JP6280738B2 - Aluminum alloy for hard foil, aluminum alloy hard foil, aluminum alloy foil for positive electrode current collector of lithium ion secondary battery, and method for producing aluminum alloy hard foil - Google Patents

Description

  The present invention relates to an aluminum alloy for hard foil, an aluminum alloy hard foil, an aluminum alloy foil for a positive electrode current collector of a lithium ion secondary battery, and a method for producing the aluminum alloy hard foil.

  In recent years, secondary batteries such as lithium ion secondary batteries have been used as power sources for mobile electronic devices such as mobile phones and notebook computers. In addition, the use of lithium ion secondary batteries for in-vehicle batteries of eco-cars such as hybrids and electric cars has been expanded. The electrode material of the lithium ion battery includes a positive electrode plate, a separator, and a negative electrode plate. The positive electrode plate is a step of applying an active material having a size of about 100 μm on both sides to a current collector aluminum foil having a thickness of about 15 to 30 μm together with a solvent, a drying step for removing the applied solvent, Manufactured through a crimping process for increasing the density of the active material. The positive electrode plate manufactured in this way is wound in a spiral shape via a negative electrode plate and a separator, and then housed in a metal case and sealed to form a battery. At present, JIS A1085 and JIS A3003 aluminum materials are generally used for the aluminum foils for the above applications.

Recently, in order to extend the usage time of mobile electronic devices and increase the travel distance of electric vehicles, it has been strongly desired to increase the battery capacity, that is, to increase the energy density of the battery. Therefore, it has been attempted to produce a higher-density electrode material by increasing the load compared to the conventional case when the positive electrode plate is pressure-bonded.
From such a viewpoint, an aluminum alloy hard foil having high strength and elongation has been proposed (see Patent Documents 1 and 2).

JP 2009-064560 A JP 2011-179062 A

  However, when manufacturing a thin foil of an aluminum alloy, the rollability is inhibited as the material strength increases. In order to avoid this, it is necessary to cope by performing intermediate annealing a plurality of times or increasing the number of rolling passes, and as a result, productivity is lowered. In order to avoid a decrease in productivity, it is necessary to reduce the material strength, and there is a problem that it is not suitable as a high strength aluminum alloy hard foil.

Usually, in aluminum alloys, tensile strength increases linearly as strain is introduced, but it is known that there is a phenomenon in which tensile strength does not increase or decreases under specific alloy components or specific deformation conditions, This phenomenon is called process softening.
However, since work softening has occurred only under specific conditions, it has not been applied to industrially used alloy components or manufacturing processes.
The present invention has been made against the background of the above circumstances, and it is possible to express work softening in the middle of the process by regulating the alloy components, and to produce thin foils and wide high-strength aluminum alloy hard foils. The basic purpose is to provide without reducing

  That is, the 1st present invention among the aluminum alloys for hard foils of the present invention is mass%, contains Fe: 1.00-1.70%, Mn: 0.10-0.50%, and the remainder is It consists of Al and inevitable impurities, and the total amount of Cu, Mg, Cr and Zr has a composition of 0.05% or less, and the total amount of Fe and Mn in the composition is 2.0% or less. To do.

  The aluminum alloy for hard foil of the second aspect of the present invention is characterized in that, in the first aspect of the present invention, the Fe / Mn ratio in the composition is 3.5 or more.

  The aluminum alloy hard foil of the third invention has the composition described in the first or second invention, the foil thickness is 5 to 20 μm, the tensile strength is 200 MPa or more, and the elongation is 3.0%. It is the above.

  The aluminum alloy hard foil of the fourth aspect of the present invention is characterized in that, in the third aspect of the present invention, the elongation before the final cold rolling is 2.0% or more.

  An aluminum alloy foil for a positive electrode current collector of a lithium ion secondary battery according to a fifth aspect of the present invention comprises the aluminum alloy hard foil according to the third or fourth aspect.

  A method for producing an aluminum alloy hard foil according to a sixth aspect of the present invention comprises hot rolling, cold rolling, or finishing with a finishing temperature of 200 to 290 ° C. on an aluminum alloy having the composition described in the first or second aspect of the present invention. When the final cold rolling is performed and the rolling reduction from hot rolling to after the final cold rolling is performed, when the intermediate annealing is performed during the cold rolling, the rolling reduction from the intermediate annealing to after the final cold rolling is set to 90.0. It is characterized by obtaining a foil having a thickness of 5 to 20 μm by ˜99.9%.

  Below, the conditions prescribed | regulated by this invention and the reason are demonstrated. In addition, each content in a composition is shown by the mass%.

  The aluminum alloy for hard foils of the present invention can have high tensile strength and elongation characteristics by using appropriate alloy components. This will be described below.

Fe: 1.00 to 1.70%
Fe secures tensile strength and elongation, and causes work softening during production. However, if the Fe content is less than 1.00%, the tensile strength and the elongation decrease. Moreover, processing softening does not express. On the other hand, if it exceeds 1.70%, the strength is improved and the thin foil, particularly the rollability of 15 μm or less, which is a particularly suitable foil thickness, is inhibited. For this reason, Fe content is set to 1.00-1.70%. For the same reason, the upper limit is preferably 1.35%.

Mn: 0.10 to 0.50%
Mn ensures tensile strength and is added together with Fe to cause work softening during production. However, if the Mn content is less than 0.10%, the tensile strength is insufficient. Moreover, processing softening does not express. On the other hand, if the Mn content exceeds 0.50%, a giant crystallized product is generated and breaks during rolling. For this reason, the Mn content is limited to 0.10% to 0.50%. For the same reason, it is desirable to set the upper limit to 0.30%.

Cu / Mg / Cr / Zr: 0.05% or less in total amount When Cu, Mg, Cr, Zr exceeds 0.05% in total amount, solid solution hardening occurs and work softening does not occur, and thin foil In order to obtain this, productivity decreases. For the same reason, the total amount is preferably 0.02% or less.

Fe + Mn: 2.0% or less When the total amount of Fe and Mn exceeds 2.0%, an Al—Fe—Mn-based giant crystallized product is generated in an ingot produced by semi-continuous casting. It may break during rolling as a starting point. For this reason, the total amount of Fe and Mn is 2.0% or less. In addition, it is desirable to set it as 1.9% or less for the same reason.

Fe / Mn ratio: 3.5 or more When the Fe / Mn ratio is less than 3.5, work softening is hardly exhibited. Further, the rollability of 15 μm or less, which is a thin foil, particularly a suitable foil thickness, is inhibited. For this reason, the Fe / Mn ratio is desirably 3.5 or more. For the same reason, the Fe / Mn ratio is more preferably 5.0 or more. Moreover, since it becomes difficult to express work softening even if there is little Mn, it is desirable that Fe / Mn ratio shall be 8.0 or less.

Tensile strength: 200 MPa or more Load resistance is required when unwinding the foil during processing, and breakage during rolling is prevented. Moreover, when using as an aluminum alloy foil for lithium ion secondary battery positive electrode electrical power collectors, intensity | strength is required so that a fracture | rupture does not arise when crimping an active material and manufacturing a positive electrode plate. For these reasons, a tensile strength of 200 MPa or more is required.

Elongation: 3.0% or more If the elongation is low, it tends to break and rolling of the thin foil becomes difficult. Further, when used as an aluminum alloy foil for a positive electrode current collector of a lithium ion secondary battery, breakage due to bending is unlikely to occur, and the electrode material can be bent to improve usability. For this reason, it is desirable that the lower limit of elongation be 3.0%. For the same reason, it is more desirable to set the lower limit of elongation to 4.0%.

Elongation before final cold rolling: 2.0% or more If the elongation before final cold rolling, which corresponds to the last pass of cold rolling, is low, it is easy to break during final cold rolling, and thin foil rolling becomes difficult. For this reason, it is desirable that the lower limit of the elongation before the final cold rolling is 2.0%. For the same reason, it is more desirable to set the lower limit of elongation before the final cold rolling to 4.0%.

  Moreover, the aluminum alloy hard foil of the present invention can be obtained as a foil having a thickness of 5 to 20 μm through final cold rolling, which is the last pass of hot rolling, cold rolling, and cold rolling. Below, the prescription | regulation in a manufacturing process is demonstrated.

Hot rolling finish temperature: 200 ° C. or more and 290 ° C. or less When the finish temperature during hot rolling is less than 200 ° C., stable rolling becomes difficult due to low temperature. On the other hand, when the finishing temperature exceeds 290 ° C., the temperature becomes high and partial recrystallization occurs, resulting in insufficient elongation. For this reason, it is desirable that the hot rolling finish temperature be 200 to 290 ° C. For the same reason, it is more desirable that the lower limit of the finishing temperature is 240 ° C. and the upper limit is 280 ° C.

Reduction ratio: 90.0 to 99.9%
By appropriately setting the rolling reduction, the number of intermediate annealing can be reduced, and a high-strength aluminum alloy hard foil can be manufactured with high productivity. When the rolling reduction is less than 90.0%, the number of intermediate annealing increases and productivity is lowered. Moreover, processing softening does not express. On the other hand, if the rolling reduction exceeds 99.9%, the required number of cold rolling increases and productivity decreases. Moreover, the improvement of the tensile strength can hardly be expected, and surface cracks are easily generated and easily broken. For this reason, it is desirable that the rolling reduction is 90.0 to 99.9%. For the same reason, the lower limit of the rolling reduction is more preferably 98.0%, and the upper limit is more preferably 99.7%.

Foil thickness: 5-20 μm
When the foil thickness is less than 5 μm, the load resistance at the time of unwinding in the processing of the foil is insufficient, and the production of the foil becomes difficult. Moreover, the handling at the time of processing foil is difficult. On the other hand, when it exceeds 20 μm, it is difficult to obtain the merit of the thin foil. Moreover, in order to ensure the battery capacity at the time of using for the positive electrode electrical power collector for lithium ion secondary batteries, 20 micrometers or less are desirable. For this reason, the foil thickness is desirably 5 to 20 μm. For the same reason, it is more desirable that the foil thickness has a lower limit of 6 μm and an upper limit of 15 μm.

  As described above, according to the present invention, it is possible to efficiently produce a thin foil and a wide aluminum alloy hard foil using work softening at the time of manufacture, and the aluminum alloy hard foil has high tensile strength and high strength. It has elongation characteristics.

It is a graph which shows the work hardening curve in an Example.

Hereinafter, an embodiment of the present invention will be described.
The aluminum alloy having the composition of the present invention can be melted by a conventional method, and a known semi-continuous casting method or continuous casting rolling method can be employed.
The ingot obtained by semi-continuous casting can be homogenized if desired. When performing the homogenization treatment, it is desirable to control the homogenization temperature to 420 to 620 ° C and the holding time to 1 to 12 hours. Thereby, the precipitation state of Fe and Mn can be made into a suitable state by rolling of thin foil.
If the homogenous temperature is less than 420 ° C., Mn does not precipitate, so that rolling becomes difficult due to work hardening. On the other hand, when the homogeneous temperature exceeds 620 ° C., local dissolution may occur. For this reason, the homogeneous temperature is desirably 420 to 620 ° C. When the homogenization time is less than 1 hour, Mn does not precipitate, so that rolling becomes difficult due to work hardening. On the other hand, if it exceeds 12 hours, the precipitates are enlarged and easily broken during rolling. For this reason, it is desirable that the homogeneous time is 1 to 12 hours.

Thereafter, hot rolling is performed to obtain an aluminum alloy material. Although hot rolling can be performed by a conventional method, the finishing temperature is desirably 200 to 290 ° C, and more desirably 240 to 280 ° C.
The aluminum alloy material is subjected to cold rolling, subjected to intermediate annealing, and cold rolling and final cold rolling are performed again. The intermediate annealing can be performed by a conventional method using a batch annealing furnace or a continuous annealing furnace.
The number of intermediate annealing is not particularly limited, and can be performed once or twice or more. However, in this embodiment, work softening is brought about at the time of manufacture, and the rolling reduction can be set large, so that the number of intermediate annealings can be reduced.
In the present embodiment, intermediate annealing may not be performed.

The rolling reduction is desirably 90.0 to 99.9%, and more desirably 98.0 to 99.7%.
An aluminum alloy hard foil having a thickness of 5 to 20 μm can be obtained through cold rolling and final cold rolling. The aluminum alloy hard foil has a tensile strength of 200 MPa or more. Further, the elongation is 3.0% or more, and more preferably 4.0% or more.
The rolling reduction refers to the sheet thickness reduction rate, and is expressed as a percentage of (T0−T1) / T0, where T0 is the initial sheet thickness and T1 is the sheet thickness after rolling.

  Although the obtained aluminum alloy hard foil can be used for various applications, it can be suitably used as an electrode material for a lithium ion secondary battery as an aluminum alloy foil for a positive electrode current collector of a lithium ion secondary battery.

Examples of the present invention will be described below in comparison with comparative examples.
An ingot of aluminum alloy having various compositions shown in Table 1 (the balance Al and other inevitable impurities) was cast into a 500 mm thick ingot by semi-continuous casting. The obtained ingot was homogenized at a homogeneous temperature of 580 ° C. and a holding time of 10 hours, and then chamfered to remove the non-uniform layer on the surface.
Thereafter, the cooled ingot was reheated to 520 ° C., and was subjected to hot rolling at a finishing temperature shown in Table 2 to obtain a plate material having a thickness of 3.0 mm.

Next, it is subjected to cold rolling, and during the cold rolling, intermediate annealing is performed at 350 ° C. for 3 hours in a batch annealing furnace or at 500 ° C. for 10 seconds using a continuous annealing furnace, and the rolling reduction shown in Table 2 is performed. Then, cold rolling and final cold rolling as the last pass of the cold rolling were performed again so that the foil thickness was 12 μm and the width was 1400 mm to obtain an aluminum alloy hard foil.
The following evaluation was performed using the produced aluminum alloy hard foil as a test material.

  Of the samples prepared by the above process, “○” indicates that the sample was prepared without breaking, and “△” indicates that the sample was not rolled but has a low rolling property. Samples that could not be obtained were evaluated as “x”, and the evaluation results of rollability are shown in Table 2.

  No. 5 test piece based on JIS Z2241 was produced from the aluminum alloy hard foil produced above, and the tensile strength, the elongation and the elongation before the final cold rolling were measured. The measurement results are shown in Table 2.

  Samples prepared in the above process are subjected to the above tensile tests in each cold rolling process. Samples that do not increase or decrease the tensile strength are processed softened “Yes”, samples that continue to increase tensile strength are processed softened “No” The results are shown in Table 2.

  As a result of the test, this example can efficiently produce a thin foil and a wide aluminum alloy hard foil without impairing the rollability due to the occurrence of work softening. The aluminum alloy hard foil had excellent properties in both tensile strength and elongation.

  Comparative Example No. In Examples 3 and 6, rolling was impossible due to breakage, and the other comparative examples were inferior in any of the above characteristics.

  In order to specifically show the expression of work softening, the tensile strength was measured in each step of cold rolling for Example 2 and Comparative Example 7. The results are shown in FIG. In the examples, work softening clearly occurred, whereas in the comparative example, work softening did not occur and work hardening continued.

Claims (6)

  In mass%, Fe: 1.00 to 1.70%, Mn: 0.10 to 0.50%, the balance is made of Al and inevitable impurities, and the total amount of Cu, Mg, Cr and Zr is 0. An aluminum alloy for hard foils having a composition of 0.05% or less and a total amount of Fe and Mn in the composition of 2.0% or less.   The aluminum alloy for hard foil according to claim 1, wherein the Fe / Mn ratio in the composition is 3.5 or more.   An aluminum alloy hard foil having the composition according to claim 1, having a foil thickness of 5 to 20 μm, a tensile strength of 200 MPa or more, and an elongation of 3.0% or more.   The aluminum alloy hard foil according to claim 3, wherein an elongation before final cold rolling is 2.0% or more.   An aluminum alloy foil for a positive electrode current collector of a lithium ion secondary battery, comprising the aluminum alloy hard foil according to claim 3. The aluminum alloy having the composition according to claim 1 or 2 is subjected to hot rolling, cold rolling, and final cold rolling at a finishing temperature of 200 to 290 ° C, from hot rolling to after final cold rolling. Reduction ratio, when performing intermediate annealing during cold rolling, obtain a foil with a thickness of 5 to 20 μm by setting the reduction ratio from after intermediate annealing to after final cold rolling to 90.0 to 99.9%. The manufacturing method of the aluminum alloy hard foil characterized by these.

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