, it contains Si: 0.1 to 0.4%, Fe: 0.05 to 0.70%, Cu: 0.50 to 0.70%, Mn: 0.8 to 1.6%, and Mg: 0.50% to 0.90%, Contains Ti: 0.005 to 0.150%, or Ti: 0.0001 to 0.150% and B: 0.0001 to 0.0500 mass%, the balance being Al and unavoidable impurities, The total content of Fe and Mn is 1.80 mass% or less, It is characterized by a tensile strength of 230 MPa or more. [Effects of the Invention]

[0012] In the aluminum alloy sheet for lithium ion batteries according to the present invention, by suitably adjusting not only the contents of Fe and Mn in particular but also the total content of these elements (Fe, Mn), it is possible to provide an aluminum alloy sheet for lithium ion batteries with high strength that can also be used for next-generation high-capacity battery materials while ensuring formability. DETAILED DESCRIPTION OF THE INVENTION

[0013] <Aluminum alloy plate for lithium-ion batteries> The aluminum alloy sheet for a lithium-ion battery according to an embodiment of the present invention (hereinafter sometimes referred to as "the present embodiment") has the following features: In mass%, it contains Si: 0.1 to 0.4%, Fe: 0.05 to 0.70%, Cu: 0.50 to 0.70%, Mn: 0.8 to 1.6%, and Mg: 0.50% to 0.90%, Contains Ti: 0.005 to 0.150%, or Ti: 0.0001 to 0.150% and B: 0.0001 to 0.0500 mass%, the balance being Al and unavoidable impurities, The total content of Fe and Mn is 1.80 mass% or less, It is characterized by a tensile strength of 230 MPa or more.

[0014] Generally, increasing the strength of an aluminum alloy sheet results in a problem of reduced formability. Specifically, when Mn is added to an aluminum alloy sheet, Mn dissolves in the matrix to promote solid-solution strengthening, thereby achieving high strength (assessed by tensile strength). However, this results in coarsening of Al-Fe-Mn intermetallic compounds or an increase in the amount of such compounds. Thus, excessively high strength achieved through solid-solution strengthening actually results in a decrease in formability. Furthermore, when cold-rolling an aluminum alloy sheet, high strength can be achieved by increasing the reduction rate and promoting work hardening, but excessively high strength achieved through work hardening actually results in a decrease in formability.

[0015] Therefore, the present inventors have found that, in order to make the tensile strength of the aluminum alloy sheet 230 MPa or more, the Mn content should be 0.80 mass% or more and the rolling reduction should be 20% or more, while in order to suppress coarsening of Al-Fe-Mn intermetallic compounds with the aim of maintaining formability, the total content of Fe and Mn should be controlled to 1.80 mass% or less. An aluminum alloy sheet for lithium-ion batteries according to this embodiment, which is based on such finding, will be described in detail below.

[0016] The aluminum alloy plate for lithium ion batteries of the present embodiment is not particularly limited in its use as long as it is used for lithium ion batteries, and can be used for, for example, battery lids, cases, and other battery components.

[0017] The constituent elements of the high-strength aluminum alloy sheet of this embodiment, Si, Fe, and Mn, impart strength to the aluminum alloy sheet, and also refine the recrystallized structure and impart DI formability by finely dispersing and forming intermetallic compounds such as Al-Fe, Al-Mn, and Al-(Fe, Mn)-Si. Furthermore, if the Si, Fe, or Mn content is less than the lower limit of the composition range described below, the above-mentioned effects are insufficient and blister resistance is poor. On the other hand, if the Si, Fe, or Mn content exceeds the upper limit of the composition range described below, coarse compounds are formed, degrading DI formability and resulting in poor weldability.

[0018] Si:0.1~0.4% by mass Si is an essential element for imparting strength and formability to an aluminum alloy sheet. In this embodiment, the Si content is 0.1 to 0.4 mass%. If the Si content is less than 0.1 mass%, sufficient strength and formability cannot be obtained, and if the Si content exceeds 0.4 mass%, coarse intermetallic compounds such as Al-(Fe, Mn)-Si crystallize during ingot casting, resulting in reduced formability and weldability. The Si content is more preferably 0.15 to 0.35 mass%, and extremely preferably 0.2 to 0.3 mass%.

[0019] Fe:0.05~0.70% by mass Fe is an essential element for imparting strength and formability to aluminum alloy sheets. To obtain sufficient strength and formability, the Fe content is set to 0.05% by mass or more. If the Fe content exceeds 0.7% by mass, the size and number of Fe-based intermetallic compounds increase, resulting in reduced formability and weldability. Therefore, the Fe content is set to 0.70% by mass or less. The Fe content is preferably 0.10 to 0.65% by mass, more preferably 0.12 to 0.60% by mass, and most preferably 0.15 to 0.50% by mass.

[0020] Mn:0.8~1.6% by mass Mn is an essential element for imparting strength, softening resistance, and formability to an aluminum alloy sheet. To obtain sufficient strength, softening resistance, and formability, the Mn content is set to 0.8% by mass or more. If the Mn content exceeds 1.6% by mass, the strength becomes too high, which may result in a decrease in formability. The Mn content is preferably 0.9 to 1.5% by mass, more preferably 1.0 to 1.4% by mass, and most preferably 1.1 to 1.2% by mass.

[0021] Mg:0.50~0.90% by mass Mg is an essential element for imparting strength to an aluminum alloy sheet. To obtain sufficient strength, the Mg content is set to 0.50% by mass or more. If the Mg content exceeds 0.90% by mass, the strength may become too high, resulting in a decrease in formability. The Mg content is preferably 0.55 to 0.85% by mass, more preferably 0.60 to 0.80% by mass, and most preferably 0.65 to 0.75% by mass.

[0022] Cu:0.50~0.70% by mass Cu is an essential element for imparting strength to an aluminum alloy sheet. To obtain sufficient strength, the Cu content is set to 0.50% by mass or more. If the Cu content exceeds 0.70% by mass, the strength may become too high, resulting in a decrease in formability. The Cu content is preferably 0.51 to 0.65% by mass, more preferably 0.52 to 0.63% by mass, and most preferably 0.53 to 0.60% by mass.

[0023] Ti: 0.005 to 0.150 mass%, or Ti: 0.0001 to 0.150 mass% and B: 0.0001 to 0.0500 mass% Ti and B generate various intermetallic compounds that act as solidification nuclei, imparting strength and formability to the aluminum alloy sheet. In this embodiment, when only Ti is contained, the Ti content is 0.005 to 0.150 mass%, and when both Ti and B are contained, the Ti content is 0.0001 to 0.150 mass% and the B content is 0.0001 to 0.0500 mass%. If the Ti and B contents are below their respective lower limits, sufficient strength and formability cannot be obtained. On the other hand, if the Ti content exceeds the upper limit, coarse intermetallic compounds such as TiAl3 crystallize during ingot casting, resulting in reduced formability. On the other hand, if the B content exceeds the upper limit, depending on the Ti content, Ti-B compounds are likely to stabilize and become TiB2, which reduces the grain refinement effect and may cause TiB2 to settle in the furnace and accumulate on the hearth. In either case, the Ti content is preferably 0.010 to 0.140 mass%, more preferably 0.015 to 0.130 mass%, and most preferably 0.020 to 0.120 mass%, and the B content is preferably 0.0010 to 0.0400 mass%, more preferably 0.0015 to 0.0300 mass%, and most preferably 0.0020 to 0.0200 mass%.

[0024] Total content of Fe and Mn: 1.80% by mass or less In the aluminum alloy sheet of this embodiment, if the total content of Fe and Mn exceeds 1.80 mass%, coarse crystals are generated in the alloy sheet, and formability deteriorates. Therefore, in order to maintain formability, the total content of Fe and Mn is controlled to 1.80 mass% or less. The total content of Fe and Mn is preferably 1.75 mass% or less, more preferably 1.72 mass% or less, and most preferably 1.70 mass% or less.

[0025] Inevitable impurities Incidental impurities are uncontrolled elements that are inevitably mixed in from raw metals, returned materials, etc. Acceptable contents of these elements include, for example, V: less than 0.03% by mass, Cr: less than 0.20% by mass, Zn: less than 0.20% by mass, Ni: less than 0.10% by mass, Ga: less than 0.05% by mass, (each of Pb, Bi, Sn, Na, Ca, and Sr): less than 0.02%, and other elements, such as Co, Nb, Mo, and W: less than 0.05% by mass. Even if uncontrolled elements are contained within these ranges, none of the above-mentioned effects of the present invention are impaired.

[0026] Does not contain Zr The component composition of the aluminum alloy plate of this embodiment has been described above, but one of the features of the aluminum alloy plate of this embodiment is that it does not contain Zr, unlike the aluminum alloy plate described in Patent Document 1. In this embodiment, Zr is basically an uncontrolled element, but since the aluminum alloy plate does not contain Zr, there is no need to set the casting temperature, which will be described later, to a relatively high temperature, so that rapid cooling occurs during solidification, and Zr does not inhibit the effect of a refiner such as Ti, so that castability (evaluated by the presence or absence of casting cracks) does not deteriorate.

[0027] Tensile strength of 230 MPa or more Aluminum alloy sheets for next-generation high-capacity lithium-ion batteries are required to have high strength. In the aluminum alloy sheet of this embodiment, the tensile strength (MPa) of the base material is used as an index for evaluating strength. The tensile strength is 230 MPa or more, preferably 260 MPa or more, more preferably 280 MPa or more, and most preferably 300 MPa or more.

[0028] It should be noted that this tensile strength (230 MPa or more) is not a performance that can be realized only by the composition of the above-mentioned elements, but is a performance that can be achieved by the composition and the manufacturing method described below (particularly, a cold rolling reduction of 20% or more). The manufacturing method will be described later.

[0029] <Method of manufacturing aluminum alloy sheet for lithium-ion batteries> Hereinafter, a method for producing the above-described "aluminum alloy sheet for lithium ion batteries" will be described in detail. Note that the method for producing the aluminum alloy sheet for lithium ion batteries of the present embodiment described below is merely an example, and is not intended to be limited to the method described below.

[0030] The method for producing an aluminum alloy plate for a lithium ion battery of the present embodiment includes: a slab casting step of obtaining an ingot from a molten aluminum alloy having the above-mentioned component composition by a semi-continuous casting method; a homogenization treatment step including homogenizing the ingot at a holding temperature of 500 to 600 ° C. for a holding time of 1 hour or more; a hot rolling step of hot rolling the ingot after the homogenization treatment step to obtain a hot rolled plate; a cold rolling step of cold rolling the hot rolled sheet at a rolling reduction rate of 20% or more; Each step will be described in detail below.

[0031] Slab casting process Ingots are produced by semi-continuous casting (DC casting). In typical semi-continuous casting, the thickness of the ingot is generally around 400mm to 600mm, so the solidification cooling rate at the center of the ingot is around 1°C / sec. For this reason, when semi-continuous casting molten aluminum alloys with particularly high Fe and Mn contents, relatively coarse intermetallic compounds such as Al(Fe·Mn) and α-Al-(Fe·Mn)-Si tend to crystallize out of the molten aluminum alloy at the center of the ingot.

[0032] Although it depends on the width and thickness of the ingot, the casting speed in semi-continuous casting is usually 50 to 70 mm / min, taking productivity into consideration. Furthermore, when performing inline degassing, depending on degassing conditions such as the inert gas flow rate, considering the actual residence time of the molten metal in the degassing treatment tank, the lower the flow rate of the molten aluminum (the amount of molten metal supplied per unit time), the more efficient the degassing in the tank and the more likely it is that the amount of hydrogen gas in the ingot will be reduced. For these reasons, although it depends on factors such as the number of castings, it is preferable to limit the casting speed to 30 to 50 mm / min in order to reduce the amount of hydrogen gas in the ingot. A casting speed of less than 30 mm / min is undesirable because it reduces productivity. On the other hand, a casting speed of 50 mm / min or less reduces the slope of the sump (the interface between the solid and liquid phases) in the ingot, preventing casting cracks. The casting speed is more preferably 35 to 48 mm / min, and most preferably 40 to 45 mm / min.

[0033] Homogenization process: 500-600℃ x 1 hour or more The homogenization treatment of the ingot obtained by semi-continuous casting is a treatment to eliminate casting segregation by holding it at a high temperature to facilitate rolling, and it is necessary to hold it at 500 to 600°C for at least 1 hour. If the holding temperature is too low (less than 500°C) or the holding time is too short (less than 1 hour), the size of the precipitates becomes small, and the recrystallized grains during intermediate annealing described below become coarse, which ultimately leads to a decrease in the strength of the aluminum alloy sheet. On the other hand, if the heating temperature is too high (more than 600°C), there is a risk of partial melting of the ingot, so-called burning.

[0034] The holding temperature in the homogenization treatment is preferably 520° C. or higher and 590° C. or lower, more preferably 525° C. or higher and 585° C. or lower, and most preferably 530° C. or higher and 580° C. The holding time in the homogenization treatment is preferably 1.5 hours or longer, more preferably 2 hours or longer, and most preferably 3 hours or longer.

[0035] Hot rolling process, cold rolling process before intermediate annealing, intermediate annealing process In this embodiment, after the homogenization treatment step, a hot rolling step, a cold rolling step before intermediate annealing, and an intermediate annealing step are performed. However, the cold rolling step before intermediate annealing and the intermediate annealing step, which are performed for strength adjustment, may be omitted.

[0036] The cold rolling step before intermediate annealing and the intermediate annealing step can be omitted when the thickness of the aluminum alloy plate to be finally obtained is relatively large, for example, when an aluminum alloy plate having a thickness of about 2 mm is produced.

[0037] In contrast, when the cold rolling step before the intermediate annealing and the intermediate annealing step are performed without omitting them, the thickness of the aluminum alloy plate to be finally obtained is relatively small, for example, this applies to the case of producing an aluminum alloy plate with a plate thickness of about 0.6 mm.

[0038] In this embodiment, the detailed conditions of the above-mentioned three steps (hot rolling step, cold rolling step before intermediate annealing, and intermediate annealing step) are not specified, but they can be carried out, for example, as follows.

[0039] In the hot rolling process, although it depends on the model of the hot rolling mill, the ingot removed from the soaking furnace is usually hot rolled through several rolling passes to produce a hot-rolled sheet of a specified thickness (for example, about 4 to 8 mm) and wound into a coil.

[0040] In the cold rolling process before intermediate annealing, the coil wound in the hot rolling mill is passed through a cold rolling mill, and cold rolling is usually performed in multiple passes. Since work hardening occurs due to the plastic strain introduced by cold rolling, an annealing treatment (intermediate annealing process) is performed as necessary.

[0041] Since the intermediate annealing step is also a softening treatment, the cold-rolled coil may be inserted into a batch furnace and held at a temperature of 300 to 400°C for one hour or more, depending on the material. If the holding temperature is less than 300°C, softening may not be promoted. The holding temperature may be 310°C or higher, 320°C or higher, or 330°C or higher. On the other hand, if the holding temperature exceeds 400°C, productivity may decrease. The holding temperature may be 390°C or lower, 380°C or lower, or 370°C or lower.

[0042] The cold-rolled sheet is thus subjected to intermediate annealing. The intermediate annealing step applied to the cold-rolled sheet described above may be continuous annealing or batch annealing.

[0043] Cold rolling process after hot rolling or cold rolling process after intermediate annealing In this embodiment, after the above-mentioned hot rolling (when the cold rolling step before intermediate annealing and the intermediate annealing step are not performed) or after the above-mentioned intermediate annealing step, a cold rolling step is further performed to adjust the strength of the base material (specifically, to improve the tensile strength).

[0044] In both the cold rolling process after hot rolling and the cold rolling process after intermediate annealing, the annealed sheet is cold rolled at a reduction rate of 20% or more to produce a base metal with a tensile strength of 230 MPa or more. If the reduction rate is less than 20%, it is difficult to obtain a strength of 230 MPa, assuming the above-mentioned composition of the aluminum alloy sheet of this embodiment. Since the required strength and formability vary depending on the case, there is no particular upper limit for the reduction rate, but as long as it is 80% or less, it is possible to achieve both the desired strength and formability. Note that when higher formability is required, the reduction rate is preferably 65% ​​or less. Note that the reduction rate is preferably 25 to 65%, more preferably 30 to 60%, and extremely preferably 35 to 55%. [Example]

[0045] The effects of the present invention will be demonstrated by Examples 1 and 2 shown below, but the present invention is not limited to Examples 1 and 2 shown below. Examples 1 and 2 shown below are experimental examples in which the composition and the like of the high-strength aluminum alloy sheet for lithium-ion batteries according to the present invention were specified by laboratory tests.

[0046] (Example 1: Evaluation of strength and moldability depending on composition) Preparation of simulated materials Each of the eight ingots (7.5 kg) with compositions shown in Table 1 below was placed in a #30 crucible, which was then heated in a small electric furnace to melt the ingots. A lance was then inserted into the molten metal, and N2 gas was blown in at a flow rate of 2.0 L / sec for 6 minutes to degas the ingots. The melt was then allowed to settle for 15 minutes, after which slag that had risen to the surface was removed with a stirring rod. The crucible was then removed from the small electric furnace, and the molten metal was poured into a mold with internal dimensions of 200 × 200 × 50 mm to produce ingots. Test materials with compositions A to H (Invention Examples 1 to 6 and Comparative Examples 1 and 2) were obtained from the molten metal in each crucible. Disk samples of these test materials were then subjected to compositional analysis by optical emission spectroscopy. The results are shown in Table 1.

[0047] [Table 1]

[0048] Each ingot was chamfered 5 mm on both sides to a thickness of 40 mm, and then homogenized at 590°C for 3 hours and 480°C for 2 hours. The hot-rolled sheets were then hot-rolled to obtain 9.0 mm thick hot-rolled sheets. Each hot-rolled sheet was then cold-rolled to obtain 1.5 mm thick cold-rolled sheets A1-H1 and 2.0 mm thick cold-rolled sheets A2-H2, respectively. Furthermore, these cold-rolled sheets A1-H1 and A2-H2 were inserted into an annealer and subjected to an intermediate annealing treatment at 390°C for 1 hour, simulating batch annealing, to obtain annealed sheets A1-H1 and A2-H2.

[0049] Next, the annealed sheet A1 having a thickness of 1.5 mm was cold rolled at a rolling reduction of 60% to obtain test material A160, and the annealed sheet A2 having a thickness of 2.0 mm was cold rolled at a rolling reduction of 70% to obtain test material A270.

[0050] Similarly, annealed sheets B1 to H1 and annealed sheets B2 to H2 were cold rolled at a reduction of 60% or 70% to obtain test materials B160, B270, C160, C270, . . . , H160, and H270.

[0051] Tensile test JIS No. 5 test pieces were taken from each of the obtained test materials (A160, A270, B160, B270, C160, C270, D160, D270, E160, E270, F160, F270, G160, G270, H160, H270) so that the tensile direction was parallel to the rolling direction. Tensile tests were conducted in accordance with JIS Z2241 to determine the tensile strength (MPa), elongation (elongation at break) (%), and 0.2% yield strength (MPa).

[0052] Bending test Test pieces were taken from each test material so that they were parallel to the rolling direction, and a 90° bending test was performed using the V-block method in accordance with JIS Z 2248 to check for the presence of cracks on the outside of the curved portion of the test piece. The test was performed with an inner radius of 2 mm (R2). After visual inspection, those without cracks were marked with a ◯, and those with cracks were marked with an ×.

[0053] In assessing formability, examples in which the bending test results were good at both 60% and 70% reduction were given a formability evaluation of ◯, examples in which the bending test results were good at 60% reduction but poor at 70% reduction were given a formability evaluation of △, and examples in which the bending test results were poor at both 60% and 70% reduction were given an x. The results are shown in Table 2.

[0054] [Table 2]

[0055] According to Table 2, in Examples 1 to 6, a tensile strength of 230 MPa was achieved with a predetermined composition range and a predetermined reduction (20% or more), and the bending test results were also good when the reduction was 60%.

[0056] On the other hand, the formability evaluation was poor in Comparative Example 1 because the Cu content was outside the predetermined composition range, and similarly, the formability evaluation was poor in Comparative Example 2 because the Mg content was outside the predetermined composition range.

[0057] (Example 2: Evaluation of castability by composition) Next, the castability of composition A (invention example 1) and composition I (comparison example 3) shown in Table 3 below was compared and evaluated.

[0058] [Table 3]

[0059] For both Composition A (Invention Example 1) and Composition I (Comparative Example 3), molten aluminum alloy was melted in a melting furnace and then subjected to semi-continuous casting (DC casting) to obtain an ingot measuring 1070 mm in width, 560 mm in thickness, and 3250 mm in length. The casting temperature for Inventive Example 1 was 680 to 700°C, while the casting temperature for Comparative Example 3 was 700 to 720°C. The reason for the different casting temperatures in both examples is that Comparative Example 3, which contains Zr, crystallizes coarse crystals at low casting temperatures, so it is necessary to increase the casting temperature.

[0060] Comparing Example 1 with Comparative Example 3, no casting cracks were observed in Example 1. Since Example 1 does not contain Zr, it is not necessary to raise the casting temperature so much, and so rapid cooling does not occur during solidification, which is thought to be why no casting cracks occurred. In addition, since Example 1 does not contain Zr, the effect of grain refiners such as Ti is not inhibited, which is also thought to be the reason why castability did not deteriorate.

[0061] In contrast, casting cracks occurred in Comparative Example 3, which contained Zr. This is thought to be because the casting temperature in Comparative Example 3 was high due to the inclusion of Zr, which resulted in rapid cooling during solidification, and Zr inhibited the effects of refiners such as Ti, resulting in poor castability.

Claims

1. In mass%, it contains Si: 0.1 to 0.4%, Fe: 0.05 to 0.70%, Cu: 0.50 to 0.70%, Mn: 0.8 to 1.6%, and Mg: 0.50% to 0.90%, Contains Ti: 0.005 to 0.150%, or Ti: 0.0001 to 0.150% and B: 0.0001 to 0.0500 mass%, the balance being Al and unavoidable impurities; The total content of Fe and Mn is 1.80 mass% or less, An aluminum alloy plate for lithium-ion batteries, characterized in that it has a tensile strength of 230 MPa or more.

2. 2. The aluminum alloy plate for lithium ion batteries according to claim 1, wherein the aluminum alloy plate contains, in mass%, Fe: 0.50% or less, Cu: 0.60% or less, and Mn: 1.2% or less.

3. The method for producing an aluminum alloy sheet for a lithium ion battery according to claim 1 or 2, a slab casting step of obtaining an ingot from a molten aluminum alloy having the component composition according to claim 1 or 2 by a semi-continuous casting method; a homogenization treatment step including homogenizing the ingot at a holding temperature of 500 to 600°C for a holding time of 1 hour or more; a hot rolling step of hot rolling the ingot after the homogenization treatment step to obtain a hot rolled plate; a cold rolling process of cold rolling the hot rolled sheet at a rolling reduction rate of 20% or more; A method for producing an aluminum alloy plate for a lithium ion battery, comprising:

4. The method for producing an aluminum alloy sheet for a lithium ion battery according to claim 1 or 2, a slab casting step of obtaining an ingot from a molten aluminum alloy having the component composition according to claim 1 or 2 by a semi-continuous casting method; a homogenization treatment step including homogenizing the ingot at a holding temperature of 500 to 600°C for a holding time of 1 hour or more; a hot rolling step of hot rolling the ingot after the homogenization treatment step to obtain a hot rolled plate; a cold rolling step before intermediate annealing in which the hot-rolled sheet is subjected to cold rolling before intermediate annealing to obtain a cold-rolled sheet; an intermediate annealing step in which the cold-rolled sheet is annealed to obtain an annealed sheet; a cold rolling step after intermediate annealing, in which the annealed sheet is cold rolled at a rolling reduction of 20% or more.

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