Composite aluminum foil, method for preparing composite aluminum foil and electroplating solution

Abstract

The invention relates to a composite aluminum foil, a method for preparing the composite aluminum foil and electroplating liquid. The electroplating liquid for preparing the composite aluminum foil comprises ionic liquid and an additive, wherein the additive is selected from one or more of nicotinic acid, methyl nicotinate, 3-methylpyridine, benzoic acid and ethylene glycol. The method for preparing the composite aluminum foil comprises the step of preparing the composite aluminum foil by adopting the electroplating liquid. By means of the electroplating liquid and the method, the composite aluminum foil with the improved electroplating uniformity can be prepared.

Description

Technical Field

[0001] The present invention relates to the technical field of composite current collector production, and specifically to a composite aluminum foil, a method for preparing the same and an electroplating solution, and more specifically to an electroplating solution for preparing the composite aluminum foil based on molten salt aluminum electroplating technology, a method for preparing the composite aluminum foil using the electroplating solution, and the composite aluminum foil prepared by the method. Background Art

[0002] In recent years, composite current collectors, as the new type of current collector material with the greatest potential for replacement, can effectively improve the safety of lithium batteries, reduce material costs, and increase energy density. In addition to the commonly used preparation process based on physical vapor deposition technology, the composite aluminum foil preparation technology based on molten salt electroplating technology has obvious advantages in improving production efficiency, reducing equipment costs, and reducing polymer substrate damage.

[0003] However, on the one hand, the aluminum coating is prone to produce dendrites during the growth process, which seriously affects the flatness and conductivity uniformity of the composite aluminum foil surface; on the other hand, due to the high viscosity of ionic liquids, the problem of low ion migration rate is prone to occur during the electroplating process, which in turn produces concentration polarization, affecting the growth uniformity and deposition quality of the deposited aluminum layer.

[0004] Therefore, the existing technology has the problem of low electroplating uniformity of composite aluminum foil. Regarding the composite aluminum foil preparation technology based on molten salt electroplating, it is urgent to develop a plating solution and an electroplating method to improve the electroplating uniformity of the composite aluminum foil. Summary of the invention

[0005] The main purpose of the present invention is to provide an electroplating solution for preparing a composite aluminum foil, a method for preparing a composite aluminum foil, and a composite aluminum foil prepared by the method, so as to solve the problem of low electroplating uniformity of the composite aluminum foil in the prior art.

[0006] In order to achieve the above-mentioned purpose, according to the first aspect of the present disclosure, a plating solution for preparing a composite aluminum foil is provided, the plating solution comprising an ionic liquid and an additive, the additive being one or more selected from nicotinic acid, methyl nicotinate, 3-methylpyridine, benzoic acid, and ethylene glycol.

[0007] Furthermore, the concentration of the above additive in the electroplating solution is 1-20 mmol / L.

[0008] Furthermore, the ionic liquid comprises anhydrous aluminum chloride and an organic salt, and the molar ratio of anhydrous aluminum chloride to the organic salt is 1 to 3:1, wherein the organic salt is one or more selected from bromoethylpyridine, n-butylpyridinium chloride, 1-ethyl-3-methylimidazole chloride, urea and acetamide.

[0009] According to a second aspect of the present disclosure, a method for preparing a composite aluminum foil is provided. The method adopts the electroplating solution described in the first aspect of the present invention to prepare the composite aluminum foil.

[0010] Furthermore, the method comprises the following steps: step S1: pretreatment of polymer substrate: providing a polymer substrate, and performing surface modification on at least one surface of the polymer substrate by corona treatment or chemical etching solution to obtain a surface-modified polymer substrate; step S2: preparation of conductive layer: covering the above-mentioned at least one surface of the surface-modified polymer substrate with a conductive material by chemical plating or coating or vapor deposition to obtain a polymer substrate covered with a conductive layer; step S3: aluminum layer plating: placing the polymer substrate covered with a conductive layer in the electroplating solution of the present invention, depositing an aluminum layer on the surface of the conductive layer away from the polymer substrate by electroplating, and performing heating and pressurization treatment to obtain a composite aluminum foil, wherein the heating range of the heating and pressurization treatment is 30 to 65°C, the pressurization range is 0.2 to 20 MPa, and the treatment time is 0.5 to 60 min.

[0011] Furthermore, in step S3, the temperature of the electroplating solution is controlled to be in the range of 15 to 55°C.

[0012] Furthermore, in step S2, after covering the conductive material, heating and pressurizing treatment is performed to obtain a polymer substrate covered with a conductive layer. The heating range of the heating and pressurizing treatment in step S2 is 30 to 65°C, the pressurizing range is 0.2 to 20 MPa, and the treatment time is 0.5 to 60 min.

[0013] Furthermore, the method of the present invention further comprises, after step S3: step S4: post-plating cleaning: placing the composite aluminum foil in an organic cleaning solution for cleaning, wherein the organic cleaning solution comprises one or more selected from ethyl acetate, acetonitrile, ethanol and ethylene glycol.

[0014] Further, in step S3, electroplating is performed under a gradually increasing voltage, wherein the voltage is controlled to increase from an initial value in the range of 0 to 10 V to 5 to 35 V at a rate of 0.5 to 25 V / min.

[0015] Further, in step S1, the polymer substrate is one selected from polyethylene terephthalate, polypropylene, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyamide, polyimide, polyoxymethylene, poly(p-phenylene sulfide), poly(p-phenylene ether) and polyethylene glycol.

[0016] Further, in step S1, the chemical etching solution is an aqueous solution containing one or more of sulfuric acid, potassium permanganate, potassium dichromate, chloric acid, sodium hydroxide, nitric acid and hydrogen peroxide.

[0017] Further, in step S2, the conductive material is one or more selected from carbon, copper, aluminum, nickel, silver, gold and graphene.

[0018] Furthermore, the method is carried out continuously or discontinuously.

[0019] According to a third aspect of the present disclosure, a composite aluminum foil is provided. The composite aluminum foil is prepared by the method described in the second aspect of the present invention.

[0020] As mentioned above, dendrite formation and low local deposition rate due to concentration polarization are prone to occur during the implementation of aluminum electroplating, which in turn leads to low electroplating uniformity of composite aluminum foil. According to the technical solution disclosed in the present invention, a plating solution and an electroplating method that can be used to improve the electroplating uniformity of composite aluminum foil are provided. By introducing specific additives into the ionic liquid electrodeposition system, the electrochemical reduction potential of the active species can be changed, thereby affecting the electrochemical crystallization process of the grains, significantly improving the microstructure and performance of the deposited layer, and thus improving the electroplating uniformity of the composite aluminum foil. Therefore, compared with the prior art, the technical solution disclosed in the present invention can significantly improve the electroplating uniformity of composite aluminum foil prepared by molten salt electroplating. DETAILED DESCRIPTION

[0021] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0022] In view of the deficiencies in the prior art mentioned in the background technology, a specific embodiment of the present disclosure provides a plating solution for preparing a composite aluminum foil, the plating solution comprising an ionic liquid and an additive, the additive being selected from one or more of nicotinic acid, methyl nicotinate, 3-methylpyridine, benzoic acid, and ethylene glycol.

[0023] By introducing specific additives into the ionic liquid electrodeposition system, the electrochemical reduction potential of the active species can be changed, thereby affecting the electrochemical crystallization process of the grains, significantly improving the microstructure and properties of the deposited layer, and thus improving the electroplating uniformity of the composite aluminum foil.

[0024] In one embodiment of the present invention, the content of the above additives may be in the range of 1 to 20 mmol / L, preferably 1 to 15 mmol / L, more preferably 10 to 15 mmol / L, based on the total volume of the electroplating solution. A reasonable concentration of the additive can optimize the electroplating process and improve the uniformity of the aluminum layer.

[0025] In a further embodiment of the present invention, the ionic liquid in the plating solution comprises anhydrous aluminum chloride and an organic salt, and the molar ratio of anhydrous aluminum chloride to the organic salt is 1 to 3:1, wherein the organic salt is one or more selected from bromoethylpyridine, n-butylpyridinium chloride, 1-ethyl-3-methylimidazole chloride, urea and acetamide.

[0026] For example, the molar ratio of anhydrous aluminum chloride to the organic salt in the ionic liquid is 1-2.5:1, 1-2:1, more specifically 1:1, 1.5:1, 2:1, 2.5:1 or 3:1.

[0027] The present invention adopts an ionic liquid containing anhydrous aluminum chloride and the above organic salt in a molar ratio of 1 to 3:1, which is beneficial to improving the bonding force between the electroplated aluminum layer and the polymer substrate, accelerating the deposition speed, effectively improving the production efficiency, and facilitating large-scale production.

[0028] Another specific embodiment of the present invention provides a method for preparing a composite aluminum foil, which uses the above-mentioned electroplating solution to prepare the composite aluminum foil. The method of the present invention uses an electroplating solution introduced with specific additives, that is, by introducing one or more of nicotinic acid, methyl nicotinate, 3-methylpyridine, benzoic acid, and ethylene glycol into the ionic liquid electrodeposition system, which can change the electrochemical reduction potential of the active species, thereby affecting the electrochemical crystallization process of the grains, significantly improving the microstructure and performance of the deposited layer, and thus improving the electroplating uniformity of the composite aluminum foil.

[0029] In a specific embodiment of the present invention, the above method includes the following steps: Step S1: Pretreatment of polymer substrate: providing a polymer substrate, and performing surface modification on at least one surface of the polymer substrate by corona treatment or chemical etching solution to obtain a surface-modified polymer substrate; Step S2: Preparation of conductive layer: covering the above at least one surface of the surface-modified polymer substrate with a conductive material by chemical plating or coating or vapor deposition to obtain a polymer substrate covered with a conductive layer; Step S3: Aluminum layer plating: placing the polymer substrate covered with a conductive layer in the electroplating solution of the present invention, depositing an aluminum layer on the surface of the conductive layer away from the polymer substrate by electroplating, and performing heating and pressurization treatment to obtain a composite aluminum foil, wherein the heating range of the heating and pressurization treatment is 30 to 65°C, the pressurization range is 0.2 to 20 MPa, and the treatment time is 0.5 to 60 min.

[0030] The heating range here refers to the target temperature range of the heating treatment, and the pressurization range refers to the target pressure range of the pressurization treatment. The heating and pressurization treatment is intended to control the obtained aluminum layer and polymer substrate within the above-mentioned temperature and pressure range. Specifically, the heating range is 30 to 65°C, preferably 30 to 60°C, and more preferably 40 to 50°C; the pressurization range is 0.2 to 20MPa, preferably 1 to 18MPa, more preferably 5 to 15MPa, and even more preferably 10 to 12MPa. The treatment time is 0.5 to 60min, preferably 3 to 55min, particularly preferably 10 to 50min, and more preferably 20 to 40min.

[0031] The present invention can improve the density of the aluminum layer and further improve the structural uniformity by performing the above-mentioned heating and pressurizing treatment after the aluminum layer is prepared.

[0032] At the same time, in the method of the present invention, by pre-treating the polymer substrate with corona treatment or chemical etching solution before the subsequent conductive layer and electroplating layer are implemented, a roughening effect can be achieved on the surface of the polymer substrate, and hydrophilic groups can be generated on the surface of the polymer substrate, thereby improving the interface bonding strength between the polymer substrate and the subsequent conductive layer and aluminum layer.

[0033] In the method of the present invention, the uniformity of the electroplated aluminum layer can be further improved by controlling the temperature range of the electroplating solution. Specifically, the temperature range of the electroplating solution can be controlled to be 15 to 55° C., preferably 15 to 35° C., and particularly preferably 20 to 30° C. Appropriate control of the temperature of the electroplating solution can enable the ionic liquid and the additive to function efficiently and stably, which is beneficial to further improve the uniformity and density of the aluminum layer.

[0034] In step S2 of the above method of the present invention, after covering the conductive material, heating and pressurization treatment can also be carried out. The heating range of the heating and pressurization treatment in step S2 is 30-65°C, the pressurization range is 0.2-20MPa, and the treatment time is 0.5-60min. The heating range here also refers to the target temperature range of the heating treatment, and the pressurization range also refers to the target pressure range of the pressurization treatment. Through the heating and pressurization treatment, it is intended to control the obtained conductive material layer and the covered polymer substrate within the above temperature and pressure range. Specifically, the heating range is 30-65°C, preferably 30-60°C, and more preferably 40-50°C; the pressurization range is 0.2-20MPa, preferably 1-18MPa, more preferably 5-15MPa, and even more preferably 10-12MPa. The treatment time is 0.5-60min, preferably 3-55min, particularly preferably 10-50min, and preferably 20-40min. By also performing heating and pressurization treatment after the preparation of the conductive layer is completed, the uniformity of the composite aluminum foil structure can be further improved.

[0035] In order to achieve better electroplating uniformity, a preferred embodiment of the present invention further comprises step S4 after step S3: post-plating cleaning. Specifically, in step S4, the obtained composite aluminum foil is placed in an organic cleaning solution for cleaning, and the organic cleaning solution preferably includes one or more selected from ethyl acetate, acetonitrile, ethanol and ethylene glycol. More preferably, the organic cleaning solution includes ethyl acetate, acetonitrile or ethylene glycol. The cleaning is preferably immersion cleaning.

[0036] By introducing an organic cleaning liquid to clean the composite aluminum foil, not only can the uniformity of the aluminum layer be further improved, but also the corrosion of the composite aluminum foil by the residual ionic liquid can be prevented, and the damage to the aluminum layer caused by reactions such as heat release and bubbling during the cleaning process can be avoided.

[0037] From the perspective of economy and cleaning cleanliness, the cleaning time is preferably 30 to 300 seconds. For example, the cleaning time can be 30 seconds, 40 seconds, 50 seconds, 60 seconds, 70 seconds, 80 seconds, 90 seconds, 100 seconds, 110 seconds, 120 seconds, 130 seconds, 140 seconds, 150 seconds, 160 seconds, 170 seconds, 180 seconds, 190 seconds, 200 seconds, 210 seconds, 220 seconds, 230 seconds, 240 seconds, 250 seconds, 260 seconds, 270 seconds, 280 seconds, 290 seconds or 300 seconds.

[0038] The present invention also unexpectedly found that the uniformity of the aluminum layer can be further improved by gradient voltage increase during the electroplating of the aluminum layer. Specifically, in step S3, electroplating is performed under a gradually increasing voltage, wherein the voltage is controlled to increase from an initial value in the range of 0 to 10 V to 5 to 35 V at a rate of 0.5 to 25 V / min. Preferably, the voltage increase rate is controlled at 1 to 20 V / min, more preferably 5 to 15 V / min. By gradient voltage increase, the deposition rate of the aluminum layer can be effectively adjusted to obtain a dense and uniform aluminum layer.

[0039] In some embodiments of the present invention, in the step of pre-treating the polymer substrate, the temperature of the pre-treatment of the polymer substrate is 18-60°C, and the treatment time is 10-200s. For example, the treatment temperature is 18°C, 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc., and the treatment time is 10s, 20s, 30s, 40s, 50s, 60s, 70s, 80s, 90s, 100s, 110s, 120s, 130s, 140s, 150s, 160s, 170s, 180s, 190s, 200s, etc. The treatment temperature and treatment time of the polymer substrate within the scope of the present disclosure can help accelerate the speed of surface pretreatment of the polymer substrate, facilitate the roughening reaction of the polymer substrate surface and the formation of hydrophilic groups, thereby further improving the interface bonding strength between the organic polymer substrate and the subsequently plated or coated conductive layer and aluminum layer, and improving the yield rate.

[0040] In some embodiments of the present invention, in the step of preparing the conductive layer, the temperature of covering the conductive layer is 18-60°C, and the covering time is 40-300s. For example, the covering temperature is 18°C, 20°C, 22°C, 24°C, 26°C, 28°C, 30°C, 32°C, 34°C, 36°C, 38°C, 40°C, 42°C, 44°C, 46°C, 48°C, 50°C, 52°C, 54°C, 56°C, 58°C, 60°C, etc., and the covering time is 40s, 50s, 60s, 70s, 80s, 90s, 100s, 150s, 200s, 250s, 260s, 270s, 280s, 290s, 300s, etc. The temperature and covering time of the conductive layer are within the scope of the present disclosure, which can help to further accelerate the covering rate of the conductive layer, thereby further improving the yield production efficiency.

[0041] In some embodiments of the present invention, in the step of aluminum layer plating, the deposition time (electroplating time) in the aluminum layer plating is 4 to 30 minutes, preferably 5 to 20 minutes, and more preferably 6 to 10 minutes. For example, the deposition time is 4 minutes, 5 minutes, 6 minutes, 7 minutes, 8 minutes, 9 minutes, 10 minutes, 11 minutes, 12 minutes, 13 minutes, 14 minutes, 15 minutes, 16 minutes, 17 minutes, 18 minutes, 19 minutes, 20 minutes, 21 minutes, 22 minutes, 23 minutes, 24 minutes, 25 minutes, 26 minutes, 27 minutes, 28 minutes, 29 minutes, 30 minutes, etc. The aluminum layer deposition time is within the scope of the present disclosure, and the interface bonding force between the aluminum layer and the front cladding layer can be further improved.

[0042] In step S2, the chemical plating solution used in the chemical plating of the conductive layer may include chloroauric acid, sodium carbonate and formaldehyde, or may include nickel sulfate, sodium hypophosphite, trisodium citrate and sodium acetate. For example, the chemical plating solution is prepared from chloroauric acid, sodium carbonate, formaldehyde and deionized water.

[0043] In a further embodiment of the present invention, in step S1, the polymer substrate is one selected from polyethylene terephthalate, polypropylene, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyamide, polyimide, polyoxymethylene, poly-p-phenylene sulfide, poly-p-phenylene oxide and polyethylene glycol. The above are only examples of polymer substrates that can be used in the present application, but the polymer substrate is not limited thereto.

[0044] In a further embodiment of the present invention, in step S1, the chemical etching solution is an aqueous solution containing one or more of sulfuric acid, potassium permanganate, potassium dichromate, chloric acid, sodium hydroxide, nitric acid and hydrogen peroxide. The use of the above chemical etching solution is conducive to further improving the roughening and activation efficiency of the polymer substrate surface, and helps to further improve the formation of hydrophilic groups on the polymer substrate surface, thereby further improving the interface bonding force between the polymer substrate and the subsequent conductive layer and aluminum layer, and further improving the yield and production efficiency.

[0045] In a further embodiment of the present invention, in step S2, the conductive material is one or more selected from carbon, copper, aluminum, nickel, silver, gold and graphene. Graphene is, for example, graphene conductive glue. The conductive material within this range can better impart good conductivity to the polymer substrate, thereby providing better conditions for subsequent metal electroplating.

[0046] In a further embodiment of the present invention, the method is carried out continuously or discontinuously. Those skilled in the art can choose to carry out the method continuously or discontinuously as needed.

[0047] Preferably, the method is carried out continuously. More preferably, step S1, step S2 and step S3 are carried out continuously in a roll-to-roll manner, and the winding speeds of step S1, step S2 and step S3 are each in the range of 1 to 50 m / min and the winding speeds of the three are the same.

[0048] In some preferred embodiments of the present invention, in the composite aluminum foil, the thickness D1 of the polymer substrate satisfies: 1 μm≤D1≤20 μm; the thickness D2 of the conductive layer satisfies: 10 nm≤D2≤1000 nm; and the thickness D3 of the aluminum layer satisfies: 1 μm≤D3≤10 μm.

[0049] The polymer substrate pretreatment step, the conductive layer preparation step and the aluminum layer plating step of the present invention are carried out in a roll-to-roll manner, so that the polymer substrate pretreatment, the conductive layer preparation and the aluminum layer plating can be carried out continuously. The roll-to-roll production method can save the interruption, shifting, placement and waiting process between each link, and can improve production efficiency while avoiding problems such as surface oxidation, deactivation and increased internal stress of the material caused by long-term placement, thereby further improving the product yield, improving production efficiency, and facilitating large-scale production.

[0050] According to another embodiment of the present invention, a composite aluminum foil prepared by the above method is provided, wherein the composite aluminum foil has improved uniformity of the aluminum layer.

[0051] According to the above-mentioned embodiments of the present disclosure, a plating solution, an electroplating method and a composite aluminum foil prepared thereby are provided that can improve the uniformity of electroplating of a composite aluminum foil. In the present invention, by introducing a specific type of additive into the ionic liquid electrodeposition system, the electrochemical reduction potential of the active species can be changed, thereby affecting the electrochemical crystallization process, significantly improving the microstructure and performance of the deposited layer, and ultimately improving the uniformity of the aluminum layer. By heating and pressurizing the material after the preparation of the electroplated layer, the density and structural uniformity of the aluminum layer can be further improved. Furthermore, by also performing heating and pressurizing after the preparation of the conductive layer, the uniformity of the composite aluminum foil structure can be further improved. Moreover, by gradually increasing the pressure and controlling the temperature of the plating solution during the electroplating process, the deposition speed and structure of the aluminum layer can be effectively adjusted to obtain a dense and uniform aluminum layer. In addition, by using an organic cleaning solution to clean the composite aluminum foil obtained by electroplating, the density and uniformity of the composite aluminum foil can also be further improved.

[0052] The present application is further described in detail below in conjunction with specific embodiments. These embodiments should not be construed as limiting the scope of protection claimed in the present application.

[0053] Example 1

[0054] (1) Pretreatment of polymer substrate: The polyethylene terephthalate substrate was subjected to corona treatment at 35° C. to obtain a surface-modified polymer substrate.

[0055] (2) Preparation of conductive layer: A silver layer as a conductive layer was prepared on the surface of the surface-modified polymer substrate by chemical plating at a temperature of 35°C, and the polymer substrate covered with the conductive layer was subjected to heating and pressurization treatment, the heating temperature was 50°C, the external pressure was 1.6 MPa, and the heating and pressurization time was 10 min. The chemical plating solution used was prepared from chloroauric acid, sodium carbonate, formaldehyde and deionized water, and the concentration of chloroauric acid in the prepared chemical plating solution was 33 g / L, the concentration of sodium carbonate was 95 g / L, and the concentration of formaldehyde was 60 mL / L.

[0056] (3) Aluminum electroplating: In an argon atmosphere, the polymer substrate covered with a silver layer is used as the cathode, the high-purity aluminum plate is used as the anode, and the electroplating solution is used as the electrolyte. The aluminum electroplating treatment is carried out at a temperature of 35°C for 6 minutes. The electroplating solution is prepared from anhydrous aluminum chloride, acetamide, and nicotinic acid. The molar ratio of anhydrous aluminum chloride: acetamide used in the preparation is 1.5:1, and the concentration of nicotinic acid is 4mmol / L. The electroplating is carried out at a gradually increasing voltage, and the voltage is controlled to increase from 5V to 15V at a rate of 5V / min. After electroplating, a heating and pressurizing treatment is carried out, the heating temperature is 50°C, the external pressure is 1.6MPa, and the heating and pressurizing time is 10min to obtain a composite aluminum foil.

[0057] (4) Post-plating cleaning: The composite aluminum foil was placed in ethyl acetate for immersion cleaning at 35°C for 40 seconds.

[0058] Example 2

[0059] (1) Pretreatment of polymer substrate: The polyimide substrate is chemically etched with a sodium hydroxide solution at a temperature of 20° C. to obtain a surface-modified polymer substrate. The chemical etching solution is prepared from sodium hydroxide and deionized water. In the prepared chemical etching solution, the concentration of sodium hydroxide is 50 g / L.

[0060] (2) Preparation of conductive layer: An aluminum layer as a conductive layer is prepared by magnetron sputtering on a surface-modified polymer substrate at a temperature of 20°C. The surface-modified polymer substrate is then subjected to heating and pressurization treatment at a heating temperature of 30°C, an external pressure of 20 MPa, and a heating and pressurization time of 3 min to obtain a polymer substrate covered with a conductive layer.

[0061] (3) Aluminum electroplating: In an argon atmosphere, the polymer substrate covered with the aluminum layer is used as the cathode, the high-purity aluminum plate is used as the anode, and the electroplating solution is used as the electrolyte. The aluminum electroplating treatment is carried out at a temperature of 20°C for 10 minutes. The electroplating solution is prepared from anhydrous aluminum chloride, bromoethylpyridine, and ethylene glycol. The molar ratio of anhydrous aluminum chloride: acetamide used in the preparation is 1:1, and the concentration of ethylene glycol is 20mmol / L. The electroplating is carried out at a gradually increasing voltage, and the control voltage is increased from 8V to 20V at a rate of 0.5V / min. After electroplating, a heating and pressurizing treatment is carried out, the heating temperature is 30°C, the external pressure is 20MPa, and the heating and pressurizing time is 3min to obtain a composite aluminum foil.

[0062] (4) Post-plating cleaning: The composite aluminum foil was placed in acetonitrile for immersion cleaning at 20°C for 60 seconds.

[0063] Example 3

[0064] (1) Pretreatment of polymer substrate: The polyethylene terephthalate substrate was chemically etched with a potassium permanganate-sulfuric acid solution at a temperature of 55° C. to obtain a surface-modified polymer substrate. The chemical etching solution was prepared from potassium permanganate, sulfuric acid and deionized water. In the prepared chemical etching solution, the concentration of potassium permanganate was 100 g / L and the concentration of sulfuric acid was 200 g / L.

[0065] (2) Preparation of conductive layer: A carbon layer as a conductive layer was prepared by coating on the surface of the surface-modified polymer substrate at a temperature of 55° C. Then, the polymer substrate covered with the conductive layer was subjected to heating and pressurization treatment at a heating temperature of 65° C., an external pressure of 0.2 MPa, and a heating and pressurization time of 20 min.

[0066] (3) Aluminum electroplating: In an argon atmosphere, the polymer substrate covered with a carbon layer is used as the cathode, the high-purity aluminum plate is used as the anode, and the electroplating solution is used as the electrolyte. The aluminum electroplating treatment is carried out at a temperature of 55°C for 4 minutes. The electroplating solution is prepared from anhydrous aluminum chloride, 1-ethyl-3-methylimidazole chloride, and benzoic acid. The molar ratio of anhydrous aluminum chloride: 1-ethyl-3-methylimidazole chloride used in the preparation is 3:1, and the concentration of benzoic acid is 1mmol / L. Electroplating is carried out at a gradually increasing voltage, and the voltage is controlled to increase from 0V to 25V at a rate of 25V / min. After electroplating, heating and pressurization treatment is carried out, the heating temperature is 65°C, the external pressure is 0.2MPa, and the heating and pressurization time is 20min to obtain a composite aluminum foil.

[0067] (4) Post-plating cleaning: The composite aluminum foil was placed in ethylene glycol for immersion cleaning at 55°C for 300 seconds.

[0068] Example 4

[0069] The composite aluminum foil was prepared in the same manner as in Example 1, except that the additive nicotinic acid was replaced by methyl nicotinate.

[0070] Example 5

[0071] The composite aluminum foil was prepared in the same manner as in Example 1, except that the additive nicotinic acid was replaced by 3-methylpyridine.

[0072] Example 6

[0073] The composite aluminum foil was prepared in the same manner as in Example 1, except that the heating and pressurizing treatment in the conductive layer preparation step was omitted.

[0074] Example 7

[0075] The composite aluminum foil was prepared in the same manner as in Example 1, except that the heating and pressurizing treatments in the steps of preparing the conductive layer and electroplating aluminum were omitted.

[0076] Example 8

[0077] The composite aluminum foil was prepared in the same manner as in Example 1, except that a constant voltage of 15 V was applied during electroplating of the aluminum layer instead of applying it in a gradually increasing manner.

[0078] Example 9

[0079] The composite aluminum foil was prepared in the same manner as in Example 1, except that the cleaning solution was replaced with deionized water.

[0080] Comparative Example 1

[0081] The composite aluminum foil was prepared in the same manner as in Example 1, except that no additive component was included in the electroplating solution.

[0082] Comparative Example 2

[0083] The composite aluminum foil is prepared in the same manner as in Example 9, except that there is no additive component in the plating solution.

[0084] Performance Testing

[0085] Determination of surface resistance

[0086] The surface square resistance was measured using a four-probe square resistance meter at a temperature of 25°C. During the test, five different areas were selected on the surface of the sample for square resistance testing, and the square resistance range was calculated to determine the uniformity of the composite aluminum foil.

[0087] Table 1

[0088]

[0089]

[0090] Comparing Examples 1-5 with Comparative Example 1, the uniformity of the electroplated aluminum foil can be significantly improved by introducing the additive of the present invention into the electroplating solution. Comparing Example 9 with Comparative Example 2, it can also be seen that the use of the additive can significantly improve the uniformity of the electroplated aluminum foil.

[0091] By comparing Example 1 with Examples 6 and 7, it can be found that the heating and pressurizing treatment in the method of the present invention can further improve the uniformity of the electroplated aluminum foil to a certain extent. By comparing Example 1 with Example 8, it can be seen that the use of a gradient boost method in the electroplating process of the present invention can further improve the uniformity of the electroplated aluminum foil. By comparing Example 1 with Example 9, it can be found that the use of an organic cleaning solution in the cleaning step of the present invention can further improve the uniformity of the electroplated aluminum foil to a certain extent compared to the use of deionized water.

[0092] The results of the embodiments prove that the technical solution of the present invention has the following beneficial effects:

[0093] - By introducing additives into the ionic liquid electrodeposition system, the electrochemical reduction potential of the active species can be changed, thereby affecting the electrochemical crystallization process of the grains, which can significantly improve the microstructure and performance of the deposited layer;

[0094] - After the conductive layer and electroplating layer are prepared, the density and structural uniformity of each layer can be further improved;

[0095] -By increasing the voltage gradually during the electroplating process, the deposition speed and structure of the aluminum layer can be adjusted to obtain a dense and uniform aluminum layer;

[0096] -The uniformity of the aluminum layer can be further improved by using an organic cleaning solution in the cleaning step.

[0097] The above description only relates to specific embodiments of the present disclosure and is not intended to limit the present disclosure. For those skilled in the art, the present disclosure may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. An electroplating solution for preparing a composite aluminum foil, characterized in that: The electroplating solution comprises an ionic liquid and an additive, wherein the additive is selected from one or more of nicotinic acid, methyl nicotinate, 3-methylpyridine, benzoic acid, and ethylene glycol.

2. The electroplating solution according to claim 1, characterized in that The concentration of the additive in the electroplating solution is 1-20 mmol / L.

3. The electroplating solution according to claim 1 or 2, characterized in that: The ionic liquid comprises anhydrous aluminum chloride and an organic salt, wherein the molar ratio of the anhydrous aluminum chloride to the organic salt is 1 to 3:1; and the organic salt is selected from one or more of bromoethylpyridine, n-butylpyridinium chloride, 1-ethyl-3-methylimidazole chloride, urea and acetamide.

4. A method for preparing a composite aluminum foil, characterized in that: The method adopts the electroplating solution according to any one of claims 1 to 3 to prepare the composite aluminum foil.

5. The method according to claim 4, characterized in that The method comprises the following steps: Step S1: pretreatment of polymer substrate: providing a polymer substrate, and performing surface modification on at least one surface of the polymer substrate by corona treatment or chemical etching solution to obtain a surface-modified polymer substrate; Step S2: preparing a conductive layer: covering the at least one surface of the surface-modified polymer substrate with a conductive material by chemical plating, coating or vapor deposition to obtain a polymer substrate covered with a conductive layer; Step S3: Aluminum layer plating: placing the polymer substrate covered with the conductive layer in the electroplating solution, depositing an aluminum layer on the surface of the conductive layer away from the polymer substrate by electroplating, and performing heating and pressurization treatment to obtain the composite aluminum foil, wherein the heating range of the heating and pressurization treatment is 30 to 65°C, the pressurization range is 0.2 to 20 MPa, and the treatment time is 0.5 to 60 min.

6. The method according to claim 5, characterized in that In step S3, the temperature of the electroplating solution is controlled to be in the range of 15 to 55°C.

7. The method according to claim 5, characterized in that In the step S2, after covering the conductive material, heating and pressurizing treatment is performed to obtain the polymer substrate covered with the conductive layer. The heating range of the heating and pressurizing treatment in the step S2 is 30-65° C., the pressurizing range is 0.2-20 MPa, and the treatment time is 0.5-60 min.

8. The method according to any one of claims 5 to 7, characterized in that: The method further comprises, after step S3: Step S4: Post-plating cleaning: placing the composite aluminum foil in an organic cleaning solution for cleaning, wherein the organic cleaning solution comprises one or more selected from ethyl acetate, acetonitrile, ethanol and ethylene glycol.

9. The method according to any one of claims 5 to 7, characterized in that: In the step S3, the electroplating is performed under a gradually increasing voltage, wherein the voltage is controlled to increase from an initial value in the range of 0 to 10 V to 5 to 35 V at a rate of 0.5 to 25 V / min.

10. A composite aluminum foil, characterized in that: The composite aluminum foil is prepared by the method according to any one of claims 4 to 9.

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