JP2019137902A - Aluminum foil - Google Patents

Abstract

To provide an aluminum foil having softness (flexibility) suitable for use of a current collector with a degree that can wind and manufacture a coil-like aluminum foil.SOLUTION: An aluminum foil has a thickness of 20 μm or lower and is composed of an aluminum having an AI content of 97 mass% or more. A hydrogen detected from the aluminum foil is 30 ppm or more and 200 ppm or less in a mass ratio. Preferably, the hydrogen detected from the aluminum foil is 170 ppm or less in the mass ratio.SELECTED DRAWING: None

Description

  The present invention relates to an aluminum foil, and more particularly to an aluminum foil produced by using an electrolytic deposition method suitable for a current collector application.

  In recent years, progress has been made in products and technologies that use power storage devices having a large energy density, such as small mobile tools such as mobile phones and laptop computers, hybrid vehicles, and solar power generation. For this reason, energy storage devices such as lithium ion secondary batteries and supercapacitors (electrical double layer capacitors, redox capacitors, lithium ion capacitors, etc.) are further miniaturized in addition to higher energy density (higher capacity and higher output). Improvements in safety and reliability (lifetime) are required. As a measure for satisfying the demand for such an electricity storage device, it is conceivable to reduce the thickness of the sheet-like current collector constituting the electrode of the electricity storage device. For example, in the case of a positive electrode, an aluminum foil is generally used for a current collector (positive electrode current collector) carrying an active material.

  The thickness of the above-described current collector aluminum foil is currently formed to be about 15 to 20 μm by rolling. It is considered that by forming this thickness thinner, the above-described requirements for the electricity storage device can be satisfied. However, the thickness that can be produced by rolling on an industrial production scale of aluminum foil is currently 20 μm or more when formed on a rough surface suitable for supporting an active material, and a smooth surface that is disadvantageous for supporting an active material. Even when formed, it is said to be 12 μm or more. Therefore, an electrolytic deposition method (electrolytic method) in which an aluminum source is used as an anode and aluminum is electrodeposited on the surface of the cathode using an electrolytic aluminum plating solution (electrolytic solution) is a focus of attention as a method for producing an aluminum foil in place of rolling. Has been. According to such an electrolysis method, an aluminum foil (electrolytic aluminum foil) can be produced by peeling off an aluminum coating formed by electrodeposition on the surface of a cathode substrate (for example, Patent Document 1). In order to enable continuous production of electrolytic aluminum foil, an electrolytic aluminum foil production apparatus using a drum-shaped cathode base material (cathode drum) having a circular cross section has been proposed (for example, Patent Document 2).

International Publication No. 2011/001932 JP 2012-246561 A

  When an electrolytic aluminum foil manufacturing apparatus having a cathode drum as disclosed in Patent Document 2 is used, the electrolytic aluminum foil is continuously wound up to collect the electrolytic aluminum foil into a coiled form. be able to. However, the electrolytic aluminum foil or coiled electrolytic aluminum foil that is being wound may have microcracks (hair cracks) or cracks due to the action of tensile, bending, or torsional forces, and sometimes breaks. May occur. Therefore, when the electrolytic aluminum foil is wound, it is required to be an electrolytic aluminum foil having flexibility (flexibility) enough to withstand the tensile force, bending force, torsional force, and the like.

  INDUSTRIAL APPLICABILITY The present invention enables an electrolytic aluminum foil having a flexibility (flexibility) suitable for a current collector application that enables coiled winding of the electrolytic aluminum foil and enables production of the coiled electrolytic aluminum foil ( Hereinafter, the object is simply to provide “aluminum foil”.

  In the electrolysis method using an electroplating aluminum solution, the flexibility of aluminum foil manufactured under various conditions was examined, and hydrogen (H) unavoidably contained in the aluminum foil in the electrolysis method is the flexibility of the aluminum foil. The present invention has been found and the present invention has been conceived.

  That is, the aluminum foil of the present invention is an aluminum foil having a thickness of 20 μm or less and 97 mass% or more made of aluminum, and the hydrogen detected from the aluminum foil is 30 ppm or more and 200 ppm or less by mass ratio.

  Hydrogen detected from the aluminum foil is preferably 170 ppm or less in terms of mass ratio.

  ADVANTAGE OF THE INVENTION According to this invention, the aluminum foil which has the softness | flexibility (flexibility) suitable for the electrical power collector use of the grade which enables coiled winding of aluminum foil and manufacture of coiled aluminum foil is provided. can do.

It is an example of the electrolytic aluminum foil manufacturing apparatus, and is a figure which shows the internal structure typically. It is a figure (graph) which shows the relationship between the amount of hydrogen contained in aluminum foil, and the flexibility of aluminum foil. It is a figure (graph) which shows the relationship between the addition amount of the additive of a plating solution, and the amount of hydrogen contained in aluminum foil. It is a figure (graph) which shows the relationship between the addition amount of the additive of a plating solution, and the flexibility of aluminum foil. It is a figure (graph) which shows the relationship between the temperature of a plating solution, and the amount of hydrogen contained in aluminum foil. It is a figure (graph) which shows the relationship between the temperature of a plating solution, and the flexibility of aluminum foil.

  The aluminum foil (electrolytic aluminum foil) of the present invention is an aluminum foil having a thickness of 20 μm or less and 97% by mass or more of aluminum (Al), and hydrogen (H) detected from the aluminum foil has a mass of The ratio is 30 ppm or more and 200 ppm or less. Hereinafter, although the example of embodiment of the aluminum foil (electrolytic aluminum foil) of this invention is demonstrated, this invention is not limited to these illustrations, is shown by the claim and is equivalent to a claim All changes within the meaning and scope of are intended to be included.

An important feature of the present invention is the amount of hydrogen (H content) detected from the aluminum foil.
In embodiment of the aluminum foil of this invention, hydrogen (H) detected from aluminum foil is 30 ppm or more and 200 ppm or less by mass ratio. The H content in the aluminum foil is a temperature-programmed desorption gas analysis (TDS analysis) that determines the spectral intensity (ionic strength) of the gas desorbed in the process of heating the aluminum foil in a vacuum atmosphere and quantifies the amount of desorbed gas. ) To obtain a numerical value (ppm) based on the quantitative value obtained from the half-value width of the spectrum intensity obtained in (1). When following the above, it has been confirmed by various trials that the aluminum foil has preferable flexibility when the H content detected from the aluminum foil is 200 ppm or less. This point will be described in detail later.

  When H detected from the aluminum foil is 200 ppm or less by mass ratio, the aluminum foil is less likely to become brittle, and therefore, preferable flexibility can be obtained. As the H content detected from the aluminum foil is smaller, the embrittlement of the aluminum foil is suppressed, and the flexibility of the aluminum foil becomes more preferable. Therefore, H detected from the aluminum foil as an aluminum foil, particularly as an aluminum foil suitable for current collector applications, is preferably 170 ppm or less, more preferably 160 ppm or less, and even more preferably 150 ppm or less. It has been confirmed that the total of carbon (C) and other elements described later also decreases as H detected from the aluminum foil decreases.

  On the other hand, in the embodiment of the aluminum foil of the present invention, H detected from the aluminum foil is 30 ppm or more by mass ratio. From the viewpoint of enhancing the flexibility of the aluminum foil, it is considered that H contained in the aluminum foil is preferably as small as possible. However, the aluminum foil formed by the electrolytic method using the electroaluminum plating solution contains H of 10 ppm or more by mass ratio. Therefore, when forming an aluminum foil by an electrolysis method, it must be permitted that H of 10 ppm or more is inevitably contained in the aluminum foil in a mass ratio. Moreover, when producing an aluminum foil by practical mass production equipment using an electrolytic method, it must be allowed that the aluminum foil inevitably contains about 30 ppm of H exceeding 10 ppm by mass. . From such a viewpoint, in the embodiment in which the mass production facility for aluminum foil of the present invention is used, H detected from the aluminum foil is considered to be 30 ppm or more by mass ratio.

In the embodiment of the aluminum foil of the present invention, the aluminum foil has a thickness of 20 μm or less as an aluminum foil particularly suitable for a current collector application. In addition, the thickness of the aluminum foil is an average value of three measured values obtained by measuring an arbitrary region located about 5 mm inside from an arbitrary end of the aluminum foil at an arbitrary three locations per 1 cm ² using a micrometer. Based on the numerical value (μm). Specifically, it is generally commercially available at any three locations within an area of about 1 cm ^{2 in} an area of about 5 mm from the arbitrary edge in the width direction of the aluminum foil extending in the longitudinal direction toward the inner side in the width direction. The thickness of the aluminum foil is measured using a micrometer, the average value of the three measured values obtained is obtained, and the average value can be used as the thickness (average thickness) of the aluminum foil.

When an aluminum foil is produced by an electrolytic method, the strength of the aluminum coating is increased when the thickness of the aluminum coating is large. Therefore, it is convenient to peel the aluminum coating from the cathode substrate. For example, the 0.2% proof stress of the electrolytic aluminum foil, about when the thickness is about 65N / mm ² at about 10 [mu] m, about 110N / mm ² and thickness when the thickness is about 20μm of about 25 [mu] m 125N / It has been confirmed is of a mm ^2. However, as an aluminum foil for a current collector that can satisfy the above-described requirements for an electricity storage device, for example, when applied to a positive electrode current collector, an aluminum foil having a smaller thickness is required. When applying the current collector aluminum foil to an electricity storage device or the like, the thickness of the aluminum foil currently required is 15 μm or more and 20 μm or less. In the future, as the performance and size of power storage devices and the like increase, the demand for thinner aluminum foil for current collectors will increase. Therefore, the upper limit of the thickness of the aluminum foil for current collectors is 18 μm, 16 μm, and 14 μm. Thus, the smaller one is preferable. Note that the lower limit of the thickness of the current collector aluminum foil is desired to be thinner, so it varies depending on the required mechanical strength, flexibility, etc., but is 12 μm, 10 μm, 8 μm, 6 μm, 4 μm. Furthermore, the smaller one is preferable like 2 micrometers. As a result, an appropriate range can be selected for the thickness of the current collector aluminum foil.

  In the embodiment of the aluminum foil of the present invention, 97% by mass or more of the aluminum foil is composed of Al. The Al content in the aluminum foil is a numerical value (mass%) based on a quantitative value obtained by a fluorescent X-ray analysis method of irradiating the surface in the thickness direction of the aluminum foil. When the Al content of the aluminum foil is 97% by mass or more, since the electrical resistance such as the volume resistivity of the aluminum foil becomes small, the aluminum foil for a current collector that can satisfy the requirements for the above-described power storage device, for example, By applying it as a positive electrode current collector, it is possible to improve the power storage efficiency and heat dissipation. 97 mass% or more of the aluminum foil is composed of Al, but less than 3 mass% (excluding H) other than Al is caused by an additive element or is an unavoidable impurity. In addition, the more Al that constitutes the aluminum foil, the higher the ductility of the aluminum foil and the more preferable the flexibility of the aluminum foil. Therefore, as an aluminum foil, particularly as an aluminum foil suitable for current collector applications, Al constituting the aluminum foil is preferably 98% by mass or more, more preferably 99% by mass or more, and still more preferably 99.5% by mass. That's it.

  Next, an example of a method for producing an aluminum foil (electrolytic aluminum foil) will be described using an example of an electrolytic aluminum foil production apparatus using a cathode drum. In addition, although it is desirable to manufacture the aluminum foil of this invention with the electrolytic aluminum foil manufacturing apparatus and aluminum foil manufacturing method which are illustrated here, it is not limited to the aluminum foil manufactured by this.

  The internal structure of an example of an electrolytic aluminum foil manufacturing apparatus is shown in FIG. An electrolytic aluminum foil production apparatus 1 (foil production apparatus 1) shown in FIG. 1 includes a lid 1a, an electrolytic cell 1b, a cathode drum 1c, an anode member 1d, a guide roll 1e, a foil outlet 1f, a plating solution circulation device 1j, and a ceiling. 1k, stirring flow guide 1m, stirring blade 1n, and DC power supply (not shown). The cathode drum 1c has an outer peripheral surface having an electrodeposition region for electrodepositing an aluminum coating. The outer peripheral surface of the cathode drum 1c is made of titanium. The cathode drum 1c is previously provided with a lead material (not shown) for peeling the aluminum film deposited on the electrodeposition region. The plating solution L is stored in the electrolytic cell 1b. The electrodeposition region of the cathode drum 1c is immersed in the plating solution L. The anode member 1d is made of Al. Al constituting the anode member 1d is preferably 99.0% by mass or more of Al. The electrodeposition region of the cathode drum 1c and the anode member 1d are disposed so as to face each other in the plating solution L. The electrodeposition region of the cathode drum 1c and the anode member 1d are connected to a DC power source. The foil making apparatus 1 uses a means for injecting a heated gas G (for example, an inert gas such as nitrogen gas or argon gas) from the gas supply port 1g, and the cathode drum 1c immediately before entering the plating solution L. It is possible to provide a heating means capable of heating the electrodeposition region to a temperature at which plating can be performed (about the temperature of the plating solution L).

When an electrolytic aluminum foil (aluminum foil F) is manufactured using the foil manufacturing apparatus 1, the electrodeposition region of the cathode drum 1c and the electrode material of the cathode drum 1c are partly immersed in the plating solution L. energized in a region and the anode member 1d, it is controlled to be a predetermined value in the range of current density, for example, 50 mA / cm ² or more ~600mA / cm ² or less. By the energization, aluminum is electrodeposited on the electrodeposition region of the cathode drum 1c immersed in the plating solution L and a part of the lead material. The plating solution L can be heated and held at a temperature at which plating can be performed, for example, by using means for heating with a heater 1i connected to a heater power source 1h. The plating solution L flows uniformly between the cathode drum 1c and the anode member 1d while being stirred by the stirring flow guide 1m and the rotating stirring blade 1n. The homogeneous flow of the plating solution L can make the aluminum film which is deposited and grown on the electrodeposition region of the cathode drum 1c uniform.

  When energization is continued, Al is further electrodeposited and grows, and an aluminum film having a predetermined thickness corresponding to the plating process conditions is formed in the electrodeposition region of the cathode drum 1c. When the cathode drum 1c rotates at a constant speed (for example, 0.02 rpm or more and 0.3 rpm or less) so as to synchronize with the film formation rate of the aluminum film, electrodeposition of a new cathode drum 1c that has entered the plating solution L Al is electrodeposited on the region and grows, and an aluminum film having a predetermined thickness corresponding to the plating conditions is continuously formed. On the other hand, the electrodeposition region of the cathode drum 1c on which the aluminum coating is formed rises from the surface of the plating solution L due to the rotation of the cathode drum 1c, and continuously enters the atmosphere of the electrolytic cell 1b. . After the aluminum film having a predetermined length is formed, the lead material is guided to the guide roll 1e, drawn out from the foil drawing port 1f, and taken up by a winding device (not shown). When the lead material starts to be wound, the end portion of the aluminum film connected to the lead material is drawn, and the aluminum film starts to peel from the electrodeposition region of the cathode drum 1c. Thereafter, the formation of the aluminum film in the electrodeposition region of the cathode drum 1c, the peeling of the aluminum film from the electrodeposition region of the cathode drum 1c, and the winding of the aluminum foil F obtained by the peeling of the aluminum film are continuously performed. Thus, the aluminum foil F can be continuously produced. When the aluminum foil is produced one by one using a cathode base material such as a flat plate without using the cathode drum, the current density, the energization time, etc. can be controlled so that the aluminum coating has a predetermined thickness. .

  The anode member (for example, anode member 1d) serving as an anode for supplying Al ions into the plating solution is preferably a member made of high purity (for example, 99% by mass or more) Al. The electrodeposition region (for example, the electrodeposition region of the cathode drum 1c) for electrodepositing the aluminum coating is, for example, pure titanium (Ti), titanium alloy (Ti alloy), pure aluminum (Al), aluminum alloy (after Al). It can be manufactured using a flat plate or a cylindrical shape having a flat or outer peripheral surface made of gold, pure nickel (Ni), nickel alloy (Ni alloy), stainless steel (SUS), or the like. . For example, the electrodeposition region of the cathode drum 1c is preferably made of a pure titanium having a thermal conductivity of about 17 W / mK and an outer diameter of 300 mm or more and 3000 mm or less. The surface of the electrodeposition region is preferably as smooth as possible so that the aluminum coating can be smoothly peeled, and more preferably an oxide layer (for example, an anode) formed to have a predetermined thickness and surface roughness. It is a surface having an oxide layer by oxidation treatment.

  The aluminum foil F drawn out of the apparatus (in the foil production apparatus 1 shown in FIG. 1, outside the foil outlet 1 f of the electrolytic cell 1 b) is sufficient to remove the plating solution L adhering to the surface. Washed (for example, with water). The environment in which at least the plating treatment and the cleaning are performed is to suppress the deterioration of the plating solution L to extend the life of the plating solution L, and to suppress the reaction of the plating solution adhering to the aluminum foil F. From the viewpoint of preventing the coloring failure of the aluminum foil, a non-oxidizing dry atmosphere is obtained by means such as introducing nitrogen gas having a dew point of −40 ° C. or lower to increase the pressure inside from the atmospheric pressure. It is desirable to keep it.

  After the washing, the aluminum foil is sufficiently dried using, for example, warm air or far infrared rays. If the moisture remaining on the surface of the aluminum foil is not sufficiently removed, unevenness occurs in the oxide film (including the natural oxide film) formed on the surface of the aluminum foil. Such an aluminum foil, when used as a current collector aluminum foil capable of satisfying the above-mentioned requirements for an electricity storage device, for example, for a positive electrode current collector, has characteristics of the electricity storage device due to destabilization of electrochemical behavior and the like. There is a risk of adverse effects.

  After the drying, the aluminum foil is heat-treated as necessary. The heat treatment of the aluminum foil is performed using a batch furnace or a continuous furnace or simultaneously with the drying. The heat treatment of the aluminum foil is performed in an environment such as an air atmosphere, a reduced pressure atmosphere, or a non-oxidizing atmosphere into which an inert gas such as argon gas or nitrogen gas is introduced. The heat treatment of the aluminum foil is, for example, in the range of 80 ° C. to 550 ° C. and 2 minutes to 180 minutes, specifically 200 ° C. × 10 minutes, 200 ° C. × 180 minutes, 300 ° C. × 90 minutes or 460 ° C. × 10 It is carried out under various holding conditions considered to be suitable for the properties of the aluminum foil, such as the minute. If the holding temperature is less than 80 ° C. or the holding time is less than 2 minutes, the heat treatment effect may be insufficient. When the holding temperature exceeds 550 ° C., the aluminum foil is too close to the melting point of Al (about 660 ° C.), and the aluminum foil may be excessively softened. If the holding time exceeds 120 minutes, the productivity of the aluminum foil may be adversely affected. From such a viewpoint, the holding temperature is preferably 100 ° C. or higher and 460 ° C. or lower, more preferably 200 ° C. or higher and 350 ° C. or lower. Similarly, the holding time is preferably 20 minutes or longer and 90 minutes or shorter. Such heat treatment not only solves the problem of poor drying of the aluminum foil, but also contributes to the removal of strain and the reduction of the H content of the aluminum foil. Therefore, the aluminum foil has more favorable flexibility with improved mechanical properties such as tensile strength.

  When an electrolytic aluminum foil (aluminum foil F) is continuously produced using the foil making apparatus 1 described above, the aluminum coating is peeled off from the electrodeposition region of the cathode drum 1c in a sound and easy manner. It is preferable that the obtained aluminum foil F is wound up soundly and easily. In such a case, the hydrogen (H) detected from the aluminum foil that has been washed and dried after the plating solution is detected, and the hydrogen (H) that is detected from the aluminum foil that has been further heat-treated is 200 ppm or less by mass ratio. Good. Such an aluminum foil has favorable flexibility (the aluminum coating is considered to have the same flexibility). Therefore, sound and easy peeling of the aluminum film and healthy and easy coiling of the peeled aluminum foil are possible, and sound and easy manufacture of the coiled aluminum foil is possible.

  The plating solution used in the study of the aluminum foil of the present invention is an electrolytic aluminum plating solution containing at least a dialkyl sulfone as a solvent, an aluminum halide as a solute, and a nitrogen-containing compound as an additive. This plating solution contains Al ions derived from aluminum halide at a predetermined concentration. The aluminum foil F formed using this plating solution is composed of 97 mass% or more of Al. This Al is brought from the anode member 1d by energization, and is deposited on the electrodeposition region of the cathode drum 1c through a plating solution containing Al ions at a predetermined concentration. In addition, as long as electrodeposition of Al from the solution is possible, not only the plating solution described above, even if the type of solution is different, the H content detected from the aluminum foil described above and the aluminum foil The relationship with flexibility is considered to hold.

  Examples of the plating solution used for producing the aluminum foil of the present invention include a dialkyl sulfone as a nonaqueous solvent, an aluminum halide as a solute for containing aluminum ions at a predetermined concentration, and a nitrogen-containing compound as an additive. What contains at least is mentioned. If such a plating solution is used, even if a large current is applied to increase the film formation rate, a stable electroaluminum plating process can be performed. As a result, it is possible to easily produce a high-purity aluminum foil suitable for a current collector application in which 97% by mass or more is made of Al. Such a plating solution does not contain an organic solvent such as benzene or toluene. As a result, the plating solution adhering to the aluminum foil immediately after peeling from the cathode drum 1c can be easily removed by washing with water, and the waste liquid treatment can be performed with relatively simple equipment.

Examples of the dialkyl sulfone as a solvent in the plating solution include straight-chain and branched alkyl groups having 1 to 6 carbon atoms such as dimethyl sulfone, diethyl sulfone, dipropyl sulfone, dihexyl sulfone, and methyl ethyl sulfone. The thing of the shape is mentioned. From the viewpoint of good electrical conductivity and availability, it is preferable to employ dimethyl sulfone. Examples of the aluminum halide that is a solute in the plating solution include aluminum chloride and aluminum bromide. From the viewpoint of reducing the amount of water in the plating solution, which is a factor that inhibits electrodeposition of aluminum, as much as possible, an anhydrous aluminum halide (for example, anhydrous aluminum chloride) is preferable. Examples of the nitrogen-containing compound that is an additive in the plating solution include ammonium halide, primary amine hydrogen halide salt, secondary amine hydrogen halide salt, tertiary amine hydrogen halide salt, and When the same or different alkyl groups are represented by R ^{1 to} R ⁴ and the counter anion for the quaternary ammonium cation is represented by X, a quaternary ammonium salt represented by the general formula: R ¹ R ² R ³ R ⁴ N · X, etc. One or more can be selected. A plating solution containing an appropriate amount of a nitrogen-containing compound in a solution composed of a dialkyl sulfone (nonaqueous solvent) and an aluminum halide (solute) is preferred, and more preferably monomethylamine hydrochloride, dimethylamine hydrochloride, trimethylamine (TMA) hydrochloric acid. It is a plating solution containing any one of salts and ammonium chloride (NH ₄ Cl) (one or more if necessary). Nitrogen-containing compounds such as the above-mentioned TMA hydrochloride and NH ₄ Cl can sufficiently suppress the embrittlement of the aluminum foil and more preferably increase the flexibility of the aluminum foil.

Examples of the ammonium halide that is an option for the nitrogen-containing compound include ammonium chloride and ammonium bromide. In the primary amine hydrohalide salt, secondary amine hydrohalide salt and tertiary amine hydrohalide salt which are the options of the above nitrogen-containing compounds, examples of the primary amine to tertiary amine include, for example, methyl Linear or branched alkyl groups having 1 to 6 carbon atoms such as amine, dimethylamine, trimethylamine, ethylamine, diethylamine, triethylamine, propylamine, dipropylamine, tripropylamine, hexylamine and methylethylamine. Things. Examples of the hydrogen halide in the hydrogen halide salt include hydrogen chloride and hydrogen bromide. In the quaternary ammonium salt represented by the general formula: R ¹ R ² R ³ R ⁴ N · X, which is an option of the nitrogen-containing compound, examples of the alkyl group represented by R ^{1 to} R ⁴ include a methyl group, A linear or branched one having 1 to 6 carbon atoms such as an ethyl group, a propyl group and a hexyl group can be mentioned. As said X, BF4-, PF6-, etc. other than halide ions, such as a chlorine ion, a bromine ion, and an iodine ion, are mentioned, for example. Specific examples of the quaternary ammonium salt include tetramethylammonium chloride, tetramethylammonium bromide, tetramethylammonium iodide, and tetraethylammonium tetrafluoride.

A plating solution containing at least a dialkyl sulfone (such as dimethyl sulfone), an aluminum halide (such as anhydrous aluminum chloride) and a nitrogen-containing compound (such as TMA hydrochloride or NH ₄ Cl) has an aluminum halide content per 10 moles of dialkyl sulfone. 1.0 mol to 4.8 mol is preferably compounded, more preferably 1.5 mol to 4.2 mol. If the amount of aluminum halide compounded is less than 1.5 moles relative to 10 moles of dialkyl sulfone, the aluminum foil may turn black (a phenomenon called burning) and film formation efficiency will decrease. There is a fear. If the blending amount of aluminum halide exceeds 4.8 moles with respect to 10 moles of dialkyl sulfone, the resistance (liquid resistance) of the plating solution becomes excessively large and heat is generated, and the plating solution may be decomposed by heat. There is.

  In the plating solution, the nitrogen-containing compound is preferably added in an amount exceeding 0.05 mol (for example, 0.06 mol or more), more preferably 0.07 mol, per 10 mol of the dialkyl sulfone. As mentioned above, More preferably, it is 0.08 mol or more. When the compounding amount of the nitrogen-containing compound is 0.05 mol or less with respect to 10 mol of the dialkyl sulfone, the effect as an additive of the nitrogen-containing compound (the effect of improving the flexibility by suppressing the embrittlement of the aluminum foil, the plating solution There is a possibility that the effect of improving the film formation speed by increasing the electric conductivity of the film to increase the current density may not be obtained. The amount of the nitrogen-containing compound is increased, and if it exceeds 2.0 moles with respect to 10 moles of dialkyl sulfone, Al may not be properly electrodeposited. Therefore, the amount is preferably 2.0 moles or less. Preferably it is 1.5 mol or less.

  In the electroaluminum plating treatment, as will be described later, it is recognized that the hydrogen amount (H content) detected from the aluminum foil is reduced by lowering the temperature (solution temperature) of the electroaluminum plating solution. Therefore, by controlling the liquid temperature below a predetermined value, the aluminum foil may have a preferable flexibility. For example, there is a possibility that the H content of the aluminum foil may be 200 ppm or less by mass ratio by a manufacturing method in which the liquid temperature can be electroaluminum-plated and kept at about 110 ° C. to 120 ° C. or less. From the viewpoint of making the flexibility of the aluminum foil preferable, if there is an appropriate range for the liquid temperature, the upper limit is about 110 ° C. to 120 ° C. and a relatively small liquid under a sufficient liquid amount. If it is under the amount, it is considered to be about 100 to 110 ° C. From the same viewpoint, the lower limit value of the liquid temperature may be, for example, about 60 ° C. to 80 ° C. that can be plated, and is considered to vary depending on the type of the plating solution.

(1) Production of Aluminum Foil A plurality of aluminum foils (electrolytic aluminum foils) were produced by changing the plating solution and plating conditions as shown in Table 1 by electrolytic aluminum plating treatment using an electrolytic method. The plating solution is prepared using dimethylsulfone, which is a kind of dialkylsulfone, as a nonaqueous solvent, anhydrous aluminum chloride, which is a kind of aluminum halide, as a solute, and with or without the addition of a nitrogen-containing compound as an additive. did. Anhydrous aluminum chloride was prepared so that the blending amount with respect to 10 mol of dimethyl sulfone was about 3.8 mol. The nitrogen-containing compound was selected from trimethylamine hydrochloride (TMA-HCl), tetramethylammonium chloride (TMAC) and ammonium chloride (NH ₄ Cl), and was prepared by changing the blending amount with respect to 10 mol of dimethyl sulfone. As the plating conditions, the amount of the plating solution (liquid amount) and the temperature of the plating solution (liquid temperature) were listed, and these were variously changed to produce an aluminum foil. In addition, the current density was set so that the liquid temperature was maintained at a predetermined temperature during energization. The current density is obtained by dividing the current value applied between the electrodeposition region of the cathode drum 1c, which is the cathode, and the anode member 1d by the surface area of the portion immersed in the plating solution in the electrodeposition region. This is the value that can be obtained. In addition, the case where the produced aluminum foil was heat-treated was also examined.

Under plating conditions in which the amount of plating solution (amount of solution) is small, a plating solution having a volume of about 2 L was stored in a beaker serving as an electrolytic cell. A pure aluminum plate (Al plate) was used as the anode, and a flat plate surface (surface area of the electrodeposition region of about 12 cm ² ) of the pure titanium plate (Ti plate) was used as the cathode. Electric current was supplied between the anode and the cathode, and the current density was set so that the liquid temperature was maintained at a predetermined temperature. The Ti plate was taken out from the plating solution when Al deposited on the surface of the Ti plate grew to an aluminum film having a predetermined thickness. The aluminum film was peeled off from the surface of the Ti plate to obtain an aluminum foil. Subsequently, in order to remove the plating solution L adhering to the surface of the aluminum foil, it was washed with water and dried with warm air to produce a plurality of aluminum foils (electrolytic aluminum foils) having a thickness of 20 μm or less.

In plating conditions with a large amount of plating solution (liquid amount), an electrolytic aluminum foil manufacturing apparatus having the same configuration as the foil making apparatus 1 shown in FIG. 1 (for convenience, the foil making apparatus 1 shown in FIG. 1 is used). A plurality of aluminum foils (electrolytic aluminum foils) having a thickness of 20 μm or less were produced. About 500 L of the plating solution L was constructed, and the plating solution L was stored in the electrolytic bath 1 b so that the amount of the solution was about 200 L to about 250 L. The anode member 1d made of Al serving as the anode is immersed in the plating solution L, and the electrodeposition region of the cathode drum 1c serving as the cathode is partially immersed (approximately 800 cm ² ) in the plating solution L. did. Electric current was supplied between the anode and the cathode, and the current density was set so that the liquid temperature was maintained at a predetermined temperature. In synchronism with this, the cathode drum 1c was rotated at a predetermined speed so that Al deposited on the electrodeposition region of the cathode drum 1c grew out of the plating solution L when the aluminum film grew to a predetermined thickness. The aluminum coating from the plating solution L was peeled off from the electrodeposition region of the cathode drum 1c to obtain an aluminum foil F. Subsequently, in order to remove the plating solution L adhering to the surface of the aluminum foil F, it was washed with water and dried with warm air to produce a plurality of aluminum foils (electrolytic aluminum foils). Some aluminum foils after hot air drying were further heat-treated.

As described above, when all the aluminum foils were measured with a micrometer, the thicknesses of all the aluminum foils were 20 μm or less. Specifically, all the aluminum foils had a thickness in the range of 7 μm to 18 μm.
About all the produced aluminum foil, when Al content was measured for the surface (wetted surface) of the side which was in contact with the plating solution of aluminum foil by the fluorescent X ray analysis method mentioned above, Al content of all the aluminum foils was measured. Was 97% by mass or more. Specifically, all the aluminum foils had an Al content in the range of 99.00% by mass to 99.80% by mass.

(2) Effect of hydrogen amount of aluminum foil on flexibility Table 2 shows the H content contained in aluminum foils produced by various trial manufactures (Nos. 1 to 33 shown in Table 1) and the aluminum foils. The results of the flexibility test are shown. The H content of the aluminum foil is a numerical value (ppm) based on the quantitative value obtained by the TDS analysis described above. The flexibility test of the aluminum foil was performed by bending the aluminum foil at about 180 degrees so that the aluminum foil was folded in two. The case where the aluminum foil was cut at the bent portion was defined as “break”. The case where the aluminum foil was folded in two although a crack occurred in the bent portion was defined as “bendable (with crack)”. The case where the aluminum foil was folded in two without causing cracks in the bent portion was defined as “bendable (no crack)”. In the case of “bendable (with cracks)” and “bendable (without cracks)”, the aluminum foil can be wound in a coil shape, and a coiled aluminum foil can be produced. FIG. 2 is a graph created based on the numerical values shown in Table 2, and shows the relationship between the H content of the aluminum foil and the flexibility of the aluminum foil.

  From the results shown in Table 2 and FIG. It was found that when the H content of the aluminum foil exceeded 200 ppm by mass as shown in FIG. 8, the aluminum foil could not be flexible enough to be in the form of a double fold and ruptured at the bent portion. As a reference example, No. Even when the H content of the aluminum foil exceeds 200 ppm by mass as in 15, the aluminum foil can be flexible enough to be folded in two, and does not break at the bent portion (with cracks). I found out that there was a case. From this point of view, it has been found that as the H content of the aluminum foil is smaller, the tendency of the aluminum foil to become less brittle becomes stronger, and the aluminum foil has a preferable flexibility. It has been found that when the H content of the aluminum foil is 200 ppm or less by mass ratio, embrittlement of the aluminum foil is suppressed and the aluminum foil comes to have more preferable flexibility. Therefore, as aluminum foil, particularly as aluminum foil suitable for current collector applications, H detected from aluminum foil is 200 ppm or less, preferably 170 ppm or less, more preferably 160 ppm or less, and even more preferably 150 ppm or less. Conceivable.

(3) Variation in hydrogen content of aluminum foil Table 3 shows eight trials (Nos. 22, 25-27, 29-31 and No. 22 shown in Table 2) as prototypes made under the same plating conditions using the same plating solution. 33) is extracted and shown. In the plating solution, the additive (nitrogen-containing compound) is NH ₄ Cl, and the blending amount with respect to 10 mol of dimethylsulfone is about 0.20 mol. The plating conditions are a liquid volume of about 200 L to about 250 L, a liquid temperature of about 98 ° C., and a current density for maintaining the liquid temperature of about 80 mA / cm ² . No heat treatment was performed on the aluminum foil after washing and drying. From the results shown in Table 3, No. 1 with the smallest H content in the aluminum foil was obtained. No. 27 (118.11 ppm), the most common no. The difference of 25 (148.94 ppm) is 30.83 ppm, and the sample standard deviation of the eight data itself is about 11.72 ppm. When the unbiased variance square root is obtained from these eight data, it is estimated that the standard deviation of the H content of the aluminum foil produced under the same conditions using the same plating solution is about 12.53 ppm. Therefore, it is considered that the H content of the aluminum foil is preferably about 180 ppm in view of the fluctuation of about 20 ppm. Also from this viewpoint, it is considered that H detected from the aluminum foil is preferably 170 ppm or less, more preferably 160 ppm or less, and still more preferably 150 ppm or less.

(4) Effect of plating solution additive on flexibility of aluminum foil Table 4 shows four types of plating performed under substantially the same plating conditions by changing the amount of additive (additive content) added to the plating solution. The trials (Nos. 2 to 5) are extracted from Table 2 and added with the additive content. The additive (nitrogen-containing compound) is TMA-HCl. The additive content is changed as shown in Table 4 with respect to 10 mol of dimethyl sulfone. FIG. 3 is a graph created based on the numerical values shown in Table 4, and shows the relationship between the additive content and the H content of the aluminum foil. FIG. 4 is a graph created based on the numerical values shown in Table 4, and is a graph showing the relationship between the additive amount of the plating solution and the flexibility of the aluminum foil.

From the results shown in Table 4 and FIGS. 3 and 4, it was found that as the additive content increases, the H content of the aluminum foil is reduced, and the flexibility of the aluminum foil becomes favorable. From the viewpoint of the H content of the aluminum foil, as shown in FIG. 3, it can be seen that the H content tends to be about 200 ppm by mass with an additive content of about 0.05 mol exceeding 0.04 mol. It was. From the viewpoint of the flexibility of the aluminum foil, as shown in FIG. 4, an additive content of about 0.04 mol is not sufficient, and the additive content exceeds about 0.04 mol, and about 0.05 It has been found that increasing the mole, such as about 0.07 mole, about 0.10 mole, tends to make the aluminum foil flexible enough to be folded. When the relationship between the additive content (X) and the H content (Y) of the aluminum foil was examined, it was found that it well matched with the second order approximation formula: Y = 7520X ² −3160X + 350. According to the above quadratic approximation, when X is 0.05, Y is about 210, when X is 0.06, Y is about 185, when X is 0.07, Y is about 165, and X is 0.08. In this case, Y is about 145. Therefore, from the viewpoint of the H content of the aluminum foil, the content of the plating solution additive (for example, TMA-HCl) exceeds 0.05 mol (for example, 0.06 with respect to 10 mol of dialkyl sulfone (for example, dimethyl sulfone)). It has been found that it is preferably 0.07 mol or more, and more preferably 0.08 mol or more. From the viewpoint of improving the film formation rate of the aluminum coating, it has been confirmed that the additive content is preferably 2.0 mol or less, more preferably 1.5 mol or less. In addition, from the results shown in Tables 1 and 2, even if the additive (nitrogen-containing compound) is not TMA-HCl, if the H content of the aluminum foil is 200 ppm or less by mass ratio, the flexibility of the aluminum foil is It turns out that it becomes preferable.

(5) Effect of plating solution temperature on flexibility of aluminum foil Table 5 shows five types of trials (Nos. 13 to 15, 21, and 23) performed by changing the temperature (solution temperature) of the plating solution. These are extracted from Table 2 and added with liquid temperature, and are shown in ascending order of liquid temperature. The temperature (solution temperature) of the plating solution is changed as shown in Table 5. The current density was set so that the liquid temperature was maintained at a predetermined liquid temperature during energization. The additive (nitrogen-containing compound) is NH ₄ Cl. The additive content is about 0.20 mole per 10 moles of dimethylsulfone. The amount of plating solution (liquid amount) is No. 13 to 15 is about 2L, 21 and 23 are about 200L to about 250L. FIG. 5 is a graph created based on the numerical values shown in Table 5, and shows the relationship between the liquid temperature and the H content of the aluminum foil. FIG. 6 is a graph created based on the numerical values shown in Table 5, and is a graph showing the relationship between the liquid temperature and the flexibility of the aluminum foil.

From the results shown in Table 5 and FIGS. 5 and 6, it was found that when the temperature (solution temperature) of the plating solution is lowered, the H content of the aluminum foil is reduced and the flexibility of the aluminum foil is preferable. From the viewpoint of the H content of the aluminum foil, it was found that the H content tends to be about 200 ppm by mass at a liquid temperature of about 110 ° C. as shown in FIG. From the viewpoint of the flexibility of the aluminum foil, it was found that the flexibility of the aluminum foil tends to be foldable at a liquid temperature of less than 130 ° C. as shown in FIG. When the relationship between the liquid temperature (X) and the H content (Y) of the aluminum foil was examined, it was found that the second-order approximation formula: Y = 0.268X ² −46X + 2030 was well suited. According to the above quadratic approximation, when X is 110, Y is about 210, when X is 109, Y is about 200, when X is 105, Y is about 155, and when X is 100, Y is about 110. . Therefore, from the viewpoint of the H content of the aluminum foil, the liquid temperature is preferably less than 110 ° C, more preferably 105 ° C or less, and even more preferably 100 ° C or less. From the viewpoint of improving the deposition rate of the aluminum coating, it has been confirmed that the liquid temperature is preferably 120 ° C. or lower, more preferably 110 ° C. or lower, and even more preferably 100 ° C. or lower. In addition, from the result shown in Table 1 and Table 2, even if the liquid temperature is about 125 ° C. (No. 18) exceeding 110 ° C., when the H content of the aluminum foil is 200 ppm or less by mass ratio, It can be seen that flexibility is preferred.

(6) Effect of heat treatment on flexibility of aluminum foil No. 1 shown in Tables 1 and 2 18 and no. No. 19 differs only in the presence or absence of heat treatment (retention conditions at 460 ° C. for 180 minutes) on the aluminum foil after washing and drying. No heat-treated No. The H content of 18 aluminum foils is 173.13 ppm by mass. No. being heat-treated The H content of 18 aluminum foils is 52.65 ppm by mass. From this result, the H content of the aluminum foil was reduced by about 70% by applying heat treatment to the dried aluminum foil. In addition, No. The aluminum foil of 19 had a preferable flexibility so that it could be bent without cracking although fine voids were observed in the cross-sectional view. Therefore, it was found that it is effective to heat-treat the aluminum foil after washing and drying from the viewpoint of the flexibility of the aluminum foil.

  INDUSTRIAL APPLICABILITY The present invention is industrial in that an aluminum foil having a degree of flexibility (flexibility) that enables coiled winding of an aluminum foil and enables manufacture of the coiled aluminum foil can be provided. Has availability.

1. Electrolytic aluminum foil production equipment (foil making equipment)
1a. Lid 1b. Electrolytic cell 1c. Cathode drum 1d. Anode member 1e. Guide roll 1f. Foil drawer 1g. Gas supply port 1h. Heater power 1i. Heater 1j. Plating solution circulating device 1k. Ceiling 1m. Stir flow guide 1n. Stirring blade F. Aluminum foil G. Gas L. Plating solution

Claims (2)

  An aluminum foil having a thickness of 20 μm or less and 97 mass% or more composed of aluminum, wherein hydrogen detected from the aluminum foil has a mass ratio of 30 ppm to 200 ppm.   The aluminum foil of Claim 1 whose hydrogen detected from the said aluminum foil is 170 ppm or less by mass ratio.