Aluminum perforated foil and method for manufacturing same

Abstract

The present invention relates to an aluminum perforated foil suitable for a current collector for an electricity storage device and a method for manufacturing the same. The invention provides a method for manufacturing an aluminum perforated foil and an aluminum perforated foil. The present invention relates to a method for producing an aluminum perforated foil having a plurality of through-holes penetrating in the thickness direction, the method comprising: an alkali cleaning step for bringing a first aqueous composition containing 1-10 mass% of an alkali into contact with the surface of an aluminum foil; and a through-hole formation step for forming the through-hole in the thickness direction of the aluminum foil by bringing a second aqueous composition containing 1-30 mass% halide ions into contact with the surface of the aluminum foil within 20 minutes after the alkali cleaning step. The aluminum perforated foil has a prescribed breaking strength, average pore diameter, and maximum / average pore diameter.

Description

Technical Field

[0001] This invention relates to aluminum perforated foil and its manufacturing method. Background Technology

[0002] In recent years, the demand for energy storage devices, particularly lithium-ion capacitors (LIC), lithium-ion secondary batteries (LIB), and electric double-layer capacitors (EDLC), has increased in portable information terminals, portable electronic instruments, electric vehicles, hybrid electric vehicles, and stationary energy storage systems. As current collectors for the positive or negative electrodes of these energy storage devices, aluminum perforated foils with through-holes for pre-doping lithium ions are known.

[0003] For example, lithium-ion capacitors use the same activated carbon as double-layer capacitors as positive electrodes and the same carbon materials as lithium-ion secondary batteries as negative electrodes, which can achieve both high output density and high energy density. However, in order to achieve high capacity, it is necessary to efficiently pre-dope lithium ions and seek to form multiple micro-pores to make the air permeability of the aluminum open-cell foil low.

[0004] On the other hand, the tensile strength of aluminum perforated foil inevitably decreases when multiple through holes are formed. If the tensile strength of the aluminum perforated foil is too low, continuous processes such as roll-to-roll processes, which continuously process rolled strip current collectors through a conveyor line, cannot be used, resulting in poor production efficiency. Therefore, it is desirable to develop a technology that can suppress the decrease in tensile strength while maintaining a low air permeability value for the aluminum perforated foil.

[0005] Etching techniques are known as a method for forming micro-through holes.

[0006] For example, Patent Document 1 describes a method for forming through-holes on aluminum foil by electrolytic etching using an aqueous solution containing hydrochloric acid as the electrolyte. However, this method presents safety concerns due to the relatively high processing temperature. Furthermore, the high temperature and the cost associated with forming through-holes through electrolytic etching also contribute to the overall cost.

[0007] Furthermore, Patent Document 2 describes a method in which an aluminum oxide or aluminum hydroxide film is formed on the surface of an aluminum foil, the portion of the film to be formed into a through hole is removed by laser processing, and an aqueous solution containing sulfuric acid and nitric acid is used as an electrolyte to form a through hole on the aluminum foil by electrolytic etching. However, this method involves many steps and incurs costs due to the use of a laser.

[0008] Existing technical documents

[0009] Patent documents

[0010] Patent Document 1: Japanese Patent Application Publication No. 2011-208254

[0011] Patent Document 2: International Publication No. 2017 / 163913 Summary of the Invention

[0012] The problem the invention aims to solve

[0013] The requirement is to develop aluminum perforated foil suitable for use as a current collector in energy storage devices and its manufacturing technology.

[0014] Solution for solving the problem

[0015] This invention relates to the aluminum perforated foil shown below and its manufacturing method.

[0016] [1] A method for manufacturing an aluminum perforated foil, wherein the aluminum perforated foil has a plurality of through holes extending in the thickness direction, the manufacturing method comprising:

[0017] The alkaline cleaning process involves contacting a first aqueous composition containing 1% by mass and less than 10% by mass of an alkali with the surface of the aluminum foil; and

[0018] In the through-hole forming process, within 20 minutes after the alkaline cleaning process, a second aqueous composition containing more than 1% and less than 30% by mass of halide ions is brought into contact with the surface of the aluminum foil, thereby forming the through-hole in the thickness direction of the aluminum foil.

[0019] [2] According to the manufacturing method of aluminum perforated foil described in [1] above, wherein the alkali is an alkali metal or alkaline earth metal hydroxide.

[0020] [3] The method for manufacturing aluminum perforated foil according to the above [1] or [2], wherein the halide ion is a chloride ion.

[0021] [4] The method for manufacturing aluminum perforated foil according to any one of [1] to [3] above, wherein the thickness of the aluminum foil is 1 μm or more and 50 μm or less.

[0022] [5] The method for manufacturing aluminum perforated foil according to any one of [1] to [4] above, wherein the aluminum purity of the aluminum foil is 98% by mass or more and less than 99.9% by mass.

[0023] [6] The method for manufacturing aluminum perforated foil according to any one of [1] to [5] above, wherein the processing temperature in the alkaline cleaning process is above 10°C and below 50°C, and the processing time is above 5 seconds and below 120 seconds.

[0024] [7] The method for manufacturing aluminum perforated foil according to any one of [1] to [6] above, wherein the processing temperature in the through hole forming process is above 10°C and below 50°C, and the processing time is above 5 seconds and below 120 seconds.

[0025] [8] An aluminum perforated foil having a plurality of through holes extending in the thickness direction.

[0026] The aluminum perforated foil has a thickness of 1 μm or more and 50 μm or less, a tensile strength of 4 N / 10 mm or more and 20 N / 10 mm or less, an average pore size of 1 μm or more and 50 μm or less, and a maximum pore size / average pore size ratio of 4 or less.

[0027] [9] According to the aluminum perforated foil described above [8], the number of holes is 1.0 × 10⁻⁶. 3 pcs / cm 2 Above and 5.0×10 4 pcs / cm 2 Below, the opening ratio is less than 10%, and the air permeability is less than 70 seconds.

[0028]

[10] A current collector for an energy storage device, comprising the aluminum perforated foil described in [8] or [9] above.

[0029] The effects of the invention

[0030] According to the present invention, an aluminum perforated foil suitable for use as a current collector in an energy storage device can be manufactured by a simple method based on alkaline cleaning and subsequent chemical etching. Attached Figure Description

[0031] Figure 1 This is a process illustration of the manufacturing method of the aluminum perforated foil of the present invention. Detailed Implementation

[0032] 1. Manufacturing method of perforated aluminum foil

[0033] This invention relates to a method for manufacturing perforated aluminum foil, characterized in that the perforated aluminum foil has a plurality of through holes extending in the thickness direction, and the manufacturing method includes:

[0034] The alkaline cleaning process involves contacting a first aqueous composition containing 1% by mass and less than 10% by mass of an alkali with the surface of the aluminum foil; and

[0035] In the through-hole forming process, within 20 minutes after the alkaline cleaning process, a second aqueous composition containing more than 1% and less than 30% by mass of halide ions is brought into contact with the surface of the aluminum foil, thereby forming the through-hole in the thickness direction of the aluminum foil.

[0036] Figure 1 This is a schematic diagram illustrating the process of manufacturing the aluminum perforated foil of the present invention. Hereinafter, using... Figure 1 Please provide an explanation.

[0037] like Figure 1As shown in (A), an oxide coating (passivation coating) 2 is usually formed on the surface of aluminum foil 1.

[0038] In the alkaline cleaning process, a first aqueous composition containing 1% by mass and less than 10% by mass of alkali is brought into contact with the surface of the aluminum foil 1 (or the surface of the oxide coating 2). Thus, as... Figure 1 As shown in (B), the oxide coating 2 on the surface of the aluminum foil is partially removed. The oxide coating 2 does not need to be completely removed, only to the extent that halide ions can react with at least a portion of the surface of the aluminum foil in subsequent processes.

[0039] After the alkaline cleaning process, a water washing process can be performed as needed, that is, water can be used to clean the surface of the aluminum foil 1 to remove the alkali adhering to it.

[0040] Within 20 minutes after the alkaline cleaning process, the second aqueous composition containing more than 1% and less than 30% by mass of halide ions is brought into contact with the aluminum foil. Thereby, the halide ions react with the surface of the aluminum foil 1, where the oxide coating 2 has been partially removed, as... Figure 1 As shown in (C), a through hole can be formed that extends through the thickness direction of the aluminum foil 1.

[0041] After the through hole is formed, a water washing process can be carried out as needed, that is, water is used to clean it appropriately to remove halide ions adhering to the surface of the aluminum foil (i.e., aluminum perforated foil) 1.

[0042] As described above, according to the present invention, through-holes can be formed in the thickness direction of the aluminum foil by a simple method of contacting the surface of the aluminum foil with an aqueous composition containing halide ions within 20 minutes after alkaline cleaning. According to a preferred embodiment, the through-holes of the obtained aluminum perforated foil have relatively uniform pore sizes, thus exhibiting an excellent balance between air permeability and tensile strength, making it suitable for use as a current collector for energy storage devices, particularly for lithium-ion capacitors.

[0043] <Alkali Cleaning Process>

[0044] In the alkaline cleaning process, a first aqueous composition containing 1% to 10% by mass of alkali is brought into contact with the surface of the aluminum foil. This process allows for partial removal of the oxide coating (passivation coating) on ​​the surface of the aluminum foil, making it easier to control the subsequent formation of through-holes based on chemical etching.

[0045] Aluminum foil is an alloy plate with aluminum as the main component and trace amounts of different elements. There are no particular limitations as long as it can be used as a current collector in energy storage devices. Examples of these different elements include Fe, Si, Cu, Mg, Zn, Ti, V, Ga, Cr, Zr, B, Mn, Ni, and Li.

[0046] The purity of aluminum is not particularly limited, but is preferably 98% by mass or higher, and can be 98.5% by mass or higher, 99% by mass or higher, 99.3% by mass or higher, 99.5% by mass or higher, or 99.75% by mass or higher. Furthermore, the upper limit is not particularly limited and can be 100% by mass, preferably less than 99.9% by mass, and can be less than 99.8%, less than 99.7%, less than 99.6%, or less than 99.5% by mass.

[0047] As aluminum foil, any type of rigid aluminum foil or flexible aluminum foil can be used. There are no particular limitations on the aluminum foil, but A1000 series and A8000 series are preferred, and it can be A1N30, A8011, A8021 or A8079.

[0048] The thickness of the aluminum foil is preferably 50 μm or less, more preferably 40 μm or less, and even more preferably 25 μm or less. There is no particular limitation on the lower limit of the thickness, but it is generally 1 μm or more. If it falls within the above range, it is suitable for use as a current collector for energy storage devices, particularly for lithium-ion capacitors.

[0049] The first aqueous composition used in the alkaline cleaning process contains more than 1% by mass and less than 10% by mass of alkali.

[0050] As a base, hydroxides of alkali metals such as sodium hydroxide and potassium hydroxide are preferred, or hydroxides of alkaline earth metals such as magnesium hydroxide, calcium hydroxide, strontium hydroxide, and barium hydroxide. Hydroxides of alkali metals are more preferred, and sodium hydroxide is particularly preferred. Two or more bases may be used in combination as needed.

[0051] The alkali content (concentration) in the first aqueous composition is 1% by mass or more and 10% by mass or less, preferably 2.0% by mass or more and 8.0% by mass or less, more preferably 3.0% by mass or more and 7.0% by mass or less, particularly preferably 4.0% by mass or more and 6.0% by mass or less, and even more preferably 4.5% by mass or more and 5.5% by mass or less.

[0052] Furthermore, the range of alkali content contained in the first aqueous composition can be defined as any one of 1.0% by mass, 2.0% by mass, 3.0% by mass, 4.0% by mass, 4.5% by mass, and 5.0% by mass as the lower limit, and any one of 10.0% by mass, 8.0% by mass, 7.0% by mass, 6.0% by mass, and 5.5% by mass as the upper limit.

[0053] The first aqueous composition may contain additives as components other than alkali within the scope of achieving the effects of the present invention. Examples of additives include organic solvents, surfactants, pH adjusters, reducing agents, etc. The concentration of additives that may be contained in the first aqueous composition is preferably 10% by mass or less, more preferably 5.0% by mass or less, further preferably 2.0% by mass or less, and particularly preferably 1.0% by mass or less.

[0054] The first aqueous composition comprises water, particularly ion-exchanged water or ultrapure water. The water content is the balance of the first aqueous composition, preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and may also be 95% by mass or more. The upper limit of the water content is 99% by mass or less, and may be 98% by mass or less, 97% by mass or less, 96% by mass or less, or 95% by mass or less.

[0055] The processing temperature (temperature of the first aqueous composition) in the alkaline cleaning process is preferably 10°C or higher and 50°C or lower, more preferably 20°C or higher and 45°C or lower, and even more preferably 25°C or higher and 40°C or lower. If the temperature of the first aqueous composition is 10°C or higher, cleaning can be performed efficiently in a short time. On the other hand, when the temperature of the first aqueous composition is 50°C or lower, changes in the liquid composition can be suppressed, keeping the alkaline cleaning conditions constant. Furthermore, safe operation is possible.

[0056] There are no particular limitations on the method of contacting the first aqueous composition with the aluminum foil. For example, a wet method (wet etching method) can be used, such as contacting the aluminum foil by dropping (single-sheet spin processing) or spraying (spray processing) of the first aqueous composition, or immersing the aluminum foil in the first aqueous composition.

[0057] The processing time in the alkaline cleaning process is preferably 5 seconds or more and 120 seconds or less, more preferably 8 seconds or more and 100 seconds or less, and even more preferably 10 seconds or more and 60 seconds or less. The processing time can be appropriately determined considering various conditions such as the surface condition of the aluminum foil, the alkali content in the first aqueous composition, the processing temperature, and the contact method. Here, the processing time refers to the time during which the first aqueous composition comes into contact with the surface of the aluminum foil. For example, it is the time during which the aluminum foil is immersed in the first aqueous composition; the time from when the first aqueous composition is sprayed onto the surface of the aluminum foil until the first aqueous composition is removed using water or the like; or the time until the first aqueous composition is removed by contacting the second aqueous composition in the subsequent through-hole forming process.

[0058] <Washing Process>

[0059] After alkaline cleaning, the aluminum foil should preferably be rinsed with water as needed to remove the alkalinity adhering to the surface of the aluminum foil. The water is preferably treated by distillation, ion exchange, filtration, or various adsorption processes to remove metal ions, organic impurities, and particulate matter; pure water or ultrapure water is particularly preferred.

[0060] <Through Hole Formation Process>

[0061] In the through-hole forming process, within 20 minutes after the alkaline cleaning process, a second aqueous composition containing more than 1% and less than 30% by mass of halide ions is brought into contact with the surface of the aluminum foil, thereby forming the through-hole in the thickness direction of the aluminum foil.

[0062] Through-holes can be formed on aluminum foil by contacting a second aqueous composition containing more than 1% and less than 30% by mass of halide ions within 20 minutes after the alkaline cleaning process.

[0063] Here, "within 20 minutes after the alkaline cleaning process" means within 20 minutes after the completion of the alkaline cleaning process, that is, within 20 minutes from the removal of the first aqueous composition from the aluminum foil surface. Preferably, the through-hole formation process is performed within 10 minutes after the alkaline cleaning process, more preferably within 5 minutes, further preferably within 3 minutes, particularly preferably within 2 minutes, or even within 1 minute. As described above, by performing the through-hole formation process in the shortest possible time after the alkaline cleaning process, the treatment can be carried out before a new passivation coating is formed on the aluminum foil surface, thus achieving the effect of more uniformly forming through-holes.

[0064] The second aqueous composition used in the through-hole forming process contains more than 1% by mass and less than 30% by mass of halide ions. By partially removing the oxide coating (passivation coating) through alkaline cleaning, the halide ions react with the surface of the aluminum foil in that portion, thereby forming through-holes in the aluminum foil.

[0065] There is no particular limitation on the type of halide ion, such as fluoride ion, chloride ion, bromide ion, iodide ion. From the point of view of ease of processing and economy, chloride ion is preferred.

[0066] The halogen compound used as the halide ion source in the second aqueous composition is not particularly limited. Examples include alkali metal halides such as sodium halide and potassium halide, alkaline earth metal halides such as calcium halide, ammonium halide, copper halide, and hydrogen halides. From the viewpoint of more effectively and reliably forming through-holes, alkali metal halides or hydrogen halides are preferred, and hydrochloric acid or sodium chloride are more preferred.

[0067] Halogen compounds can be used alone or in combination of two or more.

[0068] The content of halide ions contained in the aqueous composition is 1% by mass or more and 30% by mass or less, preferably 2.0% by mass or more and 25% by mass or less, more preferably 3.0% by mass or more and 20% by mass or less, particularly preferably 5.0% by mass or more and 15% by mass or less, and even more preferably 8% by mass or more and 15% by mass or less.

[0069] Furthermore, the range of halide ion content contained in the second aqueous composition can be defined as any one of 1.0% by mass, 2.0% by mass, 3.0% by mass, 5.0% by mass, and 8% by mass as the lower limit, and any one of 30% by mass, 25% by mass, 20% by mass, 18% by mass, and 15% by mass as the upper limit.

[0070] The second aqueous composition may contain additives as components other than halide ions within the scope of the effects of the present invention. Examples of additives include organic solvents, surfactants, pH adjusters, oxidants, etc. The concentration of additives that may be contained in the second aqueous composition is preferably 10% by mass or less, more preferably 5.0% by mass or less, more preferably 2.0% by mass or less, and particularly preferably 1.0% by mass or less.

[0071] The second aqueous composition comprises water, particularly ion-exchanged water or ultrapure water. The water content is the balance of the second aqueous composition, preferably 70% by mass or more, more preferably 80% by mass or more, further preferably 90% by mass or more, and may also be 95% by mass or more. The upper limit of the water content is 99% by mass or less, and may be 98% by mass or less, 97% by mass or less, 96% by mass or less, or 95% by mass or less.

[0072] The processing temperature (temperature of the second aqueous composition) in the through-hole formation process is preferably 10°C or higher and 50°C or lower, more preferably 15°C or higher and 45°C or lower, and even more preferably 20°C or higher and 40°C or lower. If the temperature of the second aqueous composition is 10°C or higher, through-holes can be formed efficiently in a short time. On the other hand, when the temperature of the second aqueous composition is 50°C or lower, changes in the liquid composition can be suppressed, keeping the etching conditions constant. Furthermore, safe operation is possible.

[0073] There are no particular limitations on the method of contacting the aluminum foil after the alkaline cleaning process with the second aqueous composition. For example, the aluminum foil can be contacted by methods such as dripping (single-sheet spin processing) or spraying (spray processing), or by immersing the aluminum foil in the second aqueous composition, etc., in a wet method (wet etching method).

[0074] The processing time in the through-hole formation process is preferably 5 seconds or more and 120 seconds or less, more preferably 8 seconds or more and 100 seconds or less, and even more preferably 10 seconds or more and 60 seconds or less. The processing time can be appropriately determined considering various conditions such as the surface condition of the aluminum foil, the content of halide ions in the second aqueous composition, the processing temperature, and the contact method. Thus, according to the present invention, it is advantageous that through-holes can be formed even with a relatively short processing time. Here, processing time refers to the time during which the second aqueous composition comes into contact with the surface of the aluminum foil after the alkaline cleaning process. For example, it is the time during which the aluminum foil is immersed in the second aqueous composition, or the time from when the second aqueous composition is sprayed onto the surface of the aluminum foil until the second aqueous composition is removed using water or the like.

[0075] <Washing Process>

[0076] The aluminum foil with through holes (i.e., perforated aluminum foil) is preferably washed with water as needed to remove halide ions adhering to the surface of the aluminum foil. The water is preferably treated by distillation, ion exchange, filtration, or various adsorption processes to remove metal ions, organic impurities, and particulate matter; pure water or ultrapure water is particularly preferred.

[0077] According to the method described above, aluminum perforated foil can be obtained through essentially two-stage chemical treatment, or, if necessary, further moderate cleaning (e.g., water washing). According to the present invention, the processing conditions are stable and the required time is short, thus enabling efficient manufacturing of aluminum perforated foil. Furthermore, according to a preferred embodiment of the present invention, the aperture of the through holes can be uniformly formed, suppressing the reduction in the tensile strength of the resulting aluminum perforated foil. Therefore, by using continuous processes such as roll-to-roll processes to continuously process the aluminum perforated foil, production efficiency can be further improved.

[0078] For example, dripping devices, spraying devices, or impregnation devices for the first and second aqueous compositions can be provided between rolls of aluminum foil. During a roll-to-roll process, while the aluminum foil is unwound and moved from a roll containing untreated aluminum foil, it passes near the aforementioned devices, where the first and second aqueous compositions, and water (optionally used to remove water from each aqueous composition), are supplied. The aluminum foil with through-holes is then wound into a roll. Alternatively, a drying process can be performed before winding the obtained aluminum foil into a roll.

[0079] 2. Aluminum perforated foil

[0080] The aluminum perforated foil of the present invention is characterized in that it has a plurality of through holes extending through the thickness direction.

[0081] The aluminum perforated foil has a thickness of 1 μm or more and 50 μm or less, a tensile strength of 4 N / 10 mm or more and 20 N / 10 mm or less, an average pore size of 1 μm or more and 50 μm or less, and a maximum pore size / average pore size ratio of 4 or less. The aluminum perforated foil of the present invention can be manufactured by the method described in "1. Manufacturing Method of Aluminum Perforated Foil" above.

[0082] The thickness of the aluminum perforated foil is 1 μm or more and 50 μm or less, preferably 40 μm or less, and more preferably 25 μm or less. If it falls within the above range, it is suitable for use as a current collector for energy storage devices, especially for lithium-ion capacitors.

[0083] The fracture strength is 4N / 10mm or more and 20N / 10mm or less, preferably 4.5N / 10mm or more and 15N / 10mm or less, more preferably 5N / 10mm or more and 12N / 10mm or less, and even more preferably 5.5N / 10mm or more and 10N / 10mm or less.

[0084] In addition, the preferred stress is 20 N / mm. 2 Above and 200N / mm 2 The following is more preferably 25 N / mm 2 Above and 150N / mm 2 The following is a further preferred value: 30 N / mm 2 Above and 100N / mm 2 the following.

[0085] In addition, the elongation at break is preferably 0.1% or more and 3% or less, more preferably 0.5% or more and 2% or less, and even more preferably 0.7% or more and 1.5% or less.

[0086] When the breaking strength, stress, and elongation at break of aluminum perforated foil are within the above-mentioned ranges, it can also withstand continuous processes such as roll-to-roll processes, thus improving the production efficiency of aluminum perforated foil.

[0087] The average pore size of the pores in the aluminum perforated foil is 1 μm or more and 50 μm or less, preferably 3 μm or more and 30 μm or less, more preferably 5 μm or more and 25 μm or less, and even more preferably 7 μm or more and 20 μm or less. If the average pore size is within the above range, lithium-ion predoping can be performed efficiently, making it suitable for use as a current collector in lithium-ion capacitors.

[0088] Furthermore, the ratio of maximum aperture to average aperture is 4 or less, preferably 3.8 or less, more preferably 3.6 or less, and even more preferably 3.5 or less. When the ratio of maximum aperture to average aperture is within the above range, the decrease in tensile strength can be suppressed, and it can also withstand continuous processes such as roll-to-roll processes, thus improving the production efficiency of aluminum perforated foil.

[0089] In addition, the number of holes in the aluminum perforated foil is 1.0 × 10⁻⁶. 3 pcs / cm 2 Above and 5.0×10 4 pcs / cm 2 The preferred value is 3.0 × 10⁻⁶. 3 pcs / cm 2 Above and 4.0×10 4 pcs / cm 2 Hereinafter, 5.0 × 10 is preferred. 3 pcs / cm 2 Above and 3.0×10 4 pcs / cm 2 The following is a further preferred value: 7.0 × 10 3 pcs / cm 2 Above and 2.0×10 4 pcs / cm 2 The following applies: When the number of pores is within the above range, a good balance is achieved between tensile strength and predoping efficiency, making it suitable for use as a current collector in lithium-ion capacitors.

[0090] The aperture ratio of the aluminum perforated foil is 10% or less, preferably 5% or less, more preferably 4% or less, and even more preferably 3% or less. It should be noted that the lower limit of the aperture ratio is preferably 0.10% or more, more preferably 0.15% or more, and even more preferably 0.20% or more. When the aperture ratio is within the above range, a good balance is achieved between tensile strength and pre-doped efficiency, making it suitable for use as a current collector in lithium-ion capacitors.

[0091] The air permeability of the aluminum perforated foil is less than 70 seconds, preferably less than 40 seconds, more preferably less than 30 seconds, and even more preferably less than 20 seconds. It should be noted that the lower limit of the air permeability is preferably 0 seconds or more, more preferably 0.5 seconds or more, and even more preferably 1.0 second or more. If the air permeability is within the above range, lithium-ion predoping can be performed efficiently, making it suitable for use as a current collector in lithium-ion capacitors.

[0092] Furthermore, the average spacing between the holes in the aluminum perforated foil is preferably 10 μm or more and 500 μm or less, more preferably 30 μm or more and 250 μm or less, even more preferably 50 μm or more and 150 μm or less, and particularly preferably 60 μm or more and 100 μm or less. When the hole spacing is within the above range, a good balance is achieved between tensile strength and predoping efficiency, making it suitable for use as a current collector in lithium-ion capacitors.

[0093] Furthermore, the surface roughness (arithmetic mean roughness Ra) of the unopened portion of the aluminum perforated foil is preferably 0.01 μm or more and 0.20 μm or less, more preferably 0.02 μm or more and 0.15 μm or less, even more preferably 0.03 μm or more and 0.10 μm or less, and particularly preferably 0.04 μm or more and 0.07 μm or less. When the surface roughness of the unopened portion is within the above range, the decrease in tensile strength can be suppressed, and it can also withstand continuous processes such as roll-to-roll processes, thus improving the production efficiency of the aluminum perforated foil.

[0094] These physical properties can be determined according to the methods described in the examples.

[0095] 3. Current collector for energy storage devices

[0096] The current collector for the energy storage device of the present invention is composed of the aluminum perforated foil described above. The current collector for the energy storage device of the present invention has multiple through holes extending in the thickness direction through the aluminum perforated foil. When used, for example, in a lithium-ion capacitor, it enables efficient pre-doping of lithium ions in a short time, allowing for more uniform dispersion of lithium ions. Therefore, it can handle high capacity requirements and provides an energy storage device that balances high output density and high energy density.

[0097] Example

[0098] The invention will now be described in further detail using examples and comparative examples, but the invention is not limited by these examples.

[0099] The methods for determining each physical property are as follows.

[0100] 1. Analysis of the hole

[0101] The aluminum perforated foils obtained in the examples and comparative examples were observed using an optical microscope (Olympus Corporation, MX63L) with the downward light from the microscope on. The observation range was 3570 × 2230 μm. The obtained microscope images were binarized using image analysis software (Mitani Corporation, WinROOF2018) to calculate the number of holes and the maximum area of ​​the holes within the 3570 × 2230 μm observation range. 2 Total area of ​​pores [μm] 2 ].

[0102] (1) Number of holes

[0103] Number of holes [number / cm] 2 It can be calculated using the following formula.

[0104] [Mathematical Expression 1]

[0105]

[0106] (2) Average pore size

[0107] The average pore size [μm] is calculated using the following formula.

[0108] [Mathematical Expression 2]

[0109]

[0110] (3) Maximum aperture

[0111] The maximum aperture [μm] is calculated using the following formula.

[0112] [Mathematical Expression 3]

[0113]

[0114] (4) Average spacing

[0115] The average spacing [μm] is calculated using the following formula.

[0116] [Mathematical Expression 4]

[0117]

[0118] (5) Opening ratio

[0119] The opening ratio [%] is calculated using the following formula.

[0120] [Mathematical Expression 5]

[0121]

[0122] 2. Measurement of air permeability

[0123] For the aluminum perforated foils obtained in the examples, the air permeability was measured using a digital O-type air permeability tester (manufactured by Asahi Seiko Co., Ltd., REG02-5 / 6-1M·2M) according to the O-type test method based on JIS P 8117-2009. It should be noted that the aluminum perforated foils obtained in the comparative examples all had 0 pores, therefore their air permeability was infinite and could not be measured.

[0124] 3. Measurement of surface roughness of the unopened portion

[0125] For the raw material aluminum foil (reference example) and the aluminum perforated foil obtained in the examples, the arithmetic mean roughness (Ra) according to JIS B 0601-2001 was measured using a laser microscope (KEYENCE Co., Ltd., product name "VK-X250"). The measurement area was the unopened portion. It should be noted that the number of holes in the aluminum perforated foil obtained in the comparative examples was 0, therefore the surface roughness of the unopened portion was the same as that of the reference example (untreated).

[0126] 4. Tensile test

[0127] The raw material aluminum foil (reference example) and the aluminum perforated foil obtained in the examples were cut into 140mm lengths with a width of 10mm. Using a Tensilon universal testing machine (manufactured by A&D Corporation, RTG-1210), the foils were fixed with a chuck spacing of 100mm. The tensile strength [N / 10mm] and stress [N / mm] were measured five times at a tensile speed of 10mm / min. 2 The tensile strength was calculated as follows: elongation at break [%), and the average value was obtained. It should be noted that the number of holes in the aluminum perforated foils obtained in the comparative examples was 0, so the tensile strength was the same as that of the reference example (untreated).

[0128] [Example 1]

[0129] A first aqueous composition was prepared by adding sodium hydroxide to 38.0 kg of pure water to a final amount of 5% by mass (2.0 kg), and a second aqueous composition was prepared by adding hydrochloric acid (as a halide ion) to 26.3 kg of pure water to a final amount of 12% by mass (13.7 kg of 35% hydrochloric acid). Using a roll-to-roll apparatus (manufactured by Jinwa Kogyo Co., Ltd., immersion type) capable of alkaline cleaning → water washing → through-hole formation (etching) → water washing → drying, aluminum foil (AlN30 (soft), thickness 20 μm, width 300 mm, length 10 m) was treated at the temperatures and times specified in Table 1 to obtain aluminum perforated foil. The obtained aluminum perforated foil was subjected to pore analysis, air permeability measurement, surface roughness measurement of unopened portions, and tensile testing.

[0130] [Examples 2 and 3]

[0131] The temperature and time of the roll-to-roll process were changed as described in Table 1, and otherwise the process was performed in the same manner as in Example 1 to obtain an aluminum perforated foil.

[0132] [Examples 4-6]

[0133] The first aqueous composition was prepared by adding sodium hydroxide to 142.5 kg of pure water to a final amount of 5% by mass (7.5 kg). The second aqueous composition was prepared by adding hydrochloric acid (as a halide ion) to 52.6 kg of pure water to a final amount of 12% by mass (27.4 kg of 35% by mass hydrochloric acid). The roll-to-roll device was set to a roll-to-roll device (manufactured by Jinwa Industrial Co., Ltd., top and bottom spray type). The temperature and time of the treatment were changed as described in Table 1. Otherwise, the treatment was carried out in the same manner as in Example 1 to obtain aluminum perforated foil.

[0134] [Examples 7-13]

[0135] The first aqueous composition was prepared by adding sodium hydroxide to 1800g of pure water to a final amount of 5% by mass (100g). The second aqueous composition was prepared by adding hydrochloric acid (as a halide ion) to 1314g of pure water to a final amount of 12% by mass (686g of 35% by mass hydrochloric acid). Without using a roll-to-roll device, the first aqueous composition, the second aqueous composition, and pure water were added to a tank respectively. The mixture was immersed in the tank at the temperature and time specified in Table 1 in the order of alkaline cleaning → water washing → through-hole formation (etching) → water washing. Then, the mixture was allowed to dry thoroughly. The aluminum foil was prepared as specified in Table 1 (thickness 12μm, width 70mm, length 140mm). Except for this, the process was the same as in Example 1 to obtain an aluminum perforated foil.

[0136] [Example 14]

[0137] The first aqueous composition was prepared by adding sodium hydroxide to 180g of pure water to a final amount of 5% by mass (10g). The second aqueous composition was prepared by adding hydrochloric acid (as a halide ion) to 154g of pure water to a final amount of 8% by mass (46g of 35% by mass hydrochloric acid). Without using a roll-to-roll device, the first aqueous composition, the second aqueous composition, and pure water were added to a tank respectively. The aluminum foil (AlN30 (soft), thickness 20μm, width 30mm, length 30mm) was immersed in the aluminum foil at the temperature and time specified in Table 1 in the order of alkaline cleaning → water washing → through-hole formation (etching) → water washing. Then, it was allowed to dry thoroughly to obtain an aluminum perforated foil.

[0138] [Examples 15-20]

[0139] The first aqueous composition, the second aqueous composition, the treatment temperature, and the treatment time were changed to those listed in Table 1. Otherwise, the process was the same as in Example 14 to obtain an aluminum perforated foil.

[0140] [Comparative Example 1]

[0141] The time between treatment 1 (alkaline cleaning) and treatment 2 (through-hole formation) was set to 30 minutes. The first aqueous composition, the second aqueous composition, the treatment temperature, and the time were changed to those recorded in Table 1. Otherwise, the treatment was carried out in the same manner as in Example 14 to obtain an aluminum perforated foil.

[0142] [Comparative Example 2]

[0143] The time between treatment 1 (alkaline cleaning) and treatment 2 (through-hole formation) was set to 30 minutes, and drying was performed. The first aqueous composition, the second aqueous composition, the treatment temperature, and the time were changed to those recorded in Table 1. Otherwise, the treatment was performed in the same manner as in Example 14 to obtain an aluminum perforated foil.

[0144] [Comparative Example 3]

[0145] The second aqueous composition not intended for use in Process 2 was modified to the time specified in Table 1, and otherwise processed in the same manner as in Example 14 to obtain an aluminum perforated foil.

[0146] [Comparative Example 4]

[0147] Instead of using the first aqueous composition for treatment 1, the second aqueous composition for treatment 2 and the treatment time were changed to the times recorded in Table 1. Otherwise, the treatment was carried out in the same manner as in Example 14 to obtain an aluminum perforated foil.

[0148] [Table 1]

[0149]

[0150] [Table 2]

[0151]

[0152] As shown in Tables 1 and 2, according to the method of the present invention, through-holes can be formed by a simple method based on alkaline cleaning and subsequent chemical etching. The resulting aluminum perforated foil has a uniform pore size, excellent air permeability and tensile strength, and is suitable for use as a current collector in energy storage devices.

[0153] Explanation of reference numerals in the attached figures

[0154] 1 Aluminum foil

[0155] 2. Oxidation coating (passivation coating)

[0156] 3 Through holes

Claims

1. A method for manufacturing an aluminum perforated foil, wherein, The aluminum perforated foil has a plurality of through holes extending in the thickness direction, and the manufacturing method includes: The alkaline cleaning process involves contacting a first aqueous composition containing 1% by mass and less than 10% by mass of an alkali with the surface of the aluminum foil; and In the through-hole forming process, within 20 minutes after the alkaline cleaning process, a second aqueous composition containing more than 1% and less than 30% by mass of halide ions is brought into contact with the surface of the aluminum foil, thereby forming the through-hole in the thickness direction of the aluminum foil.

2. The method for manufacturing aluminum perforated foil according to claim 1, wherein, The alkali is a hydroxide of an alkali metal or an alkaline earth metal.

3. The method for manufacturing aluminum perforated foil according to claim 1, wherein, The halide ion is a chloride ion.

4. The method for manufacturing aluminum perforated foil according to claim 1, wherein, The thickness of the aluminum foil is more than 1 μm and less than 50 μm.

5. The method for manufacturing aluminum perforated foil according to claim 1, wherein, The aluminum foil has an aluminum purity of 98% by mass or more and less than 99.9% by mass.

6. The method for manufacturing aluminum perforated foil according to any one of claims 1 to 5, wherein, The alkaline cleaning process involves a processing temperature of 10°C or higher and 50°C or lower, and a processing time of 5 seconds or higher and 120 seconds or lower.

7. The method for manufacturing aluminum perforated foil according to any one of claims 1 to 5, wherein, The processing temperature in the through-hole forming process is above 10°C and below 50°C, and the processing time is above 5 seconds and below 120 seconds.

8. An aluminum perforated foil having a plurality of through holes extending in the thickness direction. The aluminum perforated foil has a thickness of 1 μm or more and 50 μm or less, a tensile strength of 4 N / 10 mm or more and 20 N / 10 mm or less, an average pore size of 1 μm or more and 50 μm or less, and a maximum pore size / average pore size ratio of 4 or less.

9. The aluminum perforated foil according to claim 8, wherein, The number of holes is 1.0 × 10 3 pcs / cm 2 Above and 5.0×10 4 pcs / cm 2 Below, the opening ratio is less than 10%, and the air permeability is less than 70 seconds.

10. A current collector for an energy storage device, comprising the aluminum perforated foil as described in claim 8 or 9.

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