JP2013241663A - Rolled copper foil for collector of secondary battery and method for producing the same - Google Patents

Abstract

The present invention provides a secondary battery having a high 0.2% proof stress and electrical conductivity in the vertical direction of rolling, and a high 0.2% proof stress even after heat treatment at 350 ° C. for 1 hour. It is an object to provide a rolled copper foil for a secondary battery current collector that can improve the electrical characteristics of the secondary battery.
A rolled copper foil containing at least one of Cr, Zr, and Ti in a total amount of 0.01 to 0.6 mass%, with the balance being copper and inevitable impurities, and deviation from a (111) plane Is a rolled copper foil for a secondary battery current collector, in which the area ratio of the region in which the crystal plane within 15 degrees is oriented in the vertical direction of rolling is higher than 45%.
[Selection] Figure 1

Description

  The present invention relates to a rolled copper foil applicable to a current collector for a secondary battery and a method for producing the same, and particularly relates to a rolled copper foil having a high 0.2% yield strength and a method for producing the same.

The rolled copper foil is used for a negative electrode current collector of a secondary battery such as a lithium ion battery. The rolled copper foil holds a negative electrode active material thereon and is used as a negative electrode current collector.
With the recent demand for increasing battery capacity, changes in the negative electrode active material from carbon-based to silicon (Si) -based or tin (Sn) -based are being studied. Although these new active materials have a large charge / discharge capacity, they have a feature that the volume expansion / contraction due to charge / discharge is larger than that of carbon. Along with this deformation of the active material, if the rolled copper foil of the negative electrode current collector is deformed beyond its elastic limit, the negative electrode is deformed, the current collector is broken, the active material is dropped, and the battery capacity is reduced. Cause. Therefore, there is a need for a rolled copper foil for a negative electrode current collector having a high 0.2% yield strength. In particular, since the rolling width direction in the rolled copper foil manufacturing process is the longitudinal direction of the negative electrode, high strength is required.

As described above, if the 0.2% proof stress of the rolled copper foil for a battery is low, the performance of the battery is deteriorated. Therefore, it is required to increase the 0.2% proof stress. Further, the rolled copper foil for a battery is required to have 0.2% proof stress and high conductivity.
In the battery assembly process, heat treatment at 300 to 350 ° C. is performed to imidize polyimide used for fixing the active material. When used for batteries, it is required that the rolled copper foil is not softened even by this heat treatment.

Several proposals have been made to increase the strength of the rolled copper foil. The invention disclosed in Patent Document 1 contains 1.5 to 3.0 wt% of Ag, and is combined with Cr or Zr. The strength is increased by precipitation. A high strength of 640 MPa or higher is obtained with a 0.2% yield strength in the rolling parallel direction. However, since Ag is expensive and has a small reserve, it is not suitable as a high-concentration additive element for general-purpose materials.
In the invention disclosed in Patent Document 2, Fe is added at a high concentration to be two-phased to increase the strength. A high strength of 779 MPa or more is obtained with a 0.2% yield strength in the rolling parallel direction. However, the conductivity is as low as 56% IACS or less.
In the invention disclosed in Patent Document 3, the precipitation state is controlled by a Cu—Cr—Zr alloy to achieve both tensile strength and conductivity. However, the tensile strength is approximately 600 MPa or less and is low.

JP 2008-081835 A JP 2009-242871 A JP 2006-283106 A

For the use of a battery current collector, it is important that the 0.2% yield strength in the vertical direction of rolling is high and the conductivity is high, and such a rolled copper foil is not known.
The present invention has a high 0.2% proof stress and electrical conductivity in the vertical direction of rolling, and maintains a high 0.2% proof stress even after heat treatment for 1 hour at a temperature of 350 ° C. or lower. It is an object of the present invention to provide a rolled copper foil for a secondary battery current collector and a method for producing the same, which can improve the electrical characteristics of the secondary battery.

There are four known mechanisms for strengthening a metal material: dispersion strengthening, solid solution strengthening, dislocation strengthening, and grain boundary strengthening (see, for example, Reference 1). In order to positively use dispersion strengthening or solid solution strengthening, it is necessary to increase the amount of added elements. In this case, however, the conductivity is lowered, and therefore, the application is limited to the usage of the current collector. Regarding dislocation strengthening and grain boundary strengthening, rolled copper foil is generally manufactured by a high rolling process with a processing rate of 80% or more, and is a strengthening mechanism that has already been used.
In the present invention, it has been found that the orientation enhancement is manifested as a strengthening mechanism different from the above four mechanisms. This is a technique for increasing the yield strength by accumulating crystal planes in which crystal slip hardly occurs in the stress direction. According to this method, since the electrical conductivity is not lowered unlike the dispersion strengthening and the solid solution strengthening, it can contribute to the improvement of characteristics of the rolled copper foil for current collector.

(Reference 1)
Koda Naruyasu, "Standard Metal Engineering Course Vol.9 Introduction to Metal Physics", Corona, 1964 (Reference 2)
Kunio Ito, “Light metal” “Aggregate structure of aluminum alloy plate”, Light Metal Society, Vol. 43, No. 5, 1993, p285-293

That is, the problem of the rolled copper foil for the secondary battery current collector described above has been solved by the following invention.
(1) A rolled copper foil containing 0.01 to 0.6 mass% in total of at least one of Cr, Zr and Ti, with the balance being made of copper and inevitable impurities, and deviation from the (111) plane A rolled copper foil for a secondary battery current collector, wherein an area ratio of a region in which a crystal plane within 15 degrees is oriented in a vertical direction of rolling is higher than 45%.
(2) Containing at least one of Cr, Zr and Ti in a total amount of 0.01 to 0.6 mass%, and further adding at least one of Sn, Zn, Mn, Mg and Ag in a total of 0.01 to 0 .95 mass% contained, the balance is a rolled copper foil made of copper and unavoidable impurities, and the area ratio of the region in which the crystal plane with a deviation from the (111) plane of 15 degrees or less is oriented in the rolling vertical direction is more than 45% High rolled copper foil for secondary battery current collector.
(3) After the heat treatment held at 350 ° C. for 1 hour, the area ratio of the region in which the crystal plane whose deviation from the (111) plane is within 15 degrees is oriented in the vertical direction of rolling is higher than 45% (1) Or the rolled copper foil for secondary battery collectors as described in (2).
(4) An ingot obtained by melting (step 1) and casting (step 2) a copper alloy having the alloy composition of the rolled copper foil for a secondary battery current collector according to (1) or (2) Furthermore, homogenization heat treatment (step 3) for 5 minutes to 4 hours at 900 to 1030 ° C., high temperature rolling 1 (step 4) and high temperature rolling 2 (step 5) at a processing rate of 40 to 95% at a temperature of 600 to 1030 ° C. , Cooling (step 6), chamfering (step 7), intermediate cold rolling (step 8) and heat treatment (step 9) with a processing rate of 90.0 to 99.9%, and processing rate of 66 to A method of manufacturing a rolled copper foil for a secondary battery current collector that is subjected to 95% final cold rolling (step 10), wherein the high temperature rolling 2 (step 5) has a processing temperature of 400 ° C. or higher and 600 ° C. or lower. The rate is 50% to 70%, and the heat treatment (step 9) is 40%. Held at 0.5 to 450 ° C. for 0.5 to 3 hours, or the high temperature rolling 2 (step 5) is performed at a processing temperature of 400 to 600 ° C. and a processing rate of 20 to 40%. Step 9) is a method for producing a rolled copper foil for a secondary battery current collector that is held at 450 ° C. or higher and 500 ° C. or lower for 0.5 to 3 hours.
(5) Low temperature annealing is performed after the said last cold rolling (step 10), The manufacturing method of the rolled copper foil for secondary battery collectors as described in (4) characterized by the above-mentioned.

  According to the present invention, when the rolled copper foil as the current collector is deformed as the active material such as Sn-based or Si-based, which has a large expansion / contraction amount during charge / discharge, is deformed, the current collecting is performed. Since the deformation of the body is within the elastic deformation region, the current collector can follow the shape change of the active material. Therefore, the active material can be prevented from being detached from the current collector, and the charge / discharge cycle characteristics of the secondary battery can be improved.

It is the figure which showed an example of the crystal orientation of the copper alloy of the case where (a) and the case where it does not orient (b) when the crystal plane in which the shift | offset | difference from a (111) crystal plane is 15 degrees or less in the rolling perpendicular direction in this invention is oriented . It is a figure explaining SB direction and Brass direction. 10 is a drawing-substituting photograph showing a transmission electron microscope image of Example 104 after holding at 350 ° C. for 1 hour. The arrows in the figure indicate fine precipitated particles of Cr. It is the flowchart which showed the manufacturing process of the rolled copper foil of this embodiment. It is the figure which showed the softening curve by 1 hour isothermal heat processing about Example 104 and the comparative example 204. FIG. It is the figure which showed the stress-strain curve of the example 104 of this invention. 6 is a diagram showing a stress-strain curve of Comparative Example 301. FIG.

[Crystal orientation]
The crystal orientation display method in this specification takes a rectangular coordinate system in which the rolling direction (RD) of the material is the X axis, the rolling vertical direction (TD) is the Y axis, and the rolling surface normal direction (ND) is the Z axis. By using the index (hkl) of the crystal plane in which each region in the material is perpendicular to the Z axis (parallel to the rolling surface) and the index [uvw] of the crystal direction parallel to the X axis, (hkl) [uvw] In the form of In addition, parentheses representing families are used for equivalent orientations under the symmetry of the copper alloy cubic crystal, such as (132) [6-43] and (231) [3-46]. , {Hkl} <uvw>.

  The Brass orientation is a state in which the (110) plane faces the rolling surface normal direction (ND) and the (112) plane faces the rolling direction (RD), and is indicated by an index of {110} <112>. Similarly, the SB orientation is indicated by an index of {186} <211>.

  An example of the crystal orientation for orienting the (111) crystal plane in the vertical direction of rolling is shown in FIG. Further, FIG. 2 shows the azimuth relationship between the SB orientation and the Brass orientation introduced in Reference Document 2. A state in which the ratio of the texture alloy component including these crystal orientation components whose (111) plane faces TD is comprehensively suppressed is a texture having a predetermined area ratio defined in the present invention. Conventionally, a rolled copper foil in which the area ratios of atomic planes having these orientations are simultaneously controlled has not been known. In particular, in the rolled foil, the influence in the vicinity of the surface layer that undergoes additional shear deformation is strong, which is different from a normal rolled sheet.

[Crystal orientation analysis]
The FE-SEM / EBSD method is used for the analysis of the crystal orientation in the present embodiment. EBSD is an abbreviation for Electron Back Scatter Diffraction (Electron Backscatter Diffraction). Reflected Electron Kikuchi Line Diffraction (Kikuchi pattern) generated when a sample is irradiated with an electron beam in a Scanning Electron Microscope (SEM). This is the crystal orientation analysis technology used. Since the FE-SEM uses a field emission electron gun, the electron beam is thin and has a high spatial resolution. When the material is strongly distorted by rolling at a high processing rate like a rolled copper foil, it has a high orientation gradient in the structure. On the other hand, when a tungsten filament electron gun or the like having a large irradiation electron beam diameter is used, a diffraction pattern with a plurality of directions is formed, and it may be difficult to specify the direction.

  In this embodiment, the measurement of the area ratio of the region where the crystal plane whose deviation from the (111) plane is 15 degrees or less is oriented in the rolling vertical direction (TD) is 0.05 μm for a sample area of 700 μm or more. This is based on the result of scanning and analyzing the crystal orientation. That is, the area ratio is an area ratio in an arbitrary region of 700 square μm or more of the material. The measurement area is based on the inclusion of 200 or more crystal grains. If the measurement area is not sufficient, it is preferable to observe 2 to 5 fields of view and average them. In this specification, unless otherwise specified, the area ratio of a crystal plane having a certain crystal orientation is referred to as measured in this way.

  The information obtained in the azimuth analysis by EBSD includes azimuth information up to a depth of several tens of nanometers at which the electron beam penetrates the sample, but is sufficiently shallow with respect to the area being measured. It was described as an area ratio.

[Alloy components]
A preferred embodiment of the rolled copper foil for a secondary battery current collector of the present invention will be described below.
The rolled copper foil for a secondary battery current collector of the present invention contains at least one of Cr, Zr and Ti in a total amount of 0.01 to 0.6 mass%, and the balance is made of copper and inevitable impurities. And the area ratio of the area | region where the crystal plane within 15 degrees of deviations from the (111) plane is oriented in the rolling vertical direction is higher than 45%.
More preferably, at least one of Cr, Zr, and Ti is contained in a total of 0.01 to 0.35 mass%. Particularly preferably, the total content of at least one of Cr, Zr and Ti is 0.01 to 0.25 mass%.

The rolled copper foil for a secondary battery current collector of the present invention contains 0.01 to 0.6 mass% in total of at least one of Cr, Zr and Ti, and further contains Sn, Zn, Mn, A rolled copper foil containing at least one of Mg and Ag in a total amount of 0.01 to 0.95 mass%, the balance being copper and inevitable impurities, and a deviation from the (111) plane within 15 degrees The area ratio of the region where the surface is oriented in the vertical direction of rolling is higher than 45%. More preferably, it is higher than 50%, More preferably, it is higher than 55%. The upper limit of the area ratio is not limited but is 80% or less. If the area ratio is too small, the 0.2% yield strength in the vertical direction of rolling becomes too small.
More preferably, at least one of Cr, Zr, and Ti is contained in a total of 0.01 to 0.35 mass%. Particularly preferably, the total content of at least one of Cr, Zr and Ti is 0.01 to 0.25 mass%.
More preferably, a total of 0.01 to 0.48 mass% of at least one of Sn, Zn, Mn, Mg, and Ag is contained. Particularly preferably, 0.01 to 0.19 mass% in total of at least one of Sn, Zn, Mn, Mg, and Ag is contained.

  Further, the rolled copper foil for the secondary battery current collector described above is subjected to a heat treatment held at 350 ° C. for 1 hour, and the crystal plane whose deviation from the (111) plane is within 15 degrees is oriented in the vertical direction of rolling. It is preferable that the area ratio of the area | region to perform is higher than 45%.

The rolled copper foil for a secondary battery current collector of the present invention contains 0.01 to 0.6 mass% in total of at least one of Cr, Zr and Ti. This has the effect of improving the heat resistance without greatly reducing the conductivity.
One of the mechanisms is to disperse as fine particles that pin the movement of grain boundaries. As shown in FIG. 3, the grain boundary where Cr particles having a size of 10 nm or less exist is protruding, indicating that crystal grain growth is suppressed.
When added in excess of the upper limit of the components specified in each of the above, it is dispersed as a coarse second phase in the form of oxide, precipitate, crystallized product, etc., and when rolling to a plate thickness of 15 μm or less This is not preferable because it causes pinholes and plate breakage. Further, it is not preferable because the conductivity is remarkably lowered.
When the total amount of Cr, Zr and Ti is added below the lower limit of the components defined above, the heat resistance is lowered, which is not preferable.

The yield strength in the rolling vertical direction obtained with the rolled copper foil for the secondary battery current collector of the present invention is 600 MPa or more, more preferably 700 MPa or more, and further preferably 750 MPa or more. At the same time, the conductivity satisfies 60% IACS or higher. A more preferable range of the conductivity is 70% IACS or more, and a more preferable range is 75% IACS or more.
Moreover, the proof stress of the rolling vertical direction after the heat processing hold | maintaining at 350 degreeC for 1 hour which simulated the imidation heat processing of polyimide is 350 Mpa or more, More preferably, it is 400 Mpa or more, More preferably, it is 510 Mpa or more.

  The inevitable impurities referred to in the present specification are generally present in metal products and are inevitably mixed in the manufacturing process, and are originally unnecessary, but are trace amounts, It is an acceptable impurity because it does not affect the product characteristics.

[Process for controlling crystal orientation]
The manufacturing process for controlling to the crystal orientation in which effectiveness was found in embodiment of this invention is shown. Note that, as described above, the rolled copper foil for the secondary battery current collector of the present invention is a process shown here as long as the area ratio of the region in which the (111) crystal plane is oriented in the rolling vertical direction is satisfied. It is not limited to what was manufactured by.

As a manufacturing process of the rolled copper foil for controlling the crystal orientation, the first process step 1 to the tenth process step 10 are basic processes as shown in FIG. In addition, tempering and low-temperature annealing may be performed after the tenth process step 10 for the purpose of slightly improving elongation and adjusting characteristics.
However, in these steps, it is desirable to combine the preferable conditions in the present invention. In particular, it is important to select a combination of the conditions of Step 5 and Step 9.

-High temperature rolling 2 (step 5):
The high-temperature rolling 2 in step 5 is performed at a processing temperature of 400 ° C. or higher and lower than 600 ° C., more preferably 420 ° C. or higher and 580 ° C. or lower, more preferably 440 ° C. or higher and 560 ° C. or lower. More preferably, it is 50% or more, and further preferably 55% or more. The upper limit of the processing rate is 85% because of the suppression of edge cracks. The processing temperature was measured with a radiation thermometer before and after the pass. These conditions are performed in order to increase the region where the (111) crystal plane is oriented in TD.

Heat treatment (Step 9):
The heat treatment in Step 9 is performed at a temperature of 400 ° C. or higher and 500 ° C. or lower, more preferably 405 ° C. or higher and 495 ° C. or lower, more preferably 410 ° C. or higher and 490 ° C. or lower, for 0.5 hours to 3 hours, preferably from 0.8 hours. 2.7 hours, more preferably in the range of 1 hour to 2.3 hours.
At temperatures lower than this, precipitation of the main components Cr, Zr, and Ti becomes insufficient, and the electrical conductivity is lowered. At a temperature higher than this, the region in which the (111) crystal plane is oriented in TD decreases due to the randomization of the crystal orientation accompanying the coarsening of the recrystallized grains, and the proof stress decreases.

[Foil thickness]
In this embodiment, for the purpose of improving the energy density of the battery, a copper foil having a thickness of 15 μm or less is particularly targeted. However, the present invention can also be applied to a copper foil thicker than 15 μm. Specifically, the copper foil of the present invention can be applied to those having a thickness of about 5 μm to 25 μm.

  Hereinafter, the present invention will be described in more detail based on examples, but the present invention is not limited thereto.

[Method for producing rolled copper foil]
The Example of the manufacturing method of the rolled copper foil for secondary battery collectors which concerns on this embodiment is demonstrated with reference to FIG. The present invention is not limited to this.

  In Step 1, the raw material was melted in a vacuum melting furnace, and in Step 2, the melted raw material was cooled and cast at a cooling rate of 0.1 to 100 ° C./second to obtain an ingot. The ingot contained the alloy components shown in Table 2, and the remainder was formed of Cu and inevitable impurities.

In Step 3, a homogenization heat treatment was performed at 900 to 1030 ° C. for 5 minutes to 4 hours, and in Step 4, high-temperature rolling 1 was performed at a processing rate of 40 to 95% and a temperature of 600 to 1030 ° C. Next, high-temperature rolling 2 was performed in step 5 under the conditions shown in Table 1. The processing temperature of the material was measured with a radiation thermometer and a contact thermometer.
Next, water cooling was performed at Step 6, chamfering was performed to remove oxide scale at Step 7, and intermediate cold rolling with a processing rate of 90.0 to 99.9% was performed at Step 8 in order.
Next, the heat treatment of Step 9 was performed under the manufacturing conditions shown in Table 1.
Next, in step 10, final cold rolling with a processing rate of 66 to 95% was performed to prepare a test material having a thickness of 6 to 15 μm.

The compositions and properties of these inventive examples 101 to 111 and comparative examples 201 to 203, 301 to 306 are as shown in Table 2.
After each heat treatment and rolling, acid cleaning and surface polishing were performed according to the state of oxidation and roughness of the material surface, and correction with a tension leveler was performed according to the shape.

  The following evaluation was performed about this rolled copper foil.

[Area ratio of region in which (111) plane is oriented in the vertical direction of rolling: (TD (111))]
The area ratio of the region in which the (111) plane was oriented in the rolling direction was measured from the rolling surface by the above-described method by the EBSD method. In the case where the pattern was not clear because the work-affected layer on the rolled surface was thick, the measurement was performed after the electropolishing time was lengthened and the surface layer was melted around 1 μm thick.

[Rolling strength in the vertical direction: (YS)]
It was measured by a tensile test in the vertical direction of rolling according to JIS Z2241. The strain was calculated by measuring the distance between gauge points during a short-axis tensile test with a camera-type non-contact extensometer. And 0.2% yield strength was measured by the stress-strain curve. As the camera-type non-contact extensometer, DVE-201 (trade name) manufactured by Shimadzu Corporation was used. The elongation is measured by automatically tracking the mark mark from the CCD camera image. The test piece was formed in a strip shape having a width of 13 mm, and the test piece was collected in the direction of 90 ° with respect to the rolling direction.

[Conductivity: (EC)]
The measurement was performed at 20 ± 2 ° C. by the 4-terminal method.

[Area ratio of the region where the crystal plane is oriented within 15 degrees of deviation from the (111) plane in the rolling vertical direction after heating to 350 ° C .: (TD (111) after heating)]
After performing a heat treatment that is held at 350 ° C. for 1 hour in an Ar atmosphere, the area ratio of the region in which the crystal planes with a deviation from the (111) plane within 15 degrees in the rolling direction are oriented is determined by the EBSD method. It measured from the rolling surface by the method mentioned above. In the case where the pattern was not clear because the work-affected layer on the rolled surface was thick, the measurement was performed after the electropolishing time was lengthened and the surface layer was melted around 1 μm thick. In addition, after performing the heat processing hold | maintained at 350 degreeC for 1 hour, the area | region where the crystal plane orientation within 15 degrees of deviation | shift from a rolling direction (111) plane is maintained at 45% or less means that 350 degreeC Even if held at the following temperature for 1 hour, it can be considered that the orientation state of the crystal plane is the same.

[0.2% yield strength after heating to 350 ° C .: (YS after heating)]
After performing heat treatment held at 350 ° C. for 1 hour in an Ar atmosphere, it was measured by a tensile test in the rolling parallel direction according to JIS Z2241 in the same manner as before heating.
In order to set the boundary between elastic deformation and plastic deformation for the sake of convenience, the stress corresponding to the yield stress is taken as the proof stress, and the permanent strain at yield of steel is about 0.2% (0.002). The stress at which the permanent set is 0.2% is called 0.2% proof stress.
For Invention Example 104 and Comparative Example 204, not only 350 ° C. but also 0.2% proof stress after holding at 200 ° C. to 550 ° C. was measured in the same manner to collect softening curves. FIG. 5 shows the result.

  Table 2 shows the measurement results. Moreover, the measurement result of the relationship between stress and strain is shown in FIGS.

  As shown in Table 2, the scope of the present invention, that is, containing at least one of Cr, Zr and Ti in a total of 0.01 to 0.6 mass%, with the balance being composed of copper and inevitable impurities , A rolled copper foil made of a copper alloy formed by rolling, and satisfying that the area ratio of the region in which the crystal plane within 15 degrees of deviation from the (111) plane is oriented in the vertical direction of rolling is higher than 45% The yield strength “YS” in the vertical direction of rolling, the electrical conductivity “EC”, and the 0.2% yield strength “YS after heating” after heating to 350 ° C. were good. In terms of yield strength, “YS” was 600 MPa or higher, and “YS after heating” was 370 MPa or higher. Further, “EC” was 63% IACS or more, and a practically sufficient high conductivity was obtained.

  The crystal orientation distribution after heating at 350 ° C. is similar to that before heating, and the area ratio of the region where the crystal plane within 15 degrees from the (111) plane is oriented in the vertical direction of rolling is maintained at 45% or more. It was leaning. That is, it can be said that the copper foil of the present invention can maintain the crystal orientation state until heat treatment at 350 ° C. for about 1 hour, and can be said to be a heat-resistant copper foil.

  In addition, at least one of Cr, Zr, and Ti is contained in a total of 0.01 to 0.6 mass%, and at least one of Sn, Zn, Mn, Mg, and Ag is added in a total of 0.01 to 0.00 mass. It is a rolled copper foil containing 95 mass%, the balance being composed of copper and inevitable impurities, and made of a copper alloy formed by rolling, and the crystal plane whose deviation from the (111) plane is within 15 degrees is the rolling vertical direction When satisfying that the area ratio of the region oriented to higher than 45% is satisfied, the yield strength “YS” in the vertical direction of rolling, the electrical conductivity “EC”, the 0.2% yield strength after heating to 350 ° C. “YS after heating” Both were good. In terms of yield strength, “YS” was 670 MPa or more, “YS after heating” was 400 MPa or more, and both yield strength was high. Further, “EC” was 62% IACS or more, and a practically high conductivity was obtained.

  In particular, as shown in FIG. 6, “YS” was 770 MPa, and Example 104 of the present invention was able to obtain a large value. On the other hand, in Comparative Example 301, “YS” was 560 MPa as shown in FIG. Further, as shown in FIG. 5, Example 104 of the present invention showed good proof strength until after heating at 400 ° C. In Comparative Example 204 containing only the auxiliary additive element in the present invention, it was clearly softened at 350 ° C., and the strength as a current collector was insufficient.

  Therefore, since the rolled copper foil for a secondary battery current collector of the present invention can prevent the active material from being detached from the current collector, the charge / discharge cycle characteristics of the secondary battery can be improved. Therefore, it can provide as a rolled copper foil for secondary battery collectors suitable for a secondary battery.

Claims (5)

It is a rolled copper foil containing at least one of Cr, Zr and Ti in a total amount of 0.01 to 0.6 mass%, and the balance of copper and inevitable impurities,
A rolled copper foil for a secondary battery current collector in which the area ratio of a region in which a crystal plane whose deviation from the (111) plane is within 15 degrees is oriented in the vertical direction of rolling is higher than 45%. At least one of Cr, Zr and Ti is contained in a total of 0.01 to 0.6 mass%, and at least one of Sn, Zn, Mn, Mg and Ag is contained in a total of 0.01 to 0.95 mass%. Containing, the balance is a rolled copper foil made of copper and inevitable impurities,
A rolled copper foil for a secondary battery current collector in which the area ratio of a region in which a crystal plane whose deviation from the (111) plane is within 15 degrees is oriented in the vertical direction of rolling is higher than 45%.   The area ratio of the region in which the crystal plane whose deviation from the (111) plane is within 15 degrees after the heat treatment held at 350 ° C. for 1 hour is oriented in the vertical direction of rolling is higher than 45%. The rolled copper foil for secondary battery collectors of description. The ingot obtained by melting (step 1) and casting (step 2) the copper alloy having the alloy composition of the rolled copper foil for a secondary battery current collector according to claim 1 or 2 is 900 to 1030. Homogenized heat treatment (step 3) for 5 minutes to 4 hours at ℃, hot rolling 1 (step 4) and hot rolling 2 (step 5) at a processing rate of 40 to 95% at a temperature of 600 to 1030 ℃, cooling (step 6) Face milling (step 7), intermediate cold rolling (step 8) and heat treatment (step 9) with a processing rate of 90.0 to 99.9%, and final processing with a processing rate of 66 to 95% A method for producing a rolled copper foil for a secondary battery current collector, which is subjected to cold rolling (step 10),
The high temperature rolling 2 (step 5) is performed at a processing temperature of 400 ° C. to 600 ° C. and a processing rate of 50% to 70%, and the heat treatment (step 9) is 400 ° C. to 450 ° C. for 0.5 hours to 3 hours. Hold,
Alternatively, the high temperature rolling 2 (step 5) is performed at a processing temperature of 400 ° C. to 600 ° C. and a processing rate of 20% to 40%, and the heat treatment (step 9) is performed at 450 ° C. to 500 ° C. for 0.5 hours. The manufacturing method of the rolled copper foil for secondary battery electrical power collectors hold | maintained for 3 hours. The method for producing a rolled copper foil for a secondary battery current collector according to claim 4, wherein low-temperature annealing is performed after the final cold rolling (step 10).