JP6580332B2 - Aluminum alloy foil, current collector for battery electrode, and method for producing aluminum alloy foil - Google Patents

Description

  The present invention relates to an aluminum alloy foil excellent in strength and elongation characteristics, a current collector for a battery electrode using the aluminum alloy foil, and a method for producing the aluminum alloy foil.

Aluminum alloy foil used for packaging materials for batteries such as lithium-ion secondary batteries is produced by unwinding a foil coil at the battery manufacturer, applying an active material to the foil surface, drying, and pressing the electrode to create an electrode. Yes. This electrode (positive electrode / negative electrode) is wound through a separator and stored in a battery case. At this time, if the strength or elongation of the foil is low, the risk of breakage at the time of electrode production or at the time of winding the electrode increases, so it is desirable that these two physical properties be as high as possible.
For example, in Patent Documents 1 to 3, a hard foil having high strength and elongation is obtained by adjusting the amount of Si and the amount of Fe.

JP 2014-88598 A JP 2014-109057 A JP 2014-205886 A

  However, the hard foil obtained by the conventional method is improved in elongation by increasing the final cold rolling rate, but the high elongation obtained in this way ensures high elongation immediately after rolling. Even if it can be done, it shows a change over time, with the growth gradually decreasing over the course of days. Therefore, when actually used by the user, the elongation has been reduced.

  The present invention has been made against the background of the above circumstances, and provides an aluminum alloy foil, a current collector for battery electrodes, and a method for producing an aluminum alloy foil that have excellent strength and elongation characteristics over time. Objective.

That is, among the aluminum alloy foils of the present invention, the first present invention is, in mass%, Fe: 0.7% to 1.5%, Si: 0.20 % to 0.5% , Cu: It contains 0.01% or more and 0.20% or less , and the balance is composed of Al and inevitable impurities, and when 60 days have elapsed from the completion of the final cold rolling, the tensile strength is 190 MPa or more and the elongation is It is characterized by being 5.0% or more.

The aluminum alloy foil of the second aspect of the present invention is, in mass%, Fe: 0.7% to 1.5%, Si: 0.15% to 0.5%, Cu: 0.01% to 0.00%. 20% or less , Mn: 0.05% or more and 0.3% or less, with the balance being composed of Al and inevitable impurities, and tensile strength at the time when 60 days have passed since the last cold rolling was completed Is 190 MPa or more and elongation is 5.0% or more .

A battery electrode current collector according to a third aspect of the present invention comprises the aluminum alloy foil according to the present invention.

The method for producing an aluminum alloy foil according to the fourth aspect of the present invention produces an aluminum alloy foil having a tensile strength of 190 MPa or more and an elongation of 5.0% or more when 60 days have elapsed from the completion of the final cold rolling. A method of homogenizing the aluminum alloy ingot having the composition of the present invention at 450 to 580 ° C. for 4 hours or more, and then performing a cold rolling with a final cold rolling rate of 98% or more. It is characterized by being.

  The composition and production conditions in the present invention will be described below. In addition, all the following component content is shown by the mass%.

Si: 0.15% to 0.5%
Si may be added to increase the strength of the foil, but its effect is smaller than that of Cu, Mn, and Mg, and adding too much increases the risk of generating Al-Fe-Si coarse crystals. . Coarse crystallized materials are not normally added positively because they lead to pinholes in the foil and breakage during rolling. However, it has been found that addition with a certain amount or more of Fe not only suppresses the decrease in elongation immediately after rolling but also improves it. If the Si content is less than 0.15%, the effect on elongation is small, and if it exceeds 0.5%, coarse crystals formed during casting cause pinholes, breakage during rolling, and a decrease in elongation. For this reason, Si content is defined to the said range. For the same reason, it is desirable that the lower limit of Si content is 0.2% and the upper limit is 0.35%.

Fe: 0.7% to 1.5%
Fe is an element that can improve the strength and elongation of the foil. Moreover, the fall of the elongation after rolling can be suppressed by adding with Si. When the Fe content is less than 0.7%, the elongation value is low, and even when added together with Si, the elongation after rolling is hardly improved. If the Fe content exceeds 1.5%, the Al-Fe-based and Al-Fe-Si-based crystals are coarsened, and pinholes, breakage during rolling, and elongation decrease occur. For this reason, Fe content is defined to the said range. For the same reason, it is desirable that the lower limit of the Fe content is 1.0% and the upper limit is 1.4%.

Cu: 0.01% to 0.20%
Cu is an element that can improve the strength of the foil, and is contained as desired. If the Cu content is less than 0.01%, the contribution to strength improvement is insufficient, and if it exceeds 0.20%, the strength becomes too high and rolling becomes difficult. In addition, a decrease in elongation occurs. For this reason, when Cu is contained if desired, the Cu content is set to the above range. For the same reason, it is desirable that the lower limit of the Cu content is 0.05% and the upper limit is 0.1%. Cu may be contained as an inevitable impurity in an amount of less than 0.01%.

Mn: 0.05% or more and 0.3% or less Mn is an element that improves the strength of the foil and also increases the elongation when used together with Fe, and is contained as desired. However, the high elongation when used together with Fe is obtained immediately after rolling, and the high elongation is suddenly lost due to a change with time. By using together with Fe and Si, it is possible to suppress a decrease in elongation due to aging, but when added over 0.3%, Al-Fe-Mn and Al-Fe-Mn-Si crystallization products Becomes coarse and causes pinholes, breakage during rolling, and decrease in elongation. For this reason, when it contains Mn, the content shall be 0.3% or less. In addition, in order to fully obtain the said effect | action, it is desirable to contain Mn 0.05% or more. Note that there is no problem even if Mn is contained as an inevitable impurity up to 0.02%.

When 60 days have passed since the last cold rolling was completed: Tensile strength is 190 MPa or more and elongation is 5.0% or more. There is a certain period from the manufacture of the foil to the actual use by the user. May be more than a day away. In particular, it has been confirmed that high elongation foils of Al-Fe and Al-Fe-Mn alloys decrease in elongation immediately after rolling, and have the mechanical properties expected when used by users. There is no possibility. In the present invention, when 60 days have elapsed from the completion of the final cold rolling, the tensile strength is 190 MPa or more and the elongation is 5.0% or more, so that sufficient characteristics can be obtained in the change over time.

Homogenization treatment: 450 to 580 ° C., 4 hours or longer If the homogenization treatment is omitted, the amount of Fe solid solution in the Al matrix does not decrease, so that the improvement in elongation immediately after the final rolling becomes dull.
Further, when the homogenization temperature is less than 450 ° C. or the homogenization time is less than 4 hours, the decrease in the amount of solid solution of Fe is insufficient and the effect of improving the elongation is not sufficiently exhibited. Similarly, even if the homogenization temperature exceeds 580 ° C., the decrease in the amount of Fe solid solution is insufficient, and there is a possibility that the ductility of the foil accompanying the generation of coarse precipitates may be reduced.

Final cold rolling rate of 98% or more By setting the final cold rolling to 98% or more, the strength and elongation of the foil can be improved. If it is less than 98%, the effect of improving the elongation is particularly low. In addition, although an upper limit is not prescribed | regulated in particular, even if it exceeds 99.9%, the improvement of intensity | strength and elongation will be saturated.
The final cold rolling is indicated by the rolling rate after the final intermediate annealing when intermediate annealing is performed during the cold rolling, and is indicated by the rolling rate after the start of cold rolling when the intermediate annealing is not performed.

  That is, according to the present invention, it is possible to maintain an excellent strength and elongation characteristic over time, and in part, there is an effect that an aluminum alloy foil whose elongation characteristic improves over time can be obtained.

Hereinafter, an embodiment of the present invention will be described.
The aluminum alloy used as the material of the aluminum alloy foil contains Fe: 0.7% or more and 1.5% or less, Si: 0.15% or more and 0.5% or less, which is the component range of the present invention. Cu: 0.01% or more and 0.20% or less, Mn: 0.05% or more and 0.3% or less is contained so that a composition comprising Al and inevitable impurities can be obtained. . The melting method is not particularly limited, and a known semi-continuous casting method or the like can be used.
The obtained ingot is subjected to a homogenization treatment of holding at 450 to 580 ° C. for 4 hours or more, and then subjected to hot rolling.
Then, it cold-rolls and it is set as the aluminum alloy foil whose final thickness is 10-20 micrometers, for example. During the cold rolling, intermediate annealing can be performed once or twice or more. There are two types of intermediate annealing: batch annealing in which a coil is put in a furnace and held for a certain period of time, and a material is rapidly heated and cooled by a continuous annealing line (hereinafter referred to as CAL annealing). In the present invention, any method may be used, but the CAL annealing improves the strength of the foil as the final material due to the refinement of crystal grains and the increase in the amount of solute elements dissolved by rapid heating and quenching.
The conditions for batch annealing are, for example, 350 to 450 ° C. and 3 hours or more. If the temperature is less than 350 ° C. or less than 3 hours, recrystallization may not be completed, and if the temperature exceeds 450 ° C., there is a risk of coarsening of crystal grains due to secondary recrystallization. CAL annealing may be performed under conditions of a temperature rising rate: 10 to 250 ° C./second, a heating temperature: 400 ° C. to 550 ° C., a holding time: none to 5 seconds, and a cooling rate: 20 to 200 ° C./second.
In the present invention, intermediate annealing may not be performed.
In cold rolling, the final cold rolling rate is 98% or more. A final cold rolling rate is shown by the rolling rate after the last intermediate annealing, when performing intermediate annealing. Moreover, when not performing intermediate annealing, it showed with the rolling rate after the cold rolling start.

The aluminum alloy foil of the present invention has the characteristics that the tensile strength is 190 MPa or more and the elongation is 5.0% or more when 60 days have passed since the completion of the final cold rolling.
Moreover, the aluminum alloy foil of the present invention can be used for a secondary battery electrode current collector, and can be particularly suitably used for a lithium ion secondary battery. The electrode current collector can be used for both the positive electrode and the negative electrode, but is mainly used for the positive electrode.

Ingots of aluminum alloys having the respective compositions shown in Table 1 (the balance Al and other inevitable impurities) were homogenized and subjected to homogenization at 550 ° C. for 4 hours. Each material was made into a 4.5 mm plate by hot rolling at a finishing temperature of 260 ° C. Thereafter, cold rolling was performed to 2.5 mm, intermediate annealing was performed except for some materials, and a final cold rolling was performed to prepare a sample of an aluminum alloy foil having a thickness of 12 μm and a width of 1200 mm.
Intermediate annealing was performed in Example No. No. 11 was performed using a continuous annealing line (CAL). The CAL conditions were: temperature rising rate: 70 ° C./second, heating temperature: 500 ° C., holding time: 4 seconds, cooling rate: 50 / second. Example No. No. 11 was performed in a batch furnace at a heating temperature of 360 ° C. and a holding time of 4 hours, the heating rate was 50 ° C./hour, and the cooling was air cooling.
In Example 8 and Comparative Example 12, the rolling rate was varied by setting the intermediate annealing plate thickness to 0.7 mm and 0.4 mm, respectively. The rolling ratio of each material is shown in Table 1.

(Tensile strength, elongation)
The strength and elongation of each specimen were measured over time (immediately after rolling, 14 days and 60 days after the final cold rolling).
Tensile strength and elongation were measured in accordance with JIS Z2241 by taking a JIS No. 5 test piece from a sample and measuring it with a universal tensile tester (manufactured by Shimadzu Corporation) at a pulling speed of 2 mm / min. The calculation of the elongation rate is as follows. First, before the test, two lines are marked at the center of the test piece in the vertical direction of the test piece at an interval of 50 mm as a gauge distance. After testing, the fracture surface of the aluminum alloy foil was put together to measure the distance between marks, and the elongation (mm) obtained by subtracting the gauge distance (50 mm) from that was divided by the distance between gauge points (50 mm). (%) Was calculated. The measurement results are shown in Table 2.

(Rollability)
Rollability is a wide rolling with a width exceeding 1200 mm, when the final pass (rolling rate) was able to be rolled without breaking, and when the final pass was broken 3 times or less per coil (about 10,000 m) △ was marked as x for those judged to be difficult to continue rolling for reasons such as breaking more than 3 times or being too hard. ○ is preferable, but if it is Δ or more (with a final pass of about 10000 m within 3 breaks), there is no problem in production.

Claims (4)

Fe: 0.7% or more and 1.5% or less, Si: 0.20 % or more and 0.5% or less , Cu: 0.01% or more and 0.20% or less , with the balance being Al. An aluminum alloy foil having a composition composed of inevitable impurities and having a tensile strength of 190 MPa or more and an elongation of 5.0% or more after 60 days from the completion of the final cold rolling. In mass%, Fe: 0.7% to 1.5%, Si: 0.15% to 0.5%, Cu: 0.01% to 0.20% , Mn: 0.05% or more It has a composition comprising 0.3% or less , the balance being Al and inevitable impurities, and when 60 days have elapsed from the completion of the final cold rolling, the tensile strength is 190 MPa or more and the elongation is 5.0% or more. The aluminum alloy foil characterized by being . Battery electrode current collector, characterized in that an aluminum alloy foil according to claim 1 or 2. 3. A method for producing an aluminum alloy foil having a tensile strength of 190 MPa or more and an elongation of 5.0% or more after 60 days from the completion of the final cold rolling, wherein the composition according to claim 1 or 2. An aluminum alloy ingot having a final cold rolling rate of 98% or more at the time of cold rolling. Manufacturing method.