Method for manufacturing perforated aluminum foil

Abstract

According to the present invention, it is possible to provide a method for producing an aluminum perforated foil having a plurality of through-holes penetrating in the thickness direction, the method comprising: a through-hole formation step of bringing an aqueous composition containing 1-30% by mass of halide ions and 0.1-20% by mass of an oxidizing agent into contact with the surface of an aluminum foil, thus, the through hole is formed in the thickness direction of the aluminum foil.

Description

TECHNICAL FIELD

[0001] The present application relates to a manufacturing method of an aluminum porous foil. BACKGROUND

[0002] In recent years, in portable information terminals, portable electronic devices, electric vehicles, hybrid electric vehicles, and stationary power storage systems, the demand for power storage devices, particularly, lithium ion capacitors (LIC), lithium ion secondary batteries (LIB), and electric double layer capacitors (EDLC) has increased. As a current collector for a positive electrode or a negative electrode of these power storage devices, an aluminum porous foil in which through holes for pre-doping lithium ions are formed is known.

[0003] For example, a lithium ion capacitor uses the same activated carbon as an electric double layer capacitor as a positive electrode, and uses the same carbon material as a lithium ion secondary battery as a negative electrode, and can balance high output density and high energy density, but in order to increase capacity, pre-doping of lithium ions needs to be performed efficiently, and a plurality of fine through holes are formed, and thus an aluminum porous foil is formed.

[0004] As a method of forming fine through holes, an etching technique is known.

[0005] For example, in Patent Literature 1, a method of forming through holes on an aluminum foil by electrolytic etching using an aqueous solution containing hydrochloric acid as an electrolyte is described.

[0006] In addition, in Patent Literature 2, a method of forming an aluminum oxide or aluminum hydroxide film on the surface of an aluminum foil, removing the film of a portion where a through hole is desired to be formed by laser processing, and then forming a through hole on the aluminum foil by electrolytic etching using an aqueous solution containing sulfuric acid and nitric acid as an electrolyte is described.

[0007] PRIOR ART DOCUMENTS

[0008] PATENT LITERATURE

[0009] Patent Literature 1: Japanese Patent Application Publication No. 2011-208254

[0010] Patent Literature 2: International Publication No. 2017 / 163913 SUMMARY

[0011] PROBLEMS TO BE SOLVED BY THE INVENTION

[0012] A technology for manufacturing an aluminum porous foil suitable for use as a current collector for a power storage device in a simple method is desired to be developed.

[0013] SOLUTION TO PROBLEM

[0014] The present application relates to a manufacturing method of an aluminum porous foil as shown below.

[0015] <1> A method for manufacturing an aluminum porous foil, wherein the aluminum porous foil has a plurality of through-holes that penetrate in a thickness direction, the method comprising:

[0016] a through-hole forming step of bringing an aqueous composition containing 1 to 30 mass% of halide ions and 0.1 to 20 mass% of an oxidizing agent into contact with a surface of an aluminum foil, thereby forming the through-holes in the thickness direction of the aluminum foil.

[0017] <2> The method for manufacturing an aluminum porous foil according to the above <1>, wherein the halide ions are chloride ions.

[0018] <3> The method for manufacturing an aluminum porous foil according to the above <1>, wherein the oxidizing agent is one or more selected from the group consisting of hydrogen peroxide and nitric acid.

[0019] <4> The method for manufacturing an aluminum porous foil according to the above <1>, wherein the thickness of the aluminum foil is 1 μm or more and 50 μm or less.

[0020] <5> The method for manufacturing an aluminum porous foil according to the above <1>, wherein the aluminum purity of the aluminum foil is 98 mass% or more and less than 99.9 mass%.

[0021] <6> The method for manufacturing an aluminum porous foil according to any one of the above <1> to <5>, wherein the treatment temperature in the through-hole forming step is 10°C or more and 50°C or less, and the treatment time is 10 seconds or more and 150 seconds or less.

[0022] Effects of the Invention

[0023] According to the present invention, an aluminum porous foil suitable for use as a current collector for an electricity storage device can be manufactured by a simple method based on chemical etching. DETAILED DESCRIPTION

[0024] 1. A method for manufacturing an aluminum porous foil

[0025] The present invention is a method for manufacturing an aluminum porous foil, wherein the aluminum porous foil has a plurality of through-holes that penetrate in a thickness direction, the method comprising: a through-hole forming step of bringing an aqueous composition containing 1 to 30 mass% of halide ions and 0.1 to 20 mass% of an oxidizing agent into contact with a surface of an aluminum foil, thereby forming the through-holes in the thickness direction of the aluminum foil.

[0026] According to the present invention, through-holes can be formed on an aluminum foil by a simple method of bringing an aqueous composition containing specific components into contact with a surface of an aluminum foil. According to a preferred embodiment, the uniformity of the pore diameter of the through-holes of the resulting aluminum porous foil is excellent, and the aluminum porous foil can be suitably used as a current collector for an electricity storage device, particularly a lithium-ion capacitor.

[0027] The aluminum foil is an alloy sheet containing aluminum as a main component and a trace amount of different elements, and is not particularly limited as long as it can be used as a current collector for an electricity storage device. As the different elements, for example, Fe, Si, Cu, Mg, Zn, Ti, V, Ga, Cr, Zr, B, Mn, Ni, Li, and the like can be listed.

[0028] The purity of aluminum is not particularly limited, and is preferably 98 mass% or more, and can be 98.5 mass% or more, 99 mass% or more, 99.3 mass% or more, 99.5 mass% or more, or 99.75 mass% or more. In addition, the upper limit value is not particularly limited, and can be 100 mass%, and is preferably less than 99.9 mass%, less than 99.8 mass%, less than 99.7 mass%, less than 99.6 mass%, or less than 99.5 mass%.

[0029] As the aluminum foil, any of a hard aluminum foil and a soft aluminum foil can be used. As the aluminum foil, there is no particular limitation, and A1000 series and A8000 series are preferable, and can be A1N30, A8011, A8021, or A8079.

[0030] The thickness of the aluminum foil is preferably 50 μm or less, more preferably 40 μm or less, and further preferably 25 μm or less. The lower limit value of the thickness is not particularly limited, and is usually 1 μm or more. If it is in the above range, it can be suitably used as a current collector for an electricity storage device, particularly a lithium ion capacitor.

[0031] <Through-hole forming step>

[0032] In the through-hole forming step, an aqueous composition containing 1 to 30 mass% of halide ions and 0.1 to 20 mass% of an oxidizing agent is brought into contact with the surface of the aluminum foil, thereby forming the through-hole in the thickness direction of the aluminum foil.

[0033] The aqueous composition used in the through-hole forming step contains 1 mass% or more and 30 mass% or less of halide ions. The halide ions cause a pitting effect on the passivation film of the aluminum foil, and thus the through-hole can be formed on the aluminum foil.

[0034] The kind of the halide ions is not particularly limited, and can be, for example, fluoride ions, chloride ions, bromide ions, iodide ions, and from the viewpoints of ease of handling and economy, chloride ions are more preferable.

[0035] The halogen compound used as the halide ion source in the aqueous composition is not particularly limited. Examples of the halogen compound include halides of alkali metals such as sodium halide and potassium halide, halides of alkaline earth metals such as calcium halide, ammonium halide, copper halide, and hydrogen halide. Among them, from the viewpoint of more effectively and reliably forming through-holes, halides of alkali metals or hydrogen halide is preferred, and hydrochloric acid or sodium chloride is more preferred.

[0036] The halogen compound can be used alone or in combination of two or more kinds.

[0037] The content of the halide ion 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 23% by mass or less, and particularly preferably 5.0% by mass or more and 20% by mass or less.

[0038] In addition, as the range of the content of the halide ion contained in the aqueous composition, any one of 1.0% by mass, 2.0% by mass, 3.0% by mass, and 5.0% by mass can be used as the lower limit value, and any one of 30% by mass, 25% by mass, 23% by mass, and 20% by mass can be used as the upper limit value.

[0039] The aqueous composition used in the through-hole forming step contains 0.1% by mass or more and 20% by mass or less of an oxidizing agent. It is considered that the oxidizing agent has an effect of promoting the reaction of the halide ion, and it is considered that this contributes to the formation of through-holes on the aluminum foil.

[0040] The kind of the oxidizing agent is not particularly limited, and examples thereof include hydrogen peroxide, nitric acid, persulfate, peroxyacetic acid, ozone, hypochlorite, chlorite, chlorate, perchlorate, chromate, permanganate, and the like. From the viewpoints of ease of handling and economy, hydrogen peroxide and nitric acid are more preferred.

[0041] The oxidizing agent can be used alone or in combination of two or more kinds.

[0042] The content of the oxidizing agent contained in the aqueous composition is 0.1% by mass or more and 20% by mass or less, preferably 0.2% by mass or more and 15% by mass or less, more preferably 0.3% by mass or more and 12% by mass or less, and particularly preferably 0.5% by mass or more and 10% by mass or less.

[0043] In addition, as the range of the content of the oxidizing agent contained in the aqueous composition, any one of 0.1% by mass, 0.2% by mass, 0.3% by mass, and 0.5% by mass can be used as the lower limit value, and any one of 20% by mass, 15% by mass, 12% by mass, and 10% by mass can be used as the upper limit value.

[0044] The aqueous composition optionally contains an additive as a component other than the halide ion and the oxidizing agent within a range where the effects of the present application are exerted. As the additive, an organic solvent, a surfactant, a pH adjuster, and the like can be exemplified. The concentration of the additive optionally contained in the aqueous composition is preferably 10% by mass or less, more preferably 5.0% by mass or less, still more preferably 2.0% by mass or less, and particularly preferably 1.0% by mass or less.

[0045] The aqueous composition contains water, particularly ion-exchanged water or ultrapure water. The content of water is the balance of the aqueous composition, and is preferably 70% by mass or more, more preferably 80% by mass or more, and can be 85% by mass or more. The upper limit of the content of water is 98% by mass or less, and can be 95% by mass or less or 90% by mass or less.

[0046] The treatment temperature (temperature of the aqueous composition) in the through-hole forming step is preferably 10°C or higher and 50°C or lower, more preferably 20°C or higher and 45°C or lower, and further preferably 30°C or higher and 40°C or lower. If the temperature of the aqueous composition is 10°C or higher, the through-hole can be efficiently formed in a short time. On the other hand, if the temperature of the aqueous composition is 50°C or lower, the liquid composition can be inhibited from changing, and the etching conditions can be kept constant. In addition, the work can be safely performed.

[0047] The method of bringing the aqueous composition into contact with the aluminum foil is not particularly limited. A wet method (wet etching method) such as a method of dropping (single piece rotation treatment) or spraying (spray treatment) the aqueous composition, a method of bringing the aluminum foil into contact with the aqueous composition, or a method of immersing the aluminum foil in the aqueous composition can be employed.

[0048] The treatment time in the through-hole forming step is preferably 10 seconds or more and 150 seconds or less, more preferably 30 seconds or more and 140 seconds or less, and further preferably 60 seconds or more and 120 seconds or less. The treatment time can be appropriately determined in consideration of each condition such as the state of the surface of the aluminum foil, the content of the halide ion in the aqueous composition, the treatment temperature, and the contact method. Thus, according to the present application, it is excellent in that the formation of the through-hole can be performed even in a relatively short time. Here, the treatment time means the time of bringing the aqueous composition into contact with the surface of the aluminum foil. For example, it is the time of immersing the aluminum foil in the aqueous composition, or the time from when the aqueous composition is sprayed onto the surface of the aluminum foil to when the aqueous composition is removed with water or the like.

[0049] <Water washing step>

[0050] The aluminum foil having through-holes (i.e., aluminum punched foil) is preferably cleaned as appropriate using water as needed, so as to remove halide ions and oxidizing agents adhering to the surface of the aluminum foil. The water is preferably purified water or ultrapure water, in which metal ions, organic impurities, and particulate matter, etc. have been removed by distillation, ion exchange treatment, filtration treatment, various adsorption treatments, etc.

[0051] According to the above-described method, the aluminum punched foil can be obtained by only substantially one stage of chemical treatment, or further moderate cleaning (e.g., water cleaning) as needed. According to the present application, the conditions of each treatment are stable, and the required time is short, so that the aluminum punched foil can be efficiently manufactured. In addition, according to the preferred embodiment of the present application, the pore diameter of the through-holes can be uniformly formed, and the aluminum punched foil can be continuously processed by using a roll-to-roll process in which a long, coiled current collector is continuously processed by being conveyed along a conveyance line, so that the production efficiency can be further improved.

[0052] For example, a water-based composition can be supplied by providing a dropping device, a spraying device, or an immersion device for the water-based composition between the rolls of the aluminum foil, and by using a roll-to-roll process in which the aluminum foil unwound from a roll of untreated aluminum foil is moved in the vicinity of the above-described device during the unwinding and moving of the aluminum foil, so as to supply the water-based composition, and water for arbitrarily removing each water-based composition, and then the aluminum punched foil having through-holes is wound to obtain a roll. The drying treatment can also be performed before the obtained aluminum punched foil is wound into a roll.

[0053] 2. Aluminum punched foil

[0054] The aluminum punched foil of the present application is characterized by having a plurality of through-holes that pass through in the thickness direction, and the thickness of the aluminum punched foil is preferably 1 μm or more and 50 μm or less. The aluminum punched foil of the present application can be manufactured by the method described in the above-described "Manufacturing method of aluminum punched foil".

[0055] The thickness of the aluminum punched foil is preferably 1 μm or more and 50 μm or less, more preferably 40 μm or less, and particularly preferably 25 μm or less. If the thickness is in the above-described range, the aluminum punched foil can be suitably used as a current collector for an electrical storage device, particularly a lithium ion capacitor.

[0056] The average pore diameter of the holes in the aluminum punched foil is preferably 10 μm or more and 110 μm or less, more preferably 20 μm or more and 100 μm or less, and particularly preferably 23 μm or more and 96 μm or less. If the average pore diameter is in the above-described range, the pre-doping of lithium ions can be efficiently performed, and the aluminum punched foil can be suitably used as a current collector for a lithium ion capacitor.

[0057] The number of holes of the aluminum punched foil is preferably 0.5 x 10 3 cm-2 2 and 10 x 10 3 cm-2 2The following is more preferably 0.7×10 3 pcs / cm 2 Above and 7.0×10 3 pcs / cm 2 The following is particularly preferred: 1.0 × 10 3 pcs / cm 2 Above and 5.0×10 3 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.

[0058] The aperture ratio of the aluminum perforated foil is preferably 26% or less, more preferably 10% or less, and particularly preferably 5.0% or less. It should be noted that the lower limit of the aperture ratio is preferably 0.2% or more, more preferably 0.5% or more, and even more preferably 0.7% 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.

[0059] The average spacing between the holes in the aluminum perforated foil is preferably 100 μm or more and 350 μm or less, more preferably 120 μm or more and 320 μm or less, and particularly preferably 140 μm or more and 310 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.

[0060] These physical properties can be determined according to the methods described in the examples.

[0061] 3. Current collector for energy storage devices

[0062] 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 provide an energy storage device capable of handling high capacity while maintaining high output density and high energy density.

[0063] Example

[0064] The following examples and comparative examples illustrate the features of the present invention in more detail. However, the scope of the present invention is not limited to the following examples.

[0065] <Analysis of the Hole>

[0066] For the aluminum open-cell foils obtained in the examples and comparative examples, an optical microscope (manufactured by Olympus Corporation, MX63L) was used to perform observation in a state in which light from below attached to the device was turned on. The observation range was 3570 x 2230 μm. An image analysis software (manufactured by San-Ei Gen F.F.I., Ltd., WinROOF 2018) was used to binarize the obtained microscope image, and the number of cells [cells / cm2] in the observation range of 3570 x 2230 μm, the average cell diameter [μm], the average pitch [μm], and the opening ratio [%] were calculated. 2 ] in the observation range of 3570 x 2230 μm, the average cell diameter [μm], the average pitch [μm], and the opening ratio [%] were calculated.

[0067] (Number of cells)

[0068] The number of cells [cells / cm2] was calculated by the following equation. 2

[0069] [Mathematical formula 1]

[0070]

[0071] (Average cell diameter)

[0072] The average cell diameter [μm] was calculated by the following equation.

[0073] [Mathematical formula 2]

[0074]

[0075] (Average pitch)

[0076] The average pitch [μm] was calculated by the following equation.

[0077] [Mathematical formula 3]

[0078]

[0079] (Opening ratio)

[0080] The opening ratio [%] was calculated by the following equation.

[0081] [Mathematical formula 4]

[0082]

[0083] (Example 1)

[0084] ​Hydrogen peroxide (as an oxidizing agent) in an amount of 35 mass% of hydrogen peroxide 2.8 g eventually becoming 0.5 mass% and hydrochloric acid (as a halide ion) in an amount of 35 mass% of hydrochloric acid 69 g eventually becoming 12 mass% were added to 128 g of pure water, respectively, to prepare an etching liquid (aqueous composition). In the obtained etching liquid, an aluminum foil (A1N30 (soft), thickness 20 μm, width 30 mm, length 30 mm) was immersed at the temperature and for the time described in Table 1 below to perform etching treatment, and then, after water washing, it was sufficiently dried to obtain an aluminum porous foil. The obtained aluminum porous foil was subjected to analysis of the pores. The results of the number of pores [pieces / cm 2 ], average pore diameter [μm], average pitch [μm], and opening ratio [%] are shown in Table 1 below.

[0085] (Examples 2 to 8)

[0086] The etching liquid used, the temperature of the treatment, and the time of the treatment were changed as described in Table 1 below, respectively, and otherwise, the same as in Example 1, an aluminum porous foil was obtained. The results of the number of pores [pieces / cm 2 ], average pore diameter [μm], average pitch [μm], and opening ratio [%] are shown in Table 1 below.

[0087] (Example 9)

[0088] Hydrochloric acid (as a halide ion) in an amount of 35 mass% of hydrochloric acid 69 g eventually becoming 12 mass% and nitric acid (as an oxidizing agent) in an amount of 60 mass% of nitric acid 33 g eventually becoming 10 mass% were added to 98 g of pure water, respectively, to prepare an etching liquid (aqueous composition). Using the obtained etching liquid, etching treatment was performed at the temperature and for the time described in Table 1 below, and otherwise, the same as in Example 1, an aluminum porous foil was obtained. The results of the number of pores [pieces / cm 2 ], average pore diameter [μm], average pitch [μm], and opening ratio [%] are shown in Table 1 below.

[0089] (Comparative Example 1)

[0090] An etching liquid was prepared without using an oxidizing agent, and the temperature of the treatment and the time of the treatment were changed as described in Table 1 below, and otherwise, the same as in Example 1, an aluminum porous foil was obtained. The number of pores of the obtained aluminum porous foil was zero.

[0091] [Table 1]

[0092]

Claims

1. A method of manufacturing an aluminum aperture foil, wherein, The aluminum porous foil has a plurality of through-holes that pass through in a thickness direction, and the manufacturing method includes: A through-hole forming step brings an aqueous composition containing 1 to 30 mass% of halide ions and 0.1 to 20 mass% of an oxidizing agent into contact with a surface of an aluminum foil, thereby forming the through-holes in a thickness direction of the aluminum foil.

2. The method of manufacturing an aluminum punched foil according to claim 1, wherein, The halide ions are chloride ions.

3. The method of manufacturing an aluminum punched foil according to claim 1, wherein, The oxidizing agent is one or more selected from the group consisting of hydrogen peroxide and nitric acid.

4. The method of manufacturing an aluminum punched foil according to claim 1, wherein, The thickness of the aluminum foil is 1 μm or more and 50 μm or less.

5. The method of manufacturing an aluminum punched foil according to claim 1, wherein, The purity of aluminum of the aluminum foil is 98 mass% or more and less than 99.9 mass%.

6. The method of manufacturing an aluminum punched foil according to any one of claims 1 to 5, wherein The processing temperature in the through-hole forming step is 10°C or more and 50°C or less, and the processing time is 10 seconds or more and 150 seconds or less.

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