Metal foil

Abstract

This metal foil is provided with: a core part which has a first surface and a second surface on the opposite side thereof and which is formed from a metal material; the present invention relates to a metal foil which comprises a core part and a cladding part which is positioned on at least one surface of the core part and which has zinc as a base material, and wherein, when X-ray diffraction measurement is performed on each of both surfaces of the metal foil, the intensity ratio of the peak intensity S (002) of a peak derived from the (002) plane of zinc to the peak intensity S (101) of a peak derived from the (101) plane of zinc on each of the surfaces is 1.01 or more.

Description

Technical Field

[0001] The present invention relates to a metal foil having a core portion formed of a metal material and a clad portion having zinc as a base material. Background Art

[0002] Conventionally, a metal foil containing zinc has been used for a negative electrode active material of a battery or the like. For example, the present applicant previously proposed a zinc foil and a negative electrode active material for a primary battery using the same, the zinc foil containing bismuth, the balance being composed of zinc and inevitable impurities, and the average size of the crystal grains of zinc being 0.2 μm or more and 8 μm or less (see Patent Document 1). This zinc foil has the following advantages: when this zinc foil is used as a negative electrode active material of a battery, the amount of gas generation during long-term storage of the battery can be suppressed as compared with the case of using a conventional rolled zinc foil.

[0003] In recent years, secondary batteries using zinc as a negative electrode active material, such as an air / zinc secondary battery and a manganese / zinc secondary battery, have attracted attention. These secondary batteries effectively utilize the economy and safety of zinc and are expected to be used as large-capacity next-generation storage batteries in mobile devices, unmanned aerial vehicles, or the like.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: US2022 / 0037654A1 Summary of the Invention

[0007] When a zinc foil is used as a negative electrode active material of a secondary battery, shape stability during long-term storage is required.

[0008] However, the inventors conducted research and as a result, determined that: conventional zinc foils sometimes warp or elongate during long-term storage, and there is room for improvement in shape stability.

[0009] An object of the present invention is to provide a technique that can eliminate the problems of the above-mentioned prior art.

[0010] The present inventors conducted intensive research and as a result, found that: the above problems can be solved by a metal foil in which a clad portion having zinc as a base material is combined with a core portion formed of a metal material and which has a specific crystal orientation of zinc on both surfaces.

[0011] Based on the above recognition, the present invention provides a metal foil having:

[0012] a core portion having a first surface and a second surface located on the opposite side thereof, and formed of a metal material; and

[0013] A cladding portion, which is located on at least one surface of the above-mentioned core portion and uses zinc as the base material,

[0014] Among them, when X-ray diffraction measurements are respectively performed on both sides of the above-mentioned metal foil, in any one side, the peak intensity S of the (002) plane derived from zinc (002) relative to the peak intensity S of the (101) plane derived from zinc (101) of the intensity ratio (hereinafter, also referred to as "S (002) / S (101) ".) is 1.01 or more. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 is a captured image of software used to calculate the grain size of zinc.

[0016] Figure 2 is a schematic diagram showing the area between electrodes used to calculate the circulation rate of the electrolyte.

[0017] Figure 3 is a schematic diagram explaining the size of the metal foil. (1) is a three-dimensional view of the metal foil, and (2) is a view obtained by observing the metal foil from the side.

[0018] Figure 4 is the X-ray diffraction measurement result of the metal foil of Examples 1 to 4.

[0019] Figure 5 is the X-ray diffraction measurement result of the metal foil of Comparative Examples 1 to 3. DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, preferred embodiments of the present invention will be described.

[0021] The metal foil of the present embodiment has a core portion and a cladding portion located on at least one surface of the core portion. In the present embodiment, the metal foil is obtained by electrogalvanizing. The core portion corresponds to the base material disposed as a cathode in the electrolytic plating using an electrolyte containing zinc ions, and the cladding portion corresponds to the electrolytic layer deposited on the base material with zinc as the base material. Hereinafter, the core portion and the cladding portion will be further described respectively.

[0022] In the present embodiment, the core portion has a first surface and a second surface located on the opposite side thereof. The first surface and the second surface are preferably parallel to each other. The core portion of the present embodiment is in the form of a foil like the metal foil. The foil has a thickness direction in a direction orthogonal to the first surface and the second surface. Thus, as the shape of the core portion of the present embodiment having the first surface and the second surface located on the opposite side thereof, a flat shape that is thinly extended can be cited. The shape of the core portion is sometimes referred to as film-like, sheet-like, or layer-like. The central position in the thickness direction in the metal foil of the present embodiment may be located in the core portion or may be located in the cladding portion.

[0023] The core portion is formed of a metal material. The metal material has a metal as its base material. From the viewpoints of the stability of the size and shape during long-term storage as a base material, ease of acquisition, etc., as the base metal constituting the core portion, copper, zinc, aluminum, etc. can be cited, and from the viewpoints of the ease of formation of the cladding portion, the adhesion to the cladding portion, and prevention of passivation, at least one selected from copper and zinc is particularly preferred. Accordingly, the core portion is particularly preferably at least one selected from copper foil and zinc foil.

[0024] The so-called having a metal as the base material means that the metal has a content rate of 80% by mass or more. The content of the metal in the core portion can be 90% by mass or more, can be 95% by mass or more, can be 99% by mass or more, or can be 99.5% by mass or more. Particularly, when the metal is at least one selected from copper and zinc, a content above the above lower limit is preferred. Therefore, when the base metal constituting the core portion is copper, the content of copper in the core portion can be 90% by mass or more, can be 95% by mass or more, can be 99% by mass or more, or can be 99.5% by mass or more. Further, when the base metal constituting the core portion is zinc, the content of zinc constituting the core portion can be 90% by mass or more, can be 95% by mass or more, can be 99% by mass or more, or can be 99.5% by mass or more.

[0025] Both surfaces of the metal foil of the present embodiment have a predetermined peak intensity ratio derived from zinc when subjected to X-ray diffraction measurement. That is, zinc exists on the surfaces of both surfaces of the metal foil. Therefore, when the core portion of the metal foil has a metal other than zinc as the base material, a cladding portion having zinc as the base material is formed on both surfaces of the core portion. On the other hand, when the core portion of the metal foil has zinc as the base material, since zinc exists on the surface of the core portion itself, when one surface of the surface of the core portion satisfies the above peak intensity ratio, for the surface of the core portion, a cladding portion can be formed only on one surface or can be formed on both surfaces.

[0026] In terms of reducing manufacturing costs in addition to shape stability after long-term storage, a metal foil with a copper foil core is also preferred. As the copper foil, either an electrolytic copper foil or a rolled copper foil can be used. When the core is a copper foil, a cladding portion with zinc as the base material is formed on both sides of the copper foil. In the cladding portions formed on both sides of the copper foil, the peak intensity S of the peak from the (002) plane of zinc (002) relative to the peak intensity S of the peak from the (101) plane of zinc (101) of the intensity ratio S (002) / S (101) is 1.01 or more for both. It should be noted that in this specification, the "electrode surface" of the electrolytic foil refers to the side surface that comes into contact with the cathode during the production of the electrolytic foil (such as an electrolytic copper foil). In addition, in this specification, the "deposited surface" of the electrolytic foil refers to the side surface on which the electrolytic metal (such as electrolytic copper) gradually deposits during the production of the electrolytic foil, that is, the side surface that does not come into contact with the cathode.

[0027] When the core is a copper foil, it is preferably composed of copper, additive elements, and inevitable impurities or composed of copper and inevitable impurities.

[0028] As the additive elements in the case where the core is a copper foil, at least one selected from the group consisting of tin, zinc, aluminum, iron, nickel, manganese, beryllium, tungsten, titanium, boron, cerium, lanthanum, praseodymium, and neodymium can be cited.

[0029] As the inevitable impurities in the case where the core is a copper foil, sulfur, phosphorus, and oxygen can be cited. The amount of each of the above inevitable impurities in the core is preferably 100 ppm or less, more preferably 10 ppm or less, on a mass basis. It should be noted that the content of each of the various additive elements listed above can also be an amount below the upper limit that is the same as the upper limit of the inevitable impurities. That is, for each of the metals selected from the group consisting of tin, zinc, aluminum, iron, nickel, manganese, beryllium, tungsten, titanium, boron, cerium, lanthanum, praseodymium, and neodymium, it can also be 100 ppm or less, or 10 ppm or less, respectively, on a mass basis in the core.

[0030] The amounts of the respective additive elements and inevitable impurities described in this specification can all be used independently. For example, for the amounts of each of the 14 elements from tin to neodymium, they can also be used alone or in any combination.

[0031] When the core is a zinc foil, it is preferred because of its particularly excellent suitability for secondary batteries. As the zinc foil, either an electrolytic zinc foil or a rolled zinc foil can be used. When the zinc foil is an electrolytic zinc foil, by forming a cladding portion on at least the electrode surface among the electrode surface and the deposited surface of the electrolytic zinc foil, it is possible to easily obtain S on either surface when performing X-ray diffraction measurement on both sides of the metal foil(002) / S (101) They are all metal foils with a value of 1.01 or more, so they are preferred.

[0032] In addition, when the core is a rolled zinc foil, forming cladding portions on both sides of the core can easily obtain S in either side when performing X-ray diffraction measurement on both sides of the metal foil. (002) / S (101) They are all metal foils with a value of 1.01 or more, so they are preferred.

[0033] When the core is a zinc foil, it is preferably composed of zinc, additive elements and inevitable impurities or composed of zinc and inevitable impurities.

[0034] As the additive elements in the case where the core is a zinc foil, at least one selected from the group consisting of bismuth, indium, magnesium, calcium, gallium, tin, barium, strontium, silver and manganese can be cited.

[0035] As the inevitable impurities in the case where the core is a zinc foil, iron, copper, lead, cadmium, nickel, chromium, sodium and potassium can be cited. In the case where the core is a zinc foil, the amount of the above-mentioned inevitable impurities is preferably 100 ppm or less, more preferably 10 ppm or less, respectively, in the core. It should be noted that the content of various additive elements listed above can also be an amount below the same upper limit as the preferred upper limit of these inevitable impurities. That is, for each of the above-mentioned metals selected from the group consisting of bismuth, indium, magnesium, calcium, gallium, tin, barium, strontium, silver and manganese, it can also be 100 ppm or less, and can also be 10 ppm or less, respectively, in the core on a mass basis.

[0036] The content ratios of copper, zinc, the above-mentioned additive elements and the inevitable impurities in the core are measured by sampling the core from the zinc foil and subjecting it to ICP emission spectrometry. After dissolving the sample in an acidic solution such as nitric acid or hydrochloric acid, the concentration of the metals other than zinc is measured by ICP emission spectrometry, the solution concentration of all metals is set to 1, and the content ratios of various metal elements are converted into mass. As a sampling method for the core, after confirming the position of the core through observation in a scanning electron microscope described later, in the case where the cladding portion is located on only one side of the core, it is only necessary to shave the core side surface with a milling cutter, a file, etc. and perform sampling. In addition, in the case where the cladding portion is located on both sides of the core, the cladding portion can be removed with a milling cutter, a file, etc. to obtain a sample formed by the core.

[0037] From the viewpoint of making the stability of the shape and dimensions excellent, the thickness Wr of the core part is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 15 μm or more. Further, from the aspect of flexibility, the thickness Wr of the core part is preferably 300 μm or less, more preferably 200 μm or less, and still more preferably 150 μm or less. From these aspects, as a range, the thickness Wr of the core part is preferably 5 μm or more and 300 μm or less, more preferably 10 μm or more and 200 μm or less, and still more preferably 15 μm or more and 150 μm or less.

[0038] In the case where the above core part is a copper foil, from the viewpoints of making the elongation property of the zinc foil excellent and improving the repeated flexibility, the average size of the copper grains in the core part is preferably 5 μm or more, more preferably 10 μm or more, and still more preferably 100 μm or less. Further, from the aspect of making the advantage of reducing the gas generation amount more remarkable, the average size of the zinc grains in the above cladding part is preferably 80 μm or less, more preferably 60 μm or less, and still more preferably 40 μm or less.

[0039] In the case where the above core part is a zinc foil, from the viewpoints of making the elongation property of the zinc foil excellent and improving the repeated flexibility, the average size of the zinc grains in the core part is preferably 24 μm or more, more preferably 35 μm or more, and still more preferably 100 μm or less. Further, from the aspect of making the advantage of reducing the gas generation amount more remarkable, the average size of the zinc grains in the above cladding part is preferably less than 100 μm, more preferably 50 μm or less, and still more preferably 10 μm or less.

[0040] It should be noted that the core part may contain bismuth or may not contain bismuth. The fact that the core part substantially does not contain bismuth preferably means that the bismuth content of the core part is 90 mass ppm or less.

[0041] The cladding part is located on at least one surface of the core part. The cladding part may be formed on only one of the two surfaces of the core part, or may be formed on both surfaces, but it is preferable that the cladding part is formed on both surfaces of the core part because of the excellent shape stability during long-term storage. In the present embodiment, the cladding part is a layer laminated with the core part. Further, in the present embodiment, the cladding part is formed in such a manner as to be in direct contact with the core part. On the surface of the core part where the cladding part is located, the cladding part may cover the entire surface of the core part or may cover a part thereof.

[0042] The cladding part uses zinc as a base material. The meaning of "using zinc as a base material" is the same as that of the core part. The content of zinc in the cladding part may be 90 mass% or more, may be 95 mass% or more, may be 99 mass% or more, or may be 99.5 mass% or more.

[0043] The cladding portion may or may not contain bismuth. For example, as the composition of the cladding portion, it may be composed of zinc, bismuth, additive elements other than bismuth, and inevitable impurities, or it may be composed of zinc, bismuth, and inevitable impurities, or it may be composed of additive elements other than zinc and bismuth, and inevitable impurities, or it may be composed of zinc and inevitable impurities. The cladding portion may or may not be an alloy.

[0044] When the cladding portion contains additive elements other than bismuth, it is advantageous to use a metal element having a hydrogen overvoltage (which may also be referred to as hydrogen overpotential) higher than that of zinc or a redox potential more noble than that of zinc. Examples of such metal elements include at least one selected from the group consisting of indium, magnesium, calcium, gallium, tin, barium, strontium, silver, and manganese. The amount of the above-mentioned additive elements in the cladding portion is preferably 10,000 ppm or less, more preferably 8,000 ppm or less, in terms of the total proportion of indium, magnesium, calcium, gallium, tin, barium, strontium, silver, and manganese based on mass. In addition, when containing additive elements selected from indium, magnesium, calcium, gallium, tin, barium, strontium, silver, and manganese, it is preferably 10 ppm or more in total based on mass.

[0045] Examples of the inevitable impurities in the cladding portion include iron, copper, aluminum, lead, cadmium, nickel, chromium, sodium, and potassium. The above-mentioned inevitable impurities in the cladding portion are preferably 100 ppm or less, more preferably 10 ppm or less, in terms of the total proportion of iron, copper, aluminum, lead, cadmium, nickel, chromium, sodium, and potassium based on mass. In addition, there are cases where magnesium and calcium are inevitable impurities. In this case, the total of iron, copper, aluminum, lead, cadmium, nickel, chromium, sodium, potassium, magnesium, and calcium is preferably 100 ppm or less, more preferably 10 ppm or less.

[0046] When the cladding portion contains bismuth, gas generation during battery storage can be effectively suppressed. When the cladding portion contains bismuth, regarding its content ratio, the content ratio of bismuth in the cladding portion is preferably 100 ppm or more, more preferably 300 ppm or more, and further preferably 400 ppm or more, based on mass. In addition, by having the content ratio of bismuth in the cladding portion be 10,000 ppm or less based on mass, it has the advantage of uniform dispersion within the cladding portion, so it is preferably 3,000 ppm or less, more preferably 1,200 ppm or less. On the other hand, from the viewpoint of further improving the shape stability of the metal foil of the present embodiment, the cladding portion preferably substantially does not contain bismuth. Substantially not containing bismuth preferably means that the content ratio of bismuth in the cladding portion is 90 ppm or less.

[0047] When the cladding portion contains bismuth, the amount of deformation over time tends to increase. However, in the present invention, even in such a case, the amount of deformation over time can be reduced. Therefore, it is preferable in terms of obtaining the effect of reducing the amount of gas due to the bismuth content and at the same time reducing the amount of deformation over time.

[0048] In addition, when the cladding portion does not contain bismuth, it is preferable in terms of being able to further reduce the amount of deformation over time.

[0049] The content ratios of zinc, each of the additive elements listed above, and each of the inevitable impurities listed above in the cladding portion are measured by sampling the cladding portion from a zinc foil and subjecting it to ICP emission spectrometry. The method of subjecting the sample to ICP emission spectrometry is the same as that for the core portion. As a sampling method for the cladding portion, after confirming the position of the cladding portion through observation with a scanning electron microscope described later, it is only necessary to shave off the surface of the zinc foil where the cladding portion is exposed with a milling cutter, file, etc. for sampling.

[0050] The average grain size of zinc in the above-mentioned cladding portion is preferably 2 μm or more. Since the zinc foil is maintained in a dense state, it is more preferably 20 μm or more, and further preferably 50 μm or less. In addition, from the aspect of making the advantage of reducing the gas generation amount more significant, the average grain size of zinc in the above-mentioned cladding portion is preferably less than 100 μm, more preferably 80 μm or less, and further preferably 50 μm or less. In order to produce grains of such a size in the cladding portion, it is suitable to manufacture the cladding portion by an electrolytic method.

[0051] When the cladding portion is formed on both sides of the core portion, it is only necessary to satisfy the above-mentioned average size in one cladding portion.

[0052] The average grain size of zinc is measured by the following method. For the measurement, a FE center gun type scanning electron microscope (SUPRA 55VP, manufactured by Carl Zeiss AG) equipped with an electron backscatter diffraction (hereinafter also referred to as "EBSD") evaluation device (OIM Data Collection Ver. 7.2.0, manufactured by TSL Solutions Co., Ltd.) and an attached EBSD analysis device are used. A sample with a cross-section cut out using an ultramicrotome is prepared, and for this sample, data on the grain size in a cross-sectional view capable of measuring the thickness of the entire sample is obtained according to the EBSD method. Specifically, for the grains in the core part, the grains are observed in a field of view of "core thickness × 200 μm in the direction perpendicular to the core thickness direction" in the cross-section of the entire zinc foil (cross-section along the thickness direction), and the average grain size of the grains is obtained. For the grains in the cladding part, the grains are observed in a field of view of "cladding thickness × 200 μm in the direction perpendicular to the cladding thickness direction" in the cross-section of the entire zinc foil, and the average grain size of the grains is obtained.

[0053] For the background processing of the EBSD measurement data, it is carried out under the condition that "Binning" is 4x4 (160x120) with the checkboxes of "Background Subtraction", "Normalize Intensity Histgram", and "Dynamic Background Subtraction" in the "ImageProccessing" of the above EBSD evaluation device cancelled. The "Gain" and "Exposure" can also be appropriately changed according to the image in the "Camera" so that Figure 1 the state where Kikuchi patterns cannot be observed in electron diffraction and the frame rate becomes 30 ± 1 fps. Under the condition that the value of "Ave" in the "ImageProccessing Function" is 10 under this condition, the background information is obtained by "Capture Bkd".

[0054] When measuring the grain size, the WD value is set to 15 ± 1 mm. With the options of "Background Subtraction", "Normalize Intensity Histgram", and "Dynamic Background Subtraction" selected in "Image Proccessing", select "Zn" for "Phase" in "Capture Pattern" of the above EBSD evaluation device at the observation site. Adjust the WD value under the conditions that the value of "Fit" in "Solutions" is within 1.5 and the value of "CI" is higher than 0.1.

[0055] The grain size is measured by "StartScan" on the photo of the sample cross-section taken from "Capture SEM" in "Scan".

[0056] For this measurement data, use "All data" in the "Grain Size Quick Chart" of the analysis menu of the EBSD analysis program (OIM Analysis Ver. 7.3.1, manufactured by TSL Solutions Co., Ltd.) to obtain the average grain size (Grain Size (Average)). Take this average grain size as the average size of the zinc grains in the present invention.

[0057] In this measurement, an orientation difference of 15° or more is regarded as a grain boundary. However, since the crystal structure of zinc is a hexagonal close-packed structure, considering twin grain boundaries, when the orientation difference at a certain grain boundary is represented by a rotation axis and a rotation angle, the cases where the rotation axis is represented by the following (1) and the rotation angles are 94.8 ± 1° and 57 ± 1°, and the cases where the rotation axis is represented by the following (2) and the rotation angles are 34.8 ± 1° and 64.3 ± 1° are not regarded as grain boundaries. The conditions of the scanning electron microscope during observation are set as follows: acceleration voltage: 20 kV, aperture: 60 μm, High Current mode, specimen angle: 70°. The observation magnification, measurement area, and step size can also be appropriately changed according to the size of the grains.

[0058] [Mathematical formula 1]

[0059]

[0060] It should be noted that the above is an explanation of the method for obtaining the average size of zinc grains. However, when measuring the average size of copper grains, in the above description of the measurement method, only need to select "Cu" instead of selecting "Zn" for "Phase" in "Capture Pattern" of the above EBSD evaluation device at the observation site.

[0061] From the viewpoint of shape stability during long-term storage, the thickness Wd of the cladding portion is preferably 5 μm or more, more preferably 20 μm or more, and still more preferably 40 μm or more. A thickness Wd of the cladding portion below 300 μm is preferred in terms of manufacturing a thin battery, more preferably 250 μm or less, and still more preferably 150 μm or less. From these aspects, the thickness Wd of the cladding portion is preferably 5 μm or more and less than 300 μm, more preferably 20 μm or more and 250 μm or less, and still more preferably 40 μm or more and 150 μm or less.

[0062] When the cladding portions are disposed on both sides of the core portion, the thickness of the cladding portion is set to the average value of the respective thicknesses on both sides.

[0063] When the cladding portion has two sides, it is preferred that the thickness of each cladding portion falls within the above range. It should be noted that when the cladding portion has two sides, the thicknesses of the respective cladding portions may be the same or different, but from the viewpoint of suppressing warping of the metal foil, the thicknesses of the cladding portions on both sides are preferably the same. The difference in thickness between the cladding portions on both sides is preferably 50 μm or less, more preferably 20 μm or less.

[0064] The thicknesses of the core portion and the cladding portion can be obtained by observing a cross section along the thickness direction of the metal foil with a scanning electron microscope (SEM), detecting the interface between the core portion and the cladding portion, and measuring the thicknesses of the core portion and the cladding portion, respectively.

[0065] However, during the manufacture of the metal foil, by using the thickness of the core portion as the raw material and subtracting this thickness from the value of the thickness of the manufactured metal foil, the thickness of the cladding portion can also be obtained.

[0066] When the thickness of the core portion is set to Wr and the thickness of the cladding portion is set to Wd, Wd / Wr is preferably 4 or less in terms of ease of manufacture. In particular, Wd / Wr is preferably 0.99 or less from the viewpoint of further excellent shape stability effect during long-term storage, more preferably 0.8 or less, and particularly preferably 0.7 or less. For Wd / Wr, Wd / Wr is preferably 0.1 or more, more preferably 0.2 or more, and particularly preferably 0.3 or more from the viewpoint of uniformly forming the cladding portion. From these aspects, Wd / Wr is preferably 0.1 or more and 4.0 or less, more preferably 0.1 or more and 0.99 or less, further preferably 0.2 or more and 0.8 or less, and particularly preferably 0.3 or more and 0.7 or less.

[0067] For the metal foil of the present invention, when X-ray diffraction measurements are respectively performed on both sides of the metal foil, a peak derived from the (002) plane of zinc is observed. More specifically, for the metal foil, when X-ray diffraction measurements are respectively performed on both sides of the metal foil, in any one side, S(002) / S (101) are all 1.01 or more. In this way, by having a core formed of a metal material and having the same zinc orientation on both sides thereof, the metal foil of the present invention becomes a metal foil having good shape stability after long-term storage. In addition, S in each of the two sides of the metal foil (002) / S (101) being 1.01 or more is also preferable from the aspect of preventing the generation of dendrites.

[0068] In addition, as a structure in which S (002) / S (101) is easily measurable, the metal foil preferably has the surface with zinc as the base material as the outermost layer on both sides thereof.

[0069] For the metal foil, when X-ray diffraction measurements are respectively performed on both sides of the metal foil, S (002) / S (101) is more preferably 1.01 or more, and even more preferably 1.10 or more. S in the metal foil (002) / S (101) value may become infinitely large (especially when the intensity of S (101) is small), so the upper limit is not limited. The peak intensity ratio described in this specification is the peak height ratio.

[0070] The (002) plane of zinc is derived from a hexagonal crystal. S in each of the two sides of the metal foil (002) / S (101) The metal foil with the above lower limit or more can be obtained by forming an electrolytic layer with zinc as the base material on a substrate formed of a metal material using the electrolytic zinc plating method, and at this time, an appropriate manufacturing method described later is adopted.

[0071] For the metal foil of the present invention, when X-ray diffraction measurements are respectively performed on both sides of the metal foil, a peak derived from the (101) plane of zinc may or may not be observed. The (101) plane of zinc is derived from a hexagonal crystal.

[0072] The peak of the (002) plane of zinc in each side of the metal foil is usually observed in the range of 2θ = 36.30 ± 0.3°. In addition, the peak of the (101) plane of zinc in each side of the metal foil is usually observed in the range of 2θ = 43.24 ± 0.3°. Here, as the X-ray source in the X-ray diffraction measurement, Cu-Kα rays are used.

[0073] In the X-ray diffraction measurement using Cu-Kα rays as the X-ray source, in the range of 2θ = 15 to 120°, in each side of the metal foil, the peak of the (002) plane of zinc is preferably the peak with the maximum intensity.

[0074] In an X-ray diffraction measurement using Cu-Kα rays as an X-ray source, in the range of 2θ = 15 to 120°, in each surface of the metal foil, peaks other than the peak from the (002) plane of zinc and the peak from the (101) plane of zinc (hereinafter, also referred to as "other peaks") can also be observed, but from the aspect of achieving a uniform crystal arrangement, it is preferably not observed. When other peaks are observed, the peak intensity ratio of these peaks to the peak intensity of the peak from the (002) plane of zinc is preferably 0.99 or less, more preferably 0.9 or less.

[0075] The metal foil of the present invention is a metal foil having excellent shape stability after long-term storage. Specifically, when the metal foil is cut into a length of 190 mm and a width of 90 mm and sealed together with argon in an airtight container and stored under the conditions of a temperature of 80 °C, a relative humidity of 50%, and 96 hours, the deformation amount obtained by subtracting the size before storage from the size after storage is preferably 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.1 mm or less in the longitudinal direction.

[0076] In addition, when the metal foil is stored under the above conditions, the deformation amount obtained by subtracting the size before storage from the size after storage is preferably 0.5 mm or less, more preferably 0.3 mm or less, and still more preferably 0.1 mm or less in the transverse direction. Further, the warpage, which is the deformation amount in the height direction of the metal foil, is preferably 5 mm or less, more preferably 4 mm or less, and still more preferably 3 mm or less.

[0077] It should be noted that the longitudinal direction and the transverse direction are, for example, as shown in (1) of Figure 3 directions parallel to the plane of the metal foil and orthogonal to each other. The size of the longitudinal direction after storage is Figure 3 the maximum length of the longitudinal W in the sample shown in (1) of

[0078] In addition, the warpage is, as shown in (2) of Figure 3 the deformation amount of the height H when placed on a flat surface. It should be noted that this deformation amount is the difference between the height of the point that becomes the highest relative to the flat surface and the height before storage.

[0079] As shown in the following embodiments, each parameter of the above-mentioned metal foil is obtained by forming both sides of the metal foil of the present invention using an electrolytic plating method with an electrolytic layer having zinc as the base material. At this time, it can be obtained by adopting the appropriate manufacturing method described later, particularly by adopting an appropriate thickness in the core part and the cladding part, adjusting the electrolytic concentration or current density, and the immersion time in the electrolytic solution in the appropriate manufacturing method.

[0080] The core part is preferably combined with the cladding part in a non-separable manner. The core part and the cladding part being combined in a non-separable manner means that when observing the cross-section along the thickness direction of the metal foil with a scanning electron microscope, one or more grains having a shape spanning the interface between the core part and the cladding part are observed. Such a shape is caused by the grain growth of the grains in the cladding part in such a way that the orientation planes of the grains in the core part are made consistent. More specifically, in the cross-section along the thickness direction of the metal foil of the present embodiment, at the interface between the core part and the cladding part, a row of pore parts formed by a plurality of small pore parts is observed, and the position of the interface can be determined through this row of pore parts. When the scanning electron microscope image is a backscattered electron image, in this microscope image, due to the difference in the orientation planes of the grains, the shades of the colors of the individual zinc grains are different. Based on this difference in shade, the shape of the zinc grains can be determined. When one or more grains having a continuous shape spanning the interface between the core part and the cladding part are observed, it can be judged that the core part and the cladding part are combined in a non-separable manner, and preferably two or more are observed. It should be noted that the interface between the core part and the cladding part can also be confirmed by using EDS analysis (energy dispersive spectrometry) to confirm the existence positions of the metal elements or additive elements that are the base materials.

[0081] In order to combine the core part and the cladding part in a non-separable manner, it is sufficient to manufacture the metal foil by the appropriate manufacturing method described later.

[0082] From the viewpoint of reducing passivation, etc. in batteries such as secondary batteries, the metal foil may not contain aluminum. For example, in the metal foil, the content ratio of aluminum may be 1% or less, may be 0.1% or less, or may be 0.05% or less based on the mass of the metal foil.

[0083] From the viewpoint of reducing the environmental load, the metal foil preferably does not contain lead. For lead, the content ratio is preferably 200 ppm or less, more preferably 100 ppm or less, and still more preferably 50 ppm or less based on the mass of the metal foil. In addition, the metal foil may not contain cadmium or may contain it as an unavoidable impurity. The ratio of cadmium in the metal foil is preferably as low as possible. In particular, the content ratio of cadmium is preferably 10 ppm or less based on the mass.

[0084] The content ratios of aluminum, lead, and cadmium contained in the metal foil are measured by ICP emission spectrometry. For the measurement using ICP emission spectrometry, the same method as described above can be adopted.

[0085] The metal foil of the present invention is a thin metal foil preferably having a thickness of 15 μm or more and 900 μm or less, more preferably 25 μm or more and 500 μm or less, and still more preferably 30 μm or more and 300 μm or less. The thickness of the metal foil is measured by the method described above. Such a thin metal foil is suitable as a negative electrode material for secondary batteries, particularly for laminated secondary batteries such as bipolar batteries. In particular, the metal foil of the present invention has excellent shape stability during long-term storage, and thus is suitable as a metal foil for secondary batteries, particularly laminated secondary batteries.

[0086] Next, a preferred manufacturing method of the zinc foil of the present invention will be described.

[0087] This manufacturing method includes the following steps: using a substrate having a first surface and a second surface opposite thereto formed of a metal material as a cathode, and immersing the substrate in an electrolytic solution containing zinc ions at 10 to 90 °C for 1 to 10 minutes; and after this immersion step, electroplating at least one surface of the substrate using an electrolytic solution containing zinc ions to form an electroplated layer having zinc as a base material.

[0088] However, when X-ray diffraction measurement is performed on at least one surface of the above substrate, when S (002) / S (101) is less than 1.01, an electroplated layer having zinc as a base material is formed on at least this surface by electroplating.

[0089] As the description of the substrate, the description of the above core can be used.

[0090] Examples of the electrolytic solution containing zinc ions include aqueous zinc sulfate solution, aqueous zinc nitrate solution, aqueous zinc chloride solution, etc. The concentration of zinc contained in the electrolytic solution is preferably 30 g / L or more and 100 g / L or less, and more preferably 35 g / L or more and 90 g / L or less.

[0091] In addition, when the cladding portion contains bismuth, the electrolytic solution may contain bismuth ions in addition to zinc ions. Examples of the bismuth ion source include bismuth nitrate. When using the bismuth ions contained in the electrolytic solution, the ratio of the mass of bismuth to the total mass of zinc and bismuth in the electrolytic solution is preferably 10 ppm or more and 10,000 ppm or less, more preferably 15 ppm or more and 8,000 ppm or less, further preferably 20 ppm or more and 7,000 ppm or less, and still more preferably 30 ppm or more and 6,500 ppm or less, from the aspect of suppressing gas generation. When the electrolytic solution does not contain bismuth, the ratio of the mass of bismuth to the mass of zinc in the electrolytic solution is preferably less than 10 ppm, preferably 6 ppm or less, and further preferably 3 ppm or less.

[0092] The electrolytic solution may further contain other compounds. As the other compounds, for example, sulfuric acid may be added for the purpose of adjusting the pH of the electrolytic solution. As the pH of the electrolytic solution, at the time of electrolysis, 2 or less can be cited.

[0093] In this manufacturing method, before electrolytic plating using the electrolytic solution, the above-mentioned base material as the cathode is immersed in the above-mentioned electrolytic solution at 10 to 90 °C for 1 to 10 minutes. It becomes easy to obtain the S of the deposition surface deposited by the subsequent electrolytic plating (002) / S (101) to be a metal foil of 1.01 or more. From this viewpoint, the temperature of the electrolytic solution is more preferably 10 to 80 °C, and further preferably 15 to 35 °C. The immersion time before electrolytic plating is more preferably 3 to 8 minutes. The inventors believe that this pre-immersion has the effect of flattening the surface of the electrode (core part), and thus, it is easy to obtain the above-mentioned S of the deposition surface (002) / S (101) to be a metal foil of 1.01 or more.

[0094] In the electrolysis method, the anode and the cathode are immersed in an electrolytic solution containing a zinc source, and the cathode is used as the above-mentioned base material, and an electrolytic layer having zinc as the base material is deposited on its surface. It is preferable from the aspect of being able to easily obtain a cladding portion having a small average grain size. As the anode used in the electrolysis, it is preferable to use a known dimensionally stable electrode (DSE). As the DSE, for example, a titanium electrode coated with iridium oxide, a titanium electrode coated with ruthenium oxide, etc. are suitably used.

[0095] From the viewpoint of smoothly obtaining a metal foil with good shape stability, it is advantageous to circulate the electrolytic solution during electrolysis. To circulate the electrolytic solution, for example, as an electrolysis device, a device having a closed flow path, an electrolytic cell disposed in the flow path, and a pump disposed in the flow path is used, and the pump is driven to cause the electrolytic solution to flow through the electrolytic cell in one direction. The anode and cathode used in electrolysis may be immersed in the electrolytic cell in a state where the two face each other. The anode and cathode are preferably arranged in the electrolytic cell such that their opposing faces (the electrodeposition face in the case of the cathode) are parallel to the flow direction of the electrolytic solution.

[0096] When electrolysis is performed while circulating the electrolytic solution, it is advantageous to adjust the flow rate of the electrolytic solution, that is, the circulation rate, from the viewpoint of smoothly obtaining a zinc foil that exhibits the desired effects. Specifically, it is preferable to set the circulation rate of the electrolytic solution to 0.001 L / (min·mm 2 ) or more and 1 L / (min·mm 2 ) or less, more preferably set to 0.002 L / (min·mm 2 ) or more and 0.6 L / (min·mm 2 ) or less, further preferably set to 0.003 L / (min·mm 2 ) or more and 0.4 L / (min·mm 2 ) or less, and even more preferably set to 0.005 L / (min·mm 2 ) or more and 0.04 L / (min·mm 2 ) or less. The circulation rate is calculated by dividing the flow rate of the electrolytic solution (L / min) by the area between the electrodes (mm 2 ). The area between the electrodes is expressed as the product of the distance between the electrodes (mm) and the width of the electrodeposition electrode (mm) as shown in Figure 2 . In Figure 2 , it is preferable to cause the electrolytic solution to flow in a direction orthogonal to the plane of the paper. Further, in Figure 2 , the plate-shaped electrodes extend in a direction orthogonal to the plane of the paper.

[0097] The current density during electrolysis is one of the factors that affect the size of the zinc crystals in the obtained zinc foil. Specifically, by making the current density greater than the conditions for normal zinc electrolysis, many fine crystals can be generated, and thus it is possible to easily obtain a zinc foil with a small average grain size. From this viewpoint, it is preferable to set the current density to 1000 A / m 2 or more and 10000 A / m 2 or less, more preferably set to 1000 A / m 2 or more and 6000 A / m 2 or less, and further preferably set to 1000 A / m2 4000 A / m or more 2 and below.

[0098] The electrolytic solution can be supplied for electrolysis in a non-heated state or a heated state. When electrolysis is performed in a state where the electrolytic solution is heated, the temperature of the electrolytic solution is preferably set to 10°C or more and 90°C or less. More preferably, the temperature of the electrolytic solution is 20°C or more and 90°C or less, further preferably 30°C or more and 80°C or less, and even more preferably 30°C or more and 70°C or less. It is carried out until the thickness of the zinc foil becomes the target value.

[0099] The above electrolytic plating is preferably a single process. For example, when an electrolytic layer having zinc as a base material is formed on both sides of a substrate as a cladding portion by electrolytic plating, it is preferable to perform electrolytic plating in a state where both sides of the substrate are in contact with the electrolytic solution, so as to form an electrolytic layer having zinc as a base material on both sides at once.

[0100] The metal foil of the present invention obtained as described above is suitably used as a negative electrode active material for a secondary battery. Examples of the secondary battery include nickel / zinc batteries, air / zinc batteries, and manganese / zinc batteries. Furthermore, since the metal foil itself has conductivity, the metal foil also functions as a current collector. Thus, the metal foil itself can be used as a negative electrode without using a current collector. It should be noted that it can also be used as a negative electrode active material for a primary battery.

[0101] As shown in the evaluation results of the following examples, the battery having the metal foil of the present invention can be used as an electrode material with good shape stability even when stored at a high temperature for a long time. Thus, it can be suitably used for secondary batteries.

[0102] Based on the above understanding, the present invention provides the following [1] to [8].

[0103] [1] A metal foil, comprising:

[0104] a core portion having a first surface and a second surface located on the opposite side thereof, and formed of a metal material; and

[0105] a cladding portion located on at least one surface of the core portion and having zinc as a base material,

[0106] When X-ray diffraction measurement is performed on both surfaces of the metal foil, in any surface, the peak intensity S of the (002) plane derived from zinc (002) relative to the peak intensity S of the (101) plane derived from zinc (101) has an intensity ratio of 1.01 or more.

[0107] 〔2〕The metal foil according to 〔1〕, wherein the metal foil is cut into a length of 190 mm and a width of 90 mm, sealed together with argon in a hermetically sealable container, and when stored under the conditions of a temperature of 80 °C, a relative humidity of 50%, and 96 hours, the change in size after storage is 0.5 mm or less in the longitudinal direction and 0.5 mm or less in the transverse direction, and the warpage is 5 mm or less.

[0108] 〔3〕The metal foil according to 〔1〕 or 〔2〕, wherein the cladding portions are formed on both surfaces of the core portion.

[0109] 〔4〕The metal foil according to any one of 〔1〕 to 〔3〕, wherein the core portion and the cladding portions are integrally joined inseparably.

[0110] 〔5〕The metal foil according to any one of 〔1〕 to 〔4〕, wherein the core portion is a copper foil or a zinc foil.

[0111] 〔6〕The metal foil according to any one of 〔1〕 to 〔5〕, wherein the core portion is an electrolytic copper foil, a rolled zinc foil, an electrolytic zinc foil, or a rolled zinc foil.

[0112] 〔7〕The metal foil according to any one of 〔1〕 to 〔5〕, wherein the thickness of the core portion is 5 μm or more and 300 μm or less.

[0113] 〔8〕The metal foil according to any one of 〔1〕 to 〔6〕, wherein the thickness of the cladding portions is 5 μm or more and 300 μm or less.

[0114] 〔9〕The metal foil according to any one of 〔1〕 to 〔8〕, wherein in the core portion, the base metal is copper, or the core portion is a rolled zinc foil and the cladding portions are formed on both surfaces of the core portion, or

[0115] the core portion is an electrolytic zinc foil and the cladding portions are formed on at least the electrode surfaces thereof.

[0116] 〔10〕The metal foil according to any one of 〔1〕 to 〔9〕, wherein the cladding portions substantially do not contain bismuth.

[0117] 〔11〕An electrode material for a secondary battery, which comprises the metal foil according to 〔1〕 or 〔2〕.

[0118] Examples

[0119] Hereinafter, the present invention will be described in more detail by way of examples. However, the scope of the present invention is not limited to the described examples. Unless otherwise specified, "%" means "% by mass".

[0120] 〔Example 1〕

[0121] (1) Preparation of Substrate

[0122] As the substrate, an electrolytic copper foil (purity 99.9%, manufactured by Mitsui Mining & Smelting Co., Ltd.) having the thickness shown in Table 1 was prepared.

[0123] (2) Preparation of Electrolyte

[0124] As the zinc compound, zinc oxide was used. It was dissolved in water together with sulfuric acid to prepare the electrolyte. The concentration of zinc in the electrolyte was set to 50 g / L. The concentration of sulfuric acid was set to 200 g / L in terms of the value obtained by converting the total amount of sulfate ions into H2SO4. Bismuth nitrate was added to the electrolyte. The concentration of bismuth nitrate was adjusted so that the ratio of bismuth to the total mass of zinc and bismuth became 700 mass ppm. As the cathode, the above-mentioned electrolytic copper foil was used. The cathode was immersed in the electrolyte at 20°C for 5 minutes.

[0125] (3) Electrochemical Deposition of Zinc

[0126] As the anode, a DSE formed of a titanium electrode coated with iridium oxide was used.

[0127] An electric current was passed between the anode and the cathode while heating the electrolyte to 30°C. The current density was set to 2000 A / m 2 . The electrolyte was circulated at a circulation rate of 0.021 L / (min · mm 2 ). Electrolysis was carried out with both sides of the electrolytic copper foil immersed in the electrolyte, and an electrolytic zinc layer having an electrolytic thickness of the value described in Table 1 was formed on both sides of the electrolytic copper foil, obtaining a copper-zinc composite foil in which the electrolytic zinc layer and the electrolytic copper foil were integrated. In this composite foil, the electrolytic copper foil corresponds to the core part, and the electrolytic zinc layer corresponds to the cladding part. The obtained composite foil was washed with ion-exchanged water and dried by hot air.

[0128] 〔Example 2〕

[0129] In the processes of (2) and (3) of Example 1, bismuth nitrate was not used. Except for these points, a copper-zinc composite foil was obtained in the same manner as in Example 1.

[0130] 〔Example 3〕

[0131] In the process of (1) of Example 1, the substrate was changed from an electrolytic copper foil to a rolled zinc foil (purity 99.99%, manufactured by Sumitomo Metal Mining Co., Ltd.) having the thickness shown in Table 1. Except for this point, a composite foil in which the rolled zinc foil and the electrolytic zinc layer were integrated, i.e., a zinc foil, was obtained in the same manner as in Example 1.

[0132] 〔Example 4〕

[0133] (1) Manufacture of Electrolytic Zinc Foil as Substrate

[0134] As the zinc compound, zinc oxide is used. It is dissolved in water together with sulfuric acid to prepare an electrolytic solution. The concentration of zinc in the electrolytic solution is set to 50 g / L. The concentration of sulfuric acid is set to 200 g / L in terms of the value obtained by converting the total amount of sulfate ions into H2SO4. As the cathode, an aluminum plate is used. The cathode is immersed in the electrolytic solution at 30°C for 5 minutes.

[0135] As the anode, a DSE composed of a titanium electrode coated with iridium oxide is used.

[0136] A current is passed between the anode and the cathode while heating the electrolytic solution to 30°C. The current density is set to 2000 A / m 2 . The electrolytic solution has a circulation rate set to 0.021 L / (min · mm 2 ) and is circulated.

[0137] Electrolysis is carried out in this state, and an electrolytic zinc layer is formed on one side of the aluminum plate. After electrolysis, the electrolytic zinc layer is peeled off from the aluminum plate of the cathode to obtain zinc foil. The obtained zinc foil is washed with ion-exchanged water and dried by hot air.

[0138] (2) Manufacture of the cladding part

[0139] (2-1) As the zinc compound, zinc oxide is used. It is dissolved in water together with sulfuric acid to prepare an electrolytic solution. The concentration of zinc in the electrolytic solution is set to 50 g / L. The concentration of sulfuric acid is set to 200 g / L in terms of the value obtained by converting the total amount of sulfate ions into H2SO4.

[0140] (2-2) In Example 2, as the cathode, the deposition surface of the electrolytic zinc foil obtained in (1) is masked and then used. In addition, as the electrolytic solution, the electrolytic solution obtained in (2-1) is used. The unmasked electrode surface of the electrolytic zinc foil (the surface on the aluminum plate side in the process of (1)) is immersed in the electrolytic solution to carry out the immersion process and electroplating. Except for these points, the operation is the same as in Example 2, and an electrolytic zinc layer with an electrolytic thickness of the value recorded in Table 1 is formed on the electrode surface of the electrolytic zinc foil. Thus, a composite foil in which the electrolytic zinc layer and the electrolytic zinc foil are integrated, that is, zinc foil, is obtained.

[0141] 〔Comparative Example 1〕

[0142] This example is an example of manufacturing the same electrolytic zinc foil as in the example of Patent Document 1.

[0143] As the zinc compound, zinc oxide is used. It is dissolved in water together with sulfuric acid to prepare an electrolytic solution. The concentration of zinc in the electrolytic solution is set to 50 g / L. The concentration of sulfuric acid is set to 200 g / L in terms of the value obtained by converting the total amount of sulfate ions into H2SO4. Bismuth nitrate is added to the electrolytic solution. The concentration of bismuth nitrate is adjusted such that the ratio of bismuth to the total mass of zinc and bismuth becomes 700 mass ppm. As the cathode, an aluminum plate is used. The cathode is immersed in the electrolytic solution at 30 °C for 5 minutes.

[0144] As the anode, a DSE composed of a titanium electrode coated with iridium oxide is used.

[0145] With the electrolytic solution heated to 30 °C, an electric current is passed between the anode and the cathode. The current density is set to 2000 A / m 2 . The electrolytic solution has a circulation rate set to 0.021 L / (min · mm 2 ) and is circulated.

[0146] Electrolysis is carried out in this state, and an electrolytic zinc layer is formed on one side of the aluminum plate. After electrolysis, the electrolytic zinc layer is peeled off from the aluminum plate of the cathode to obtain zinc foil. The obtained zinc foil is washed with ion-exchanged water and dried by hot air.

[0147] [Comparative Example 2]

[0148] In the processes of (2) and (3) of Example 1, one side of the electrolytic copper foil used as the cathode is masked, and the electrolytic zinc layer is deposited only on one side. Except for this point, the operation is the same as in Example 1, and a copper-zinc composite foil in which the electrolytic zinc layer is formed on one side of the electrolytic copper foil and the electrolytic zinc layer and the electrolytic copper foil are integrated is obtained.

[0149] [Comparative Example 3]

[0150] In the processes of (2) and (3) of Example 3, one side of the rolled zinc foil used as the cathode is masked, and the electrolytic zinc layer is deposited only on one side. Except for this point, the operation is the same as in Example 3, and a composite foil in which the electrolytic zinc layer is formed on one side of the rolled zinc foil and the electrolytic zinc layer and the rolled zinc layer are integrated, that is, zinc foil, is obtained.

[0151] For the metal foils obtained in each of the examples and comparative examples, the following measurements / evaluations are carried out. The results are shown in Table 1.

[0152] The amount of bismuth in the cladding part of these metal foils is also shown in Table 1. The bismuth content in the cladding part is a value obtained by measuring the metal foils obtained in each of the examples / comparative examples by ICP emission spectrometry. Specifically, it is obtained by operating as follows.

[0153] In Example 1 and Comparative Example 2, the metal foil was dissolved in an aqueous nitric acid solution, the mass of Bi and the mass of Zn in the solution were determined, and "mass of Bi / (mass of Zn + mass of Bi)" was calculated.

[0154] In Example 3 and Comparative Example 3, the metal foil was dissolved in an aqueous nitric acid solution, and the Bi content in the solution was measured. In addition, the mass of zinc in the electrolytic plating solution after the formation of the cladding portion was measured by ICP emission spectrometry. The value obtained by subtracting this mass from the mass of zinc in the electrolytic plating solution before electrolytic plating was used as the mass of zinc in the cladding portion. From these, "mass of Bi / (mass of Zn in the cladding portion + mass of Bi)" was calculated.

[0155] Regarding the metal foil of Comparative Example 1, the metal foil was dissolved in an aqueous nitric acid solution, the mass of Bi and the mass of Zn in the solution were determined, and "mass of Bi / (mass of Zn + mass of Bi)" was calculated. However, since the metal foil of Comparative Example 1 only contains a core portion without a cladding portion, the amount of bismuth in the core portion is described in Table 1.

[0156] 〔XRD measurement conditions〕

[0157] An X-ray diffractometer (manufactured by Bruker Corporation, D8 ADVANCE) was used. The measurement conditions are as follows. The XRD measurement results of both sides of the metal foils obtained in Examples 1 to 4 are shown in Table 1 and Figure 4 In, the XRD measurement results of both sides of the metal foils obtained in Comparative Examples 1 to 3 are shown in Table 1 and Figure 5 In. The object surface for XRD measurement of the metal foil is as described in Table 1 (for the core portion, in the case of an electrolytic foil, the electrolytic surface or the deposited surface is described, and in the case of a rolled foil, the rolled surface is described. In addition, the presence or absence of a cladding portion is described).

[0158] · X-ray source: Cu-Kα ray

[0159] · Tube voltage: 40 kV

[0160] · Tube current: 40 mA

[0161] · Scanning speed: 10.5 deg / min

[0162] · Step size: 0.015 deg

[0163] · Scanning range: 2θ = 15 degrees to 120 degrees

[0164] 〔Evaluation (deformation amount over time)〕

[0165] The metal foils obtained in the examples and comparative examples were cut into pieces with a length of 190 mm and a width of 90 mm, placed on a flat surface, and the dimensions in the longitudinal, transverse, and height directions were measured. Then, the metal foils were put into a sealed container with the internal gas replaced by argon and sealed in an airtight state, and stored under the conditions of a temperature of 80 °C, a relative humidity of 50%, and 96 hours, and the dimensions were measured again. The dimensions were measured using a metal ruler. The deformation amount (mm) was obtained by subtracting the dimension after aging from the dimension before aging. The results are shown in Table 1.

[0166]

[0167] As shown in Table 1, in each of the examples, the deformation amount after aging was suppressed. In contrast, for Comparative Example 1 in which the S (002) / S (101) of the electrode surface of the electrolytic zinc foil was less than 1.01, the dimensional elongation over time was large. In addition, for the metal foils of Comparative Examples 2 and 3 in which the S (002) / S (101) of the surface without the electrolytic layer was less than 1.01, the warpage was large after long-term storage.

[0168] Industrial availability

[0169] According to the present invention, a zinc-containing metal foil excellent in shape stability during long-term storage can be provided.

Claims

1. A metal foil having: a core portion having a first surface and a second surface on the opposite side thereof, and formed of a metallic material; and a cladding portion located on at least one surface of the core portion and having zinc as a base material, Among them, When X-ray diffraction measurements are performed on both sides of the metal foil, in any one side, the peak intensity S of the (002) plane derived from zinc (002) relative to the peak intensity S of the (101) plane derived from zinc (101) is 1.01 or more for both intensity ratios.

2. The metal foil according to claim 1, wherein, When the metal foil is cut into a length of 190 mm and a width of 90 mm and stored under the conditions of a temperature of 80 °C, a relative humidity of 50%, and 96 hours, the change in size after storage is 0.5 mm or less in the longitudinal direction and 0.5 mm or less in the transverse direction, and the warpage is 5 mm or less.

3. The metal foil according to claim 1 or 2, wherein The cladding portion is formed on both surfaces of the core portion.

4. The metal foil according to claim 1 or 2, wherein The core portion and the cladding portion are joined in a non-separable manner.

5. The metal foil according to claim 1 or 2, wherein The core portion is a copper foil or a zinc foil.

6. The metal foil according to claim 1 or 2, wherein, The thickness of the core portion is 5 μm or more and 300 μm or less.

7. The metal foil according to claim 1 or 2, wherein The thickness of the cladding portion is 5 μm or more and 300 μm or less.

8. An electrode material for a secondary battery, comprising the metal foil according to claim 1 or 2.

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