Passivation solution, aluminum foil passivation treatment method, aluminum-plastic film and lithium battery

Abstract

The present invention discloses a passivation solution, an aluminum foil passivation treatment method, an aluminum-plastic film, and a lithium battery. The passivation solution comprises a trivalent chromium salt, a film-forming accelerator, a complexing agent, a thickener, nano-scale modified carbon black, a carbon black dispersant, and water. Treating aluminum foil with the passivation solution yields a passivation layer with excellent blackness, stable color, and high adhesion. The aluminum foil passivated with the passivation solution can be used to produce an aluminum-plastic film with excellent electrolyte resistance, good stability, and strong aging resistance. The aluminum-plastic film can meet the color requirements of mobile phone batteries. Furthermore, the passivation solution is cobalt-free and silver-free, low-toxic, low-cost, and environmentally friendly.

Description

Technical Field

[0001] The invention belongs to the technical field of aluminum foil surface treatment, and particularly relates to a passivation solution, an aluminum foil passivation treatment method, an aluminum-plastic film and a lithium battery. Background Art

[0002] Passivation solutions are chemical agents that, under certain conditions, form a dense oxide film (passivation film) on metal surfaces, enhancing the metal's corrosion resistance. Among metal passivation applications, aluminum foil surface passivation holds a special place due to its wide scope, high volume, and stringent requirements, and is gaining increasing attention within the industry and society at large. Currently, the composition and concentration of passivation agents, both domestically and internationally, are developing toward higher quality, higher stability, higher corrosion resistance, and lower toxicity.

[0003] There are common problems with the passivators currently used in the market. First, the passivators used for conventional aluminum foil are colorless after passivation and fail to impart color to the foil. Second, the currently available black passivation solution is reactive and requires a series of reactions with the zinc on the surface. It is only suitable for galvanized parts or zinc alloy surfaces, and there is a lack of black passivation solution suitable for aluminum foil passivation. Third, the passivation solution has poor corrosion resistance. Fourth, the traditional black passivation solution uses a large amount of hexavalent chromium, silver salts, and copper salts, which cause great damage and loss to the environment and resources, and will also lead to excessively high costs.

[0004] Therefore, the existing black passivation solution suitable for aluminum foil needs to be developed. Summary of the Invention

[0005] The present invention aims to solve, at least to a certain extent, one of the technical problems in the related art. To this end, one object of the present invention is to provide a passivation solution, an aluminum foil passivation treatment method, an aluminum-plastic film, and a lithium battery. The passivation solution, by introducing a nano-modified carbon black material, achieves a good coloring effect, and the black layer also has a good heat radiation reflection effect. At the same time, the introduction of the nano-material can also serve as a new sealing agent, improving the passivation effect and corrosion resistance of the passivation layer, and can also reduce the amount of trivalent chromium added to a certain extent. Treating aluminum foil with the passivation solution can produce a passivation layer with excellent blackness, stable color, and high adhesion. The aluminum foil passivated with the passivation solution can be prepared into an aluminum-plastic film with excellent electrolyte resistance, good stability, and strong aging resistance. The aluminum-plastic film can meet the color requirements of mobile phone batteries. At the same time, the passivation solution has the advantages of being cobalt-free and silver-free, low-toxic, low-cost, and environmentally friendly.

[0006] In one aspect, the present invention provides a passivation solution. According to an embodiment of the present invention, the passivation solution includes: a trivalent chromium salt, a film-forming accelerator, a complexing agent, a thickener, nano-scale modified carbon black, a carbon black dispersant, and water.

[0007] The passivation solution according to the above embodiment of the present invention includes a trivalent chromium salt, a film-forming accelerator, a complexing agent, a thickener, nano-scale modified carbon black, a carbon black dispersant and water. Among them, trivalent chromium salt is the main film-forming substance, film-forming promoter can promote film formation, and thickener helps film formation in the process of large-area coating, so as to obtain a film without streak defects, with better color and corrosion protection. Specifically, the passivation solution first performs acid etching on the surface of the aluminum foil, and then combines with the ligand with trivalent chromium as the center to form a metal complex, which is firmly bonded or adhered to the surface of the aluminum foil through the mutual bonding between the coordination bonds, thereby forming a layer of corrosion-resistant dense protective film on the surface of the aluminum foil; at the same time, the nano-scale modified carbon black has good spatial stability in water due to the advantages of surface hydrophilic groups and the small particle size of the nanomaterial itself, and exhibits good coloring uniformity. Moreover, under the action of the carbon black dispersant, the nano-scale modified carbon black is evenly and densely distributed in the passivation layer during the formation of the passivation layer, so that the passivation layer has uniform color, black and shiny, and has good blackness, which can meet the color requirements of mobile phone batteries and save the existing black ink coating process. Because the nano-scale modified carbon black is evenly dispersed in the passivation layer, the passivation layer further protects the stable and persistent color. Furthermore, the introduction of this modified nanomaterial acts as a novel passivation solution sealant, significantly improving the corrosion resistance of the passivation layer. Consequently, treating aluminum foil with this passivation solution yields a passivation layer with excellent blackness, stable color, and strong adhesion. This passivation solution can be used to produce aluminum-plastic films with excellent electrolyte resistance, good stability, and strong aging resistance. This aluminum-plastic film can meet the color requirements of mobile phone batteries. Furthermore, this passivation solution is cobalt-free and silver-free, low-toxic, low-cost, and environmentally friendly.

[0008] In addition, the passivation solution according to the above embodiment of the present invention may also have the following technical features:

[0009] In some embodiments of the present invention, based on 1 L of passivation solution, the amount of trivalent chromium salt added is 3g-30g, the amount of film-forming promoter added is 1g-10g, the amount of complexing agent added is 3g-30g, the amount of thickener added is 1g-4g, the amount of nano-modified carbon black added is 10g-50g, the amount of carbon black dispersant added is 10g-50g, and the balance is water. Thus, treating aluminum foil with this passivation solution can produce a passivation layer with excellent blackness, stable color, and high adhesion.

[0010] In some embodiments of the present invention, the pH of the passivation solution is 0.5 to 4.0. Thus, a passivation layer having excellent corrosion resistance can be obtained by treating aluminum foil with the passivation solution.

[0011] In some embodiments of the present invention, the particle size of the nano-scale modified carbon black is no greater than 100 nm, and the tinting strength is no less than 120%. Thus, by treating aluminum foil with the passivation solution, a passivation layer with excellent blackness and stable color can be obtained.

[0012] In some embodiments of the present invention, the nano-scale modified carbon black includes at least one of water-soluble carbon black powder, pigment carbon black and aqueous ink.

[0013] In some embodiments of the present invention, the modified group in the nano-scale modified carbon black includes at least one of a carboxyl group, an ester group, a hydroxyl group, and a carbonyl group.

[0014] In some embodiments of the present invention, the carbon black dispersant includes at least one of an anionic wetting and dispersing agent, a cationic wetting and dispersing agent, a controlled free radical hyperdispersant, a nonionic wetting and dispersing agent, and an amphoteric wetting and dispersing agent.

[0015] In some embodiments of the present invention, the anionic wetting and dispersing agent includes at least one of sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and sodium lauryl sulfate.

[0016] In some embodiments of the present invention, the trivalent chromium salt includes at least one of chromium nitrate, chromium sulfate, and chromium chloride.

[0017] In some embodiments of the present invention, the film-forming promoter includes at least one of potassium sulfate, sodium sulfate, potassium nitrate, phosphoric acid, sodium nitrate, fluorotitanic acid and polyacrylic acid.

[0018] In some embodiments of the present invention, the complexing agent includes at least one of a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid, and butanetetracarboxylic acid.

[0019] In some embodiments of the present invention, the monocarboxylic acid includes at least one of formic acid, acetic acid, propionic acid, amino acid, glycolic acid, acrylic acid and methacrylic acid.

[0020] In some embodiments of the present invention, the dicarboxylic acid includes at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, tartaric acid and malic acid.

[0021] In some embodiments of the present invention, the tribasic acid includes at least one of phosphoric acid and citric acid.

[0022] In some embodiments of the present invention, the thickener includes at least one of methyl cellulose and ethyl cellulose.

[0023] In its second aspect, the present invention provides a method for passivating aluminum foil. According to an embodiment of the present invention, the method comprises applying the aforementioned passivation solution to at least one side of the aluminum foil, followed by drying, to produce an aluminum foil having a black passivation layer. Thus, using this method to treat the aluminum foil, a passivation layer with excellent blackness, stable color, and high adhesion can be formed on the surface of the aluminum foil. The passivated aluminum foil can then be used to prepare a black aluminum-plastic film, resulting in a simple process and high production efficiency.

[0024] In addition, the aluminum foil passivation treatment method according to the above embodiment of the present invention may also have the following technical features:

[0025] In some embodiments of the present invention, the drying temperature is 120° C. to 240° C., and the drying time is 0.2 min to 3 min.

[0026] The third aspect of the present invention provides an aluminum-plastic film. According to an embodiment of the present invention, the aluminum-plastic film comprises, in order, a polyamide film layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer, and a polyolefin film layer; wherein the aluminum foil layer is prepared using the above-described method. As a result, the aluminum-plastic film exhibits excellent electrolyte resistance, good stability, and strong aging resistance.

[0027] In addition, the aluminum-plastic film according to the above embodiment of the present invention may also have the following technical features:

[0028] In some embodiments of the present invention, the thickness of the polyamide film layer is 5 μm to 25 μm.

[0029] In some embodiments of the present invention, the thickness of the first adhesive layer is 3 μm to 5 μm.

[0030] In some embodiments of the present invention, the passivation liquid is applied to the side of the aluminum foil layer away from the second adhesive layer, and the thickness of the obtained passivation layer is 0.03 μm to 1 μm.

[0031] In some embodiments of the present invention, the passivation liquid is applied to the side of the aluminum foil layer away from the first adhesive layer, and the thickness of the obtained passivation layer is 0.03 μm to 1 μm.

[0032] In some embodiments of the present invention, the dry film weight of the passivation layer is 0.01 g / m 2 ~0.3g / m 2 In this way, a passivation layer with bright black color and good anti-corrosion effect can be obtained.

[0033] In some embodiments of the present invention, the thickness of the aluminum foil layer is 20 μm to 50 μm.

[0034] In some embodiments of the present invention, the thickness of the second adhesive layer is 2 μm to 10 μm.

[0035] In some embodiments of the present invention, the thickness of the polyolefin film layer is 20 μm to 40 μm.

[0036] In a fourth aspect, the present invention provides a lithium battery. According to an embodiment of the present invention, the lithium battery utilizes the aforementioned aluminum-plastic film. As a result, the lithium battery has excellent electrical performance and low production cost.

[0037] Additional aspects and advantages of the present invention will be set forth in part in the description which follows and, in part, will be obvious from the description which follows, or may be learned by practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] The above and / or additional aspects and advantages of the present invention will become apparent and readily understood from the following description of the embodiments with reference to the accompanying drawings, in which:

[0039] Figure 1 Schematic diagram of the structure of the aluminum-plastic film according to an embodiment of the present invention. DETAILED DESCRIPTION

[0040] The embodiments of the present invention are described in detail below, which are intended to explain the present invention but are not to be construed as limiting the present invention.

[0041] In one aspect, the present invention provides a passivation solution. According to an embodiment of the present invention, the passivation solution includes: a trivalent chromium salt, a film-forming accelerator, a complexing agent, a thickener, nano-scale modified carbon black, a carbon black dispersant, and water.

[0042] The passivation solution according to the above embodiment of the present invention includes a trivalent chromium salt, a film-forming accelerator, a complexing agent, a thickener, nano-scale modified carbon black, a carbon black dispersant and water. Among them, trivalent chromium salt is the main film-forming substance, film-forming promoter can promote film formation, and thickener helps film formation in the process of large-area coating, so as to obtain a film without streak defects, with better color and corrosion protection. Specifically, the passivation solution first performs acid etching on the surface of the aluminum foil, and then combines with the ligand with trivalent chromium as the center to form a metal complex, which is firmly bonded or adhered to the surface of the aluminum foil through the mutual bonding between the coordination bonds, thereby forming a layer of corrosion-resistant dense protective film on the surface of the aluminum foil; at the same time, the nano-scale modified carbon black has good spatial stability in water due to the advantages of surface hydrophilic groups and the small particle size of the nanomaterial itself, and exhibits good coloring uniformity. Moreover, under the action of the carbon black dispersant, the nano-scale modified carbon black is evenly and densely distributed in the passivation layer during the formation of the passivation layer, so that the passivation layer has uniform color, black and shiny, and has good blackness, which can meet the color requirements of mobile phone batteries and save the existing black ink coating process. Because the nano-scale modified carbon black is evenly dispersed in the passivation layer, the passivation layer further protects the stable and persistent color. Furthermore, the introduction of this modified nanomaterial acts as a novel passivation solution sealant, significantly improving the corrosion resistance of the passivation layer. Consequently, treating aluminum foil with this passivation solution yields a passivation layer with excellent blackness, stable color, and strong adhesion. This passivation solution can be used to produce aluminum-plastic films with excellent electrolyte resistance, good stability, and strong aging resistance. This aluminum-plastic film can meet the color requirements of mobile phone batteries. Furthermore, this passivation solution is cobalt-free and silver-free, low-toxic, low-cost, and environmentally friendly.

[0043] It should be noted that the trivalent chromium salt, film-forming promoter, complexing agent, thickener, nano-scale modified carbon black and carbon black dispersant are conventional materials in the field, and those skilled in the art can select them according to actual conditions. For example, the trivalent chromium salt includes at least one of chromium nitrate, chromium sulfate and chromium chloride; the film-forming promoter includes at least one of potassium sulfate, sodium sulfate, potassium nitrate, phosphoric acid, sodium nitrate, fluorotitanic acid and polyacrylic acid; the complexing agent includes at least one of monocarboxylic acid, dicarboxylic acid, tricarboxylic acid and butanetetracarboxylic acid, and the monocarboxylic acid includes formic acid, acetic acid, propionic acid , amino acids, glycolic acid, acrylic acid and methacrylic acid; dicarboxylic acids include at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, tartaric acid and malic acid; tribasic acids include at least one of phosphoric acid and citric acid; thickeners include at least one of methyl cellulose and ethyl cellulose; nano-scale modified carbon black includes at least one of water-soluble carbon black powder, pigment carbon black and water-based ink; further, the modified groups in the nano-scale modified carbon black include at least one of carboxyl, ester, hydroxyl and carbonyl groups. Carbon black dispersants need to have good compatibility with aqueous base materials to prevent floating color and stabilize various pigments (carbon black). Therefore, carbon black dispersants include at least one of anionic wetting dispersants, cationic wetting dispersants, controlled free radical hyperdispersants, nonionic wetting dispersants and amphoteric wetting dispersants. Anionic wetting dispersants include at least one of sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and sodium dodecylsulfonate.

[0044] According to an embodiment of the present invention, the pH of the passivation solution is 0.5 to 4.0. The inventors have found that when the pH of the passivation solution is lower than 0.5, the passivation solution is too acidic, the reaction rate is too fast, and the passivation layer has poor density and corrosion resistance. When the pH of the passivation solution is higher than 4.0, the passivation solution is less acidic, the reaction rate is too low, and the passivation effect is weakened. Therefore, the present application uses a passivation solution with a pH of 0.5-4.0 to treat aluminum foil to obtain a passivation layer with excellent corrosion resistance.

[0045] According to an embodiment of the present invention, based on 1L of passivation solution, the amount of trivalent chromium salt added is 3g~30g, the amount of film-forming promoter added is 1g~10g, the amount of complexing agent added is 3g~30g, the amount of thickener added is 1g~4g, the amount of nano-scale modified carbon black added is 10g~50g, the amount of carbon black dispersant added is 10g~50g, and the balance is water. The inventors found that if the amount of trivalent chromium salt added is too much, the passivation layer contains excessive trivalent chromium, the appearance of the passivation layer deteriorates, and the surface of the passivation layer becomes rough. If the amount of trivalent chromium salt added is too little, the adhesion between the passivation layer and the aluminum foil is low, and the density and corrosion resistance of the passivation layer are poor. If the amount of film-forming promoter added is too much, the film structure is not loose, and if the amount of film-forming promoter added is too little, the film-forming speed is too slow, and the film is too thin. If the amount of complexing agent added is too much, the reaction rate is too fast, and the corrosion resistance of the passivation layer is poor. If the amount of complexing agent added is too little, the reaction speed is too slow, and the density of the passivation layer is poor. If the amount of nano-modified carbon black added is too much, the adhesion of the passivation layer deteriorates. If the amount of nano-modified carbon black added is too little, the coloring effect is poor, the blackness of the passivation layer is insufficient, and the passivation layer becomes gray. If the amount of carbon black dispersant added is too much, agglomeration problems are likely to occur. If the amount of carbon black dispersant added is too little, the carbon black dispersion effect is affected, the system is unstable, and sedimentation and floating color are prone to occur. Therefore, the present application uses the passivation solution obtained by the above-mentioned formula of the addition amounts of each component to treat the aluminum foil, and can obtain a passivation layer with excellent blackness, stable color, high adhesion and corrosion resistance.

[0046] According to an embodiment of the present invention, the particle size of the nano-modified carbon black is no greater than 100nm, and the tinting strength is no less than 120%. The inventors have found that if the particle size of the nano-modified carbon black is too large, it will be poorly dispersed and easily sedimented; if the tinting strength is too low, the coloring effect is poor and the passivation layer is not black enough. Therefore, the present application uses a passivation solution prepared with nano-modified carbon black with a particle size no greater than 100nm and a tinting strength no less than 120% to treat aluminum foil, which can produce a passivation layer with excellent blackness and stable color.

[0047] In its second aspect, the present invention provides a method for passivating aluminum foil. According to an embodiment of the present invention, the method comprises applying the aforementioned passivation solution to at least one side of the aluminum foil, followed by drying, to produce an aluminum foil having a black passivation layer. Thus, using this method to treat the aluminum foil, a passivation layer with excellent blackness, stable color, and high adhesion can be formed on the surface of the aluminum foil. The passivated aluminum foil can then be used to prepare a black aluminum-plastic film, resulting in a simple process and high production efficiency.

[0048] Furthermore, the drying temperature is 120-250°C, and the drying time is 0.2-3 minutes. The inventors have also discovered that after aging the prepared passivation solution for 3-10 days, a coordination reaction occurs in the passivation solution, increasing the number of free hydrogen ions. This significantly promotes the passivation solution's etching of the aluminum foil surface, enhancing the anti-corrosion effect of the passivation layer. It should be noted that the characteristics and advantages described above for the passivation solution also apply to this aluminum foil passivation treatment method and will not be further elaborated here.

[0049] The third aspect of the present invention provides an aluminum-plastic film. Figure 1 The aluminum-plastic film comprises, in order, a polyamide film layer 10, a first adhesive layer 20, an aluminum foil layer 30, a second adhesive layer 40, and a polyolefin film layer 50; the aluminum foil layer 30 is prepared using the above-described method. As a result, the aluminum-plastic film exhibits excellent electrolyte resistance, good stability, and strong aging resistance, and can meet color requirements for mobile phone batteries.

[0050] Those skilled in the art will appreciate that the matte surface of the aluminum foil can be treated with the passivation solution described in this application to produce a black passivation layer, thereby imparting a black color to the aluminum-plastic film. Alternatively, the non-matte surface of the aluminum foil can be treated with the passivation solution described in this application to produce a black passivation layer, and the non-matte surface of the aluminum foil can also be treated with a passivation solution other than that described in this application to form a passivation layer. It should be noted that the features and advantages described above for the passivation solution and aluminum foil passivation treatment method also apply to the aluminum-plastic film and will not be further elaborated here.

[0051] According to an embodiment of the present invention, referring to Figure 1 The thickness of the polyamide film layer 10 is 5 to 25 μm; the thickness of the first adhesive layer 20 is 3 to 5 μm; a passivation solution is applied to the side of the aluminum foil layer 30 away from the second adhesive layer 40, and the resulting passivation layer 31 has a thickness of 0.03 to 1 μm; a passivation solution is applied to the side of the aluminum foil layer 30 away from the first adhesive layer 20, and the resulting passivation layer 32 has a thickness of 0.03 to 1 μm; the thickness of the aluminum foil layer 30 is 20 to 50 μm; the thickness of the second adhesive layer 40 is 2 to 10 μm; and the thickness of the polyolefin film layer 50 is 20 to 40 μm. As a result, the aluminum-plastic film has an excellent black color effect and is resistant to electrolytes.

[0052] According to an embodiment of the present invention, the dry film weight of the passivation layer is 0.01 g / m 2 ~0.3g / m 2 The inventors found that if the thickness of the passivation layer on one side of the aluminum foil is too thick, the passivation layer structure is loose and cannot achieve a good passivation effect; if the thickness is too thin, the passivation layer is not dense enough, the corrosion resistance is poor, and the blackness is low. Therefore, this application adopts a dry film weight of 0.01g / m 2 ~0.3g / m2 The passivation layer can obtain a black, bright aluminum-plastic film with good anti-corrosion effect.

[0053] In a fourth aspect, the present invention provides a lithium battery. According to an embodiment of the present invention, the lithium battery utilizes the aforementioned aluminum-plastic film. As a result, the lithium battery exhibits excellent electrical performance and low production costs. It should be noted that the features and advantages described above for the aluminum-plastic film also apply to this lithium battery and will not be further elaborated here.

[0054] The present invention is described below with reference to specific examples. It should be noted that these examples are merely illustrative and do not limit the present invention in any way.

[0055] Example 1

[0056] Use 40μm aluminum foil, and degrease and activate its surface. Refer to the cleaning method of Chinese patent CN100545308. The specific ratio of the passivation solution is as follows: based on 1L of passivation solution, 20g of chromium nitrate, 6g of polyacrylic acid, 20g of tartaric acid, 50g of pigment carbon black, 40g of sodium hexametaphosphate, 4g of methyl cellulose, and the rest is pure water. Among them, the particle size of the nano-modified carbon black is 60nm, the tinting strength is 136%, and the pH of the passivation solution is 1.5.

[0057] The above passivation solution was applied on both sides of the cleaned aluminum foil and dried at 200°C for 0.5 min. The passivation layer obtained was black and shiny. The dry film weight of the passivation layer on one side was 0.2 g / m 2 , and a 3μm outer layer of glue is coated on the matte surface of the passivated aluminum foil and then composited with a 25μm polyamide film, and a 3μm inner layer of glue is coated on the glossy surface of the aluminum foil and then composited with a 40μm polypropylene film to obtain a black aluminum-plastic film.

[0058] Example 2

[0059] Use 35μm aluminum foil, and degrease and activate its surface. Refer to the cleaning method of Chinese patent CN100545308. The specific ratio of the passivation solution is as follows: based on 1L of passivation solution, 30g of chromium sulfate, 10g of sodium sulfate, 10g of citric acid, 20g of water-soluble carbon black powder, 50g of sodium pyrophosphate, 1g of ethyl cellulose, and the rest is pure water. Among them, the particle size of the nano-modified carbon black is 40nm, the tinting strength is 140%, and the pH of the passivation solution is 2.8.

[0060] The above passivation solution was applied on both sides of the cleaned aluminum foil and dried at 120°C for 3 minutes. The passivation layer obtained was black and shiny. The dry film weight of the passivation layer on one side was 0.08g / m 2, and a 3μm outer layer of glue is coated on the matte surface of the passivated aluminum foil and then composited with a 15μm polyamide film, and a 3μm inner layer of glue is coated on the glossy surface of the aluminum foil and then composited with a 30μm polypropylene film to obtain a black aluminum-plastic film.

[0061] Example 3

[0062] Use 35μm aluminum foil, and degrease and activate its surface. Refer to the cleaning method of Chinese patent CN100545308. The specific ratio of the passivation solution is as follows: based on 1L of passivation solution, 20g of chromium nitrate, 6g of polyacrylic acid, 20g of butanetetracarboxylic acid, 50g of pigment carbon black, 40g of sodium hexametaphosphate, 4g of methyl cellulose, and the rest is pure water. Among them, the particle size of the nano-modified carbon black is 80nm, the tinting strength is 126%, and the pH of the passivation solution is 2.0.

[0063] The above passivation solution was applied on both sides of the cleaned aluminum foil and dried at 160°C for 2 minutes. The passivation layer obtained was black and shiny. The dry film weight of the passivation layer on one side was 0.15g / m 2 , and a 3μm outer layer of glue is coated on the matte surface of the passivated aluminum foil and then composited with a 15μm polyamide film, and a 3μm inner layer of glue is coated on the glossy surface of the aluminum foil and then composited with a 40μm polypropylene film to obtain a black aluminum-plastic film.

[0064] Comparative Example 1

[0065] Use 40μm aluminum foil, and degrease and activate its surface. Refer to the cleaning method of Chinese patent CN100545308. The specific ratio of the passivation solution is as follows: based on 1L of passivation solution, 20g of chromium sulfate, 6g of polyacrylic acid, 30g of maleic acid, 5g of water-soluble carbon black powder, 40g of sodium hexametaphosphate, 4g of ethyl cellulose, and the rest is pure water. Among them, the particle size of the nano-modified carbon black is 80nm, the tinting strength is 130%, and the pH of the passivation solution is 2.4.

[0066] The passivation liquid was applied on both sides of the cleaned aluminum foil and dried at 180°C for 1 minute. The passivation layer obtained was black in appearance, and the dry film weight of the passivation layer on one side was 0.15g / m 2 , and a 3μm outer layer of glue is coated on the matte surface of the passivated aluminum foil and then composited with a 25μm polyamide film, and a 3μm inner layer of glue is coated on the glossy surface of the aluminum foil and then composited with a 40μm polypropylene film to obtain a black aluminum-plastic film.

[0067] Comparative Example 2

[0068] Use 40μm aluminum foil, and degrease and activate its surface. Refer to the cleaning method of Chinese patent CN100545308. The specific ratio of the passivation solution is as follows: based on 1L of passivation solution, 5g of chromium nitrate, 6g of sodium nitrate, 3g of phosphoric acid, 80g of pigment carbon black, 40g of sodium pyrophosphate, 4g of ethyl cellulose, and the rest is pure water. Among them, the particle size of the nano-modified carbon black is 60nm, the tinting strength is 132%, and the pH of the passivation solution is 3.0.

[0069] The passivation liquid was applied on both sides of the cleaned aluminum foil and dried at 180°C for 0.5 min. The passivation layer was black and the dry film weight of the passivation layer on one side was 0.06 g / m 2 , and a 3μm outer layer of glue is coated on the matte surface of the passivated aluminum foil and then composited with a 25μm polyamide film, and a 3μm inner layer of glue is coated on the glossy surface of the aluminum foil and then composited with a 40μm polypropylene film to obtain a black aluminum-plastic film.

[0070] Comparative Example 3

[0071] Use 40μm aluminum foil and degrease and activate its surface. Refer to the cleaning method of Chinese patent CN100545308 and purchase commercial passivation liquid. Apply the commercial passivation liquid on both sides of the cleaned aluminum foil and dry it at 180℃ for 1min. The passivation layer obtained has a dry film weight of 0.1g / m2 on one side. 2 , and a 3μm outer layer of glue is coated on the matte surface of the passivated aluminum foil and then composited with a 25μm polyamide film, and a 3μm inner layer of glue is coated on the glossy surface of the aluminum foil and then composited with a 40μm polypropylene film to obtain an aluminum-plastic film.

[0072] The properties of the passivation layers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 were measured, and the specific method is as follows:

[0073] (1) The apparent color of the aluminum foil passivation layer.

[0074] (2) Copper Sulfate Drop Test: The copper sulfate solution is prepared as follows: 40 g / L CuSO4·5H2O, 30 g / L NaCl, and 18 ml / L 30% HCl. At room temperature, a syringe is used to drop the copper sulfate solution onto the surface of the passivation layer. The color change of the copper sulfate is observed, and the time it takes for the color to change from blue to black is recorded with a stopwatch. Three points are tested on each sample and the average value is calculated.

[0075] (3) Adhesion test: Use a grid knife to draw grids on the surface, and use 3M tape to stick to the grid positions. Press the tape tightly to squeeze out the bubbles in the middle of the tape, keep it for 1 minute, and then quickly tear off the tape to observe whether the passivation layer falls off.

[0076] The apparent colors of the passivation layers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 1.

[0077] Table 1

[0078] Apparent color Unpassivated aluminum foil silver Example 1 black Example 2 black Example 3 black Comparative Example 1 light gray Comparative Example 2 black Comparative Example 3 silver

[0079] As can be seen from Table 1, the passivation layers prepared using Examples 1 to 3 are all black, and Comparative Example 1 uses less carbon black, so the color of the passivation layer is light gray.

[0080] The adhesion and corrosion resistance test results of the passivation layers prepared in Examples 1 to 3 and Comparative Examples 1 to 3 are shown in Table 2.

[0081] Table 2

[0082] Adhesion test Copper sulfate drop test(s) Example 1 No shedding 50 Example 2 No shedding 66 Example 3 No shedding 58 Comparative Example 1 No shedding 63 Comparative Example 2 Falling off / Comparative Example 3 No shedding 45 Unpassivated aluminum foil / 2

[0083] As can be seen from the data of the copper sulfate drop test in Table 2, the color of the copper sulfate solution changes after 2 seconds of adding copper sulfate to the unpassivated aluminum foil. However, after adding copper sulfate, the color of the aluminum foil passivated by the passivation solution of the present application does not change until more than 50 seconds have passed. Although the color change of copper sulfate does not occur until 63 seconds in Comparative Example 1, the passivation layer prepared in Comparative Example 1 is light gray. Due to the excessive addition of carbon black in Comparative Example 2, the adhesion of the passivation layer is poor. This shows that the aluminum foil treated with the passivation solution of the present application forms a black passivation layer on the aluminum foil, which can protect the aluminum foil and make the aluminum foil have excellent corrosion resistance. As can be seen from the adhesion test results in Table 2, the passivation layer of the aluminum foil of the present application has good adhesion and does not fall off.

[0084] The properties of the aluminum-plastic films prepared in Examples 1 to 3 and Comparative Example 3 were measured, and the specific method is as follows:

[0085] (1) Electrolyte resistance test: The prepared aluminum-plastic film was cut into strips with a width of 15 mm. The strips were subjected to a mechanical property test to obtain the initial tensile strength of the aluminum foil CPP film. The obtained aluminum-plastic film strips were placed in an electrolyte (containing 1000 ppm water) at 85°C and the peel strength test was performed every other day.

[0086] (2) Water boiling resistance test: After punching the aluminum-plastic film sample, put it into 70℃ water and boil it for 1 day. Observe the surface changes of the sample before and after boiling to confirm whether there are defects such as delamination, white lines, discoloration, etc. For each sample test, place three parallel samples for comparison.

[0087] (3) Heat resistance test: After punching the aluminum-plastic film sample, place it under high temperature conditions of 85℃ for 1 day and then take it out. Observe the changes in the appearance of the sample before and after to confirm whether there are defects such as delamination, white lines, discoloration, etc. For each sample test, place three parallel samples for comparison.

[0088] (4) Moisture and heat resistance test: After punching the aluminum-plastic film sample, place it at 60℃ / 90%RH for 3 days. Observe the surface changes of the sample before and after moisture and heat resistance to confirm whether there are defects such as delamination, white lines, discoloration, etc. For each sample test, place three parallel samples for comparison.

[0089] The electrolyte resistance test results of the aluminum-plastic films prepared in Examples 1 to 3 and Comparative Example 3 are shown in Table 3.

[0090] Table 3

[0091]

[0092]

[0093] From the results in Table 3, it can be seen that the initial peel force of the aluminum-plastic films prepared in Examples 1 to 3 of the present application is relatively high, and the peel force does not change much after soaking in electrolyte, while the initial peel force of the commercially available aluminum-plastic film of Comparative Example 3 is relatively small, and the peel force changes significantly after soaking in electrolyte, especially, indicating that the aluminum-plastic film of the present application has excellent electrolyte resistance.

[0094] The aging resistance test results of Examples 1 to 3 are shown in Table 4.

[0095] Table 4

[0096] Boiling water resistance Heat resistance Moisture and heat resistance Example 1 No change No change No change Example 2 No change No change No change Example 3 No change No change No change

[0097] From the results in Table 4, it can be seen that the aluminum-plastic films of the present application are all resistant to boiling water, indicating that the aluminum-plastic films have good stability; the aluminum-plastic films of the present application are all resistant to heat and humidity, indicating that the aluminum-plastic films have good aging resistance.

[0098] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0099] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A passivation solution, characterized in that: include: Trivalent chromium salt, film-forming accelerator, complexing agent, thickener, nano-scale modified carbon black, carbon black dispersant and water, Based on 1L of passivation solution, the amount of trivalent chromium salt added is 3g-30g, the amount of film-forming accelerator added is 1g-10g, the amount of complexing agent added is 3g-30g, the amount of thickener added is 1g-4g, the amount of nano-scale modified carbon black added is 10g-50g, the amount of carbon black dispersant added is 10g-50g, and the balance is water. The nano-scale modified carbon black includes at least one of water-soluble carbon black powder, pigment carbon black and water-based ink; The modified groups in the nano-scale modified carbon black include at least one of a carboxyl group, an ester group, a hydroxyl group and a carbonyl group.

2. The passivation solution according to claim 1, characterized in that The pH of the passivation solution is 0.5-4.

0.

3. The passivation solution according to claim 1 or 2, wherein The particle size of the nano-scale modified carbon black is not greater than 100 nm, and the tinting strength is not less than 120%.

4. The passivation solution according to claim 1 or 2, wherein The carbon black dispersant includes at least one of anionic wetting dispersants, cationic wetting dispersants, controlled free radical hyperdispersants, nonionic wetting dispersants and amphoteric wetting dispersants; Optionally, the anionic wetting and dispersing agent includes at least one of sodium hexametaphosphate, sodium pyrophosphate, sodium tripolyphosphate and sodium lauryl sulfate.

5. The passivation solution according to claim 1 or 2, characterized in that: The trivalent chromium salt includes at least one of chromium nitrate, chromium sulfate and chromium chloride; Optionally, the film-forming promoter includes at least one of potassium sulfate, sodium sulfate, potassium nitrate, phosphoric acid, sodium nitrate, fluorotitanic acid and polyacrylic acid; Optionally, the complexing agent includes at least one of a monocarboxylic acid, a dicarboxylic acid, a tricarboxylic acid, and butanetetracarboxylic acid; Optionally, the monocarboxylic acid comprises at least one of formic acid, acetic acid, propionic acid, amino acid, glycolic acid, acrylic acid and methacrylic acid; Optionally, the dicarboxylic acid comprises at least one of oxalic acid, malonic acid, succinic acid, glutaric acid, maleic acid, tartaric acid and malic acid; Optionally, the triprotic acid includes at least one of phosphoric acid and citric acid; Optionally, the thickener includes at least one of methyl cellulose and ethyl cellulose.

6. A passivation treatment method for aluminum foil, characterized in that: include: The passivation solution according to any one of claims 1 to 5 is applied to at least one side of the aluminum foil, and then dried to obtain the aluminum foil having a black passivation layer.

7. The method according to claim 6, characterized in that The drying temperature is 120° C. to 250° C., and the drying time is 0.2 min to 3 min.

8. An aluminum-plastic film, characterized in that: The method comprises, in sequence, a polyamide film layer, a first adhesive layer, an aluminum foil layer, a second adhesive layer and a polyolefin film layer; Wherein, the aluminum foil layer is prepared by the method according to claim 6 or 7.

9. The aluminum-plastic film according to claim 8, characterized in that: The thickness of the polyamide film layer is 5 μm to 25 μm; Optionally, the thickness of the first adhesive layer is 3 μm to 5 μm; Optionally, the passivation solution is applied to the side of the aluminum foil layer away from the second adhesive layer, and the thickness of the obtained passivation layer is 0.03 μm to 1 μm; Optionally, the passivation solution is applied to the side of the aluminum foil layer away from the first adhesive layer, and the thickness of the obtained passivation layer is 0.03 μm to 1 μm; Optionally, the dry film weight of the passivation layer is 0.01 g / m 2 ~0.3g / m 2 ; Optionally, the thickness of the aluminum foil layer is 20 μm to 50 μm; Optionally, the thickness of the second adhesive layer is 2 μm to 10 μm; Optionally, the polyolefin film layer has a thickness of 20 μm to 40 μm.

10. A lithium battery, characterized in that: The aluminum-plastic film according to claim 8 or 9 is used.

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