Aluminum foil and its preparation method and application

Abstract

Aluminum foil, its preparation method, and application belong to the field of electrochemical technology. The present invention comprises the following steps: inserting a cathode, an anode, and a reference electrode into a chloroaluminate-type ionic liquid to form a three-electrode system, wherein the cathode is titanium, the anode is aluminum or an aluminum alloy, the reference electrode is aluminum, and the chloroaluminate-type ionic liquid contains water. The chloroaluminate-type ionic liquid is heated to 35-70°C, a voltage of 2-7V is applied between the anode and the reference electrode, and aluminum foil is produced on the cathode. The present invention produces aluminum foil by electrorefining within this voltage range by applying a voltage of 2-7V between the anode and the reference electrode, which is higher than the electrolysis voltage for anode passivation and lower than the voltage for deterioration and decomposition of the ionic liquid.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrochemistry, and in particular relates to an aluminum foil and a preparation method and application thereof. Background Art

[0002] Aluminum foil is lightweight, easy to process, and abundant in resources. It serves as a key component in lithium-ion and sodium-ion batteries. Aluminum foil is primarily produced through rolling technology, which uses aluminum strip to produce foil thicker than 16 μm. The energy consumption for rolling foil to a thickness greater than 16 μm is approximately 2,279 kW·h / ton. This energy consumption rises to approximately 2,652 kW·h / ton for thinner foil (10 μm), resulting in high energy consumption. Furthermore, the physical properties of aluminum easily change during rolling, making it difficult to produce thinner foil using this method.

[0003] Compared with rolling technology, electrorefined aluminum deposition has the potential to produce thinner aluminum foil. Among them, electrorefined aluminum deposition is mainly based on AlCl3 type ionic liquid. In acidic ionic liquid (AlCl3 mole fraction greater than 50%), the electrorefining process of aluminum and aluminum alloys is as follows:

[0004] Anode: Al+7AlCl4 - -3e - →4Al2Cl7 - (acidic)

[0005] Cathode: 4Al2Cl7 - +3e - →Al+7AlCl4 -

[0006] Overall reaction: Al (or aluminum alloy) → Al (pure aluminum)

[0007] However, the electrorefining process of aluminum and aluminum alloys in ionic liquids is often hampered by the phenomenon of anodic passivation, which prevents it from being scaled up for practical application. Anodic passivation usually occurs when the potential and anion concentration change during metal dissolution. When passivation occurs, anodic dissolution decreases or stops, and the refining process cannot continue. Currently, researchers have found that the passivation phenomenon is caused by the consumption of AlCl4 by aluminum dissolution at high anodic potential. - Generates a large amount of Al2Cl7 - , the concentration change leads to Al2Cl7 - →AlCl3+AlCl4 - The reaction occurs, forming a solid AlCl3 insulating layer on the anode surface. Consequently, at high anode potentials, anode passivation occurs, and the refining process cannot continue. Furthermore, AlCl3 ionic liquids are generally water-averse.

[0008] In summary, almost all current studies on the electrorefining of aluminum and aluminum alloys in ionic liquids control the anode potential below the passivation potential, and in order to prevent the generation of HF or HCl and O induced by water, the anode potential should be kept below the passivation potential.2- Ions cause ionic liquids to deteriorate, and almost all electrorefining processes of aluminum or aluminum alloys in ionic liquids are used in oxygen-free and water-free environments. These two bottlenecks limit the promotion and application of electrorefining technology of aluminum and aluminum alloys in ionic liquids. Summary of the Invention

[0009] In view of the above-mentioned shortcomings, the present invention provides an aluminum foil and a preparation method and application thereof. The preparation method can produce aluminum foil by electrorefining in an oxygen and water environment.

[0010] A first aspect of the present invention provides a method for preparing an aluminum foil, comprising the following steps:

[0011] Inserting a cathode, an anode, and a reference electrode into a chloroaluminate-type ionic liquid to form a three-electrode system, wherein the cathode is titanium, the anode is aluminum or an aluminum alloy, the reference electrode is aluminum, and the chloroaluminate-type ionic liquid contains water;

[0012] The chloroaluminate-type ionic liquid is heated to 35-70° C., a voltage of 2-7 V is applied between the anode and the reference electrode, and an aluminum foil is formed on the cathode.

[0013] Furthermore, the chloroaluminate-type ionic liquid is selected from [Emim]Cl-AlCl3 ionic liquid, TMPAC-AlCl3 ionic liquid, TMBAC-AlCl3 ionic liquid, BMIC-AlCl3 ionic liquid, choline chloride-urea-AlCl3 ionic liquid, MMPIM-AlCl3 ionic liquid or TEBAC.

[0014] Furthermore, the voltage is applied for 10 to 60 minutes to generate the aluminum foil.

[0015] Furthermore, the molar ratio of the solute to the solvent in the chloroaluminate-type ionic liquid is 2-3:1.

[0016] Furthermore, the chloroaluminate-type ionic liquid is heated to 40-50°C.

[0017] Furthermore, a stirring element is provided in the chloroaluminate-type ionic liquid, and the rotation speed of the stirring element is 300-900 r / min.

[0018] The present invention protects the aluminum foil prepared by the above preparation method, and the thickness of the aluminum foil is 2-3 μm.

[0019] The third aspect of the present invention protects the use of the above-mentioned aluminum foil in a current collector.

[0020] Beneficial Effects: The present invention applies a voltage of 2-7V between the anode and the reference electrode. This voltage is higher than the electrolysis voltage at which the anode is passivated and lower than the voltage at which the ionic liquid deteriorates and decomposes. Within this voltage range, aluminum foil is electrorefined to form aluminum foil. During the electrolysis process, the AlCl3 content is always greater than the organic cation content to ensure that the ionic liquid is acidic. The chemical reactions involved are: Titanium sheet cathode: 4Al2Cl7 - +3e - =Al+7AlCl4 - ; Aluminum anode: Al+7AlCl4 - →4Al2Cl7 - +3e - During the low-potential anodic dissolution process, a solid AlCl3 passivation layer is formed on the surface of the aluminum electrode due to the concentration change of the active substance in the electrolyte, which makes the deposition reaction unable to proceed for a long time. 2- , which will occur during the passivation process (low potential area) 2- + 2AlCl4 - + Al→ AlOCl(s) + Al2Cl7 - + 3e - , forming AlOCl passivation film; while in the high potential area, 13AlCl4 - + AlCl3(s) + Al+ AlOCl(s) → O 2- + 8Al2Cl7 - + 3e - The reaction dissolves the passivation film. This converts the AlCl3 passivation film produced in the low-potential region into an AlOCl film. Further increasing the potential dissolves the AlOCl, ensuring that the deposition reaction can proceed for a long time and eliminating the effects of anodic passivation. The essence of the present invention is to convert the AlCl3 passivation film into an AlOCl passivation film through a combination of electrochemical and chemical methods, and then remove the AlOCl, thereby resolving the anodic passivation problem that exists during the reaction process and providing theoretical support for the industrialization of ionic liquid aluminum deposition. DETAILED DESCRIPTION

[0021] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making any creative efforts are within the scope of protection of the present invention.

[0022] A first aspect of the present invention provides a method for preparing an aluminum foil, comprising the following steps:

[0023] Step 1: Insert a cathode, an anode, and a reference electrode into a chloroaluminate-type ionic liquid to form a three-electrode system, wherein the cathode is titanium, the anode is aluminum or an aluminum alloy, and the anode can also be selected from scrap aluminum. Selecting scrap aluminum can reuse the scrap aluminum and save resources. The reference electrode is aluminum, and the chloroaluminate-type ionic liquid contains water.

[0024] Step 2: Heat the chloroaluminate-type ionic liquid to 35-70° C., apply a voltage of 2-7 V between the anode and the reference electrode, and generate aluminum foil on the cathode.

[0025] In the actual production process, a small amount of O 2- Ions exist, containing O 2- Ionic liquids are a common practice.

[0026] Based on the above actual situation, the present invention proposes a method for preparing aluminum foil, that is, in the presence of O 2- In the anodic process of ionic liquids, there is A:O 2- + 2AlCl4 - + Al → AlOCl(s) + Al2Cl7 - + 3e and B: 13AlCl4 - + AlCl3(s)+ Al + AlOCl(s) → O 2- + 8Al2Cl7 - + 3e - The present invention controls the anode potential of aluminum or aluminum alloy to be higher than the electromotive force of the above-mentioned B reaction, thereby ensuring that the anode continuously dissolves and aluminum foil continuously deposits on the cathode.

[0027] In a specific embodiment, the chloroaluminate-type ionic liquid is selected from [Emim]Cl-AlCl3 ionic liquid, TMPAC (trimethylphenylammonium chloride)-AlCl3 ionic liquid, TMBAC (benzyltrimethylammonium chloride)-AlCl3 ionic liquid, BMIC (1-butyl-3-methylimidazolium chloride)-AlCl3 ionic liquid, choline chloride-urea-AlCl3 ionic liquid, MMPIM-AlCl3 ionic liquid or TEBAC (triethylbenzylammonium chloride).

[0028] In a specific embodiment, the method for preparing the aluminum foil in this embodiment specifically includes the following steps:

[0029] Step 1-1: Prepare O 2-Ionic liquid. EMIC and anhydrous AlCl3 were weighed separately in a molar ratio of 1:2. Anhydrous AlCl3 was slowly added to EMIC and magnetically stirred at 30-50°C until it was completely converted into a liquid. Pure aluminum wire was immersed in the [Emim]Cl-AlCl3 ionic liquid to remove impurities. The wire was then placed in an argon or nitrogen atmosphere (H2O, 2×10 - 5 mg / L) in a glove box. The remaining ionic liquids were prepared in the same manner and placed in the glove box.

[0030] Among them, after the ionic liquid is prepared, it is sealed with plastic wrap and stored; the aluminum wire used for purification is spiral to increase the contact area, and the refining time is more than 7 days.

[0031] The refined ionic liquids were placed for three months to allow them to fully absorb the residual H2O in the glove box and deteriorate (O 2- increase).

[0032] Step 1-2: Prepare the electrodes. Cut aluminum, aluminum alloy, and titanium into appropriate sizes. Grind the electrode materials (99.99% purity, Sinopharm Chemical Reagent Company) with fine sandpaper and polish in a NaOH solution. Connect the electrodes to copper wires to create the electrodes. Separately, prepare a 2mm diameter aluminum wire as a reference electrode. Ultrasonicate all electrodes in an ultrasonic bath for 3-5 minutes using deionized water. Quickly air dry and transfer to a glove box. Separately, prepare a 2mm diameter aluminum wire and various aluminum alloy wires. Grind them with sandpaper, clean, and dry them. Seal the surrounding area with epoxy resin, exposing the circular cross-section, and transfer to a glove box.

[0033] The specifications of the anode are preferably 0.2*20*20mm; the specifications of the cathode are preferably 0.2*20*20mm; and the specifications of the reference electrode are preferably φ2mm;

[0034] The area of ​​the circular cross section is πmm 2 The purpose of using epoxy resin sealing is to ensure that the anode area remains constant during the test.

[0035] Step 2-1: Anodic Dissolution Potential Measurement. Insert the cathode, an epoxy-sealed aluminum / aluminum alloy wire, and a reference electrode into the [Emim]Cl-AlCl₃ ionic liquid at 30-70°C. Measure the anodic dissolution potential using cyclic voltammetry at a potential range of -0.8-5 V and a scan rate of 10-100 mV / s. The testing method for different Al alloys and different types of ionic liquids is the same as that for pure Al anodes.

[0036] Step 2-2: Prepare aluminum foil. Based on the anodic dissolution potential measured above, insert a cathode Ti plate, Al or Al alloy plate, and a 2mm diameter aluminum wire into the ionic liquid at 30-70°C, ensuring that the cathode and anode areas are equal. Apply a constant voltage and electro-refine the aluminum foil for 10-60 minutes.

[0037] Step 2-3: Post-processing: Remove the cathode and place it in acetonitrile to wash away any remaining electrolyte. After removing it from the glove box, rinse it again with alcohol to remove any remaining acetonitrile. Peel off the aluminum foil and place it in a sealed bag to prevent oxidation.

[0038] In a specific embodiment, the molar ratio of the solute to the solvent in the chloroaluminate-type ionic liquid is 2-3:1.

[0039] In a specific embodiment, the chloroaluminate-type ionic liquid is heated to 40-50°C.

[0040] In a specific embodiment, a stirring element is provided in the chloroaluminate-type ionic liquid, and the rotation speed of the stirring element is 300-900 r / min.

[0041] The second aspect of the present invention protects the aluminum foil prepared by the above preparation method.

[0042] A third aspect of the present invention is to protect the use of aluminum foil in current collectors.

[0043] The following are specific examples.

[0044] Example 1

[0045] A method for preparing aluminum foil comprises the following steps:

[0046] 1. Cut a 20mm*20mm 0.2mm thick sheet from the Al plate, punch a hole in the center and connect it to a 2mm diameter copper wire to make the anode. Cut a 20mm*20mm 0.2mm thick titanium sheet from the Ti plate, punch a hole and connect it to the copper wire to make the cathode. Take a 2mm diameter aluminum wire as the reference electrode.

[0047] 2. Weigh 9.0g EMIC in the electrolytic cell and 17.279g AlCl in a clean beaker. 3， Aluminum chloride was slowly added to the electrolytic cell containing EMIC while stirring to form Emim-AlCl3 ionic liquid. The electrolytic cell was placed in a heating mantle, which was then placed in a stirring device. The cathode and anode were inserted 10-15 mm into the ionic liquid and connected to a CHI660e electrochemical workstation. All operations were performed in a glove box.

[0048] 3. Heat the ionic liquid to 50±2°C, insert the cathode, anode, and reference electrode into the ionic liquid to form a three-electrode system, and maintain a constant stirring rate of 600r / min; apply a voltage of 3.0±0.1V between the anode and reference electrodes for electrolysis. Based on the initial current change, it can be determined that it is caused by double-layer charging. As the electrolysis time increases, the current generally stabilizes. After 10-30 minutes of constant voltage electrolysis, stop the electrolysis, remove the cathode from the ionic liquid, wash it with acetonitrile, and place it in a sealed bag. All operations are performed in a glove box.

[0049] 4. The cathode sheet was removed and cleaned by soaking in an alcohol solution. The aluminum foil on the cathode sheet was removed and dried. After SEM testing, its thickness was observed to be 2.5 μm. The slurry was prepared by adding a binder solution pre-dissolved in N-methylpyridone (NMP) to the positive electrode active material and conductive additive, so that the mass ratio of active material (lithium cobalt oxide): conductive additive (carbon black): binder (PVDF) was 8:1:1. The prepared slurry was coated on aluminum foil and vacuum dried at 60-90 ° C for 12 hours, and then heated at 0.7 t cm -2 The cathode was prepared by pressing under a pressure of 100°C. The electrochemical properties of the prepared cathode were evaluated through CV measurements, AC impedance measurements, and constant-current charge-discharge tests. The discharge range of the prepared cathode was the same as that of a battery assembled from aluminum foil produced by a rolling method. Under the same conditions, the cathode exhibited over 50 stable cycles exceeding the battery assembled from aluminum foil produced by the rolling method. Furthermore, the cathode exhibited less energy decay during high-rate discharge, demonstrating significantly superior electrochemical performance to aluminum foil produced by the rolling method.

[0050] Example 2

[0051] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0052] (1) The ionic liquid in step 2 is replaced with TMPAC (trimethylphenylammonium chloride)-AlCl3 ionic liquid;

[0053] The other methods are the same.

[0054] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0055] Example 3

[0056] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0057] (1) The ionic liquid in step 2 is replaced with TMBAC (benzyltrimethylammonium chloride)-AlCl3 ionic liquid;

[0058] The other methods are the same.

[0059] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0060] Example 4

[0061] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0062] (1) The ionic liquid in step 2 is replaced with BMIC-AlCl3 ionic liquid;

[0063] The other methods are the same.

[0064] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0065] Example 5

[0066] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0067] (1) The ionic liquid in step 2 is replaced with choline chloride-urea-AlCl3 ionic liquid;

[0068] The other methods are the same.

[0069] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0070] Example 6

[0071] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0072] (1) The ionic liquid in step 2 is replaced with MMPIM-AlCl3 ionic liquid;

[0073] The other methods are the same.

[0074] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0075] Example 7

[0076] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0077] (1) The Al anode in step 2 is replaced with a 1-series Al alloy;

[0078] The other methods are the same.

[0079] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0080] Example 8

[0081] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0082] (1) The Al anode in step 2 is replaced with a 2-series Al alloy;

[0083] The other methods are the same.

[0084] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0085] Example 9

[0086] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0087] (1) The Al anode in step 2 is replaced with a 3-series Al alloy;

[0088] The other methods are the same.

[0089] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0090] Example 10

[0091] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0092] (1) The Al anode in step 2 is replaced with a 4-series Al alloy;

[0093] The other methods are the same.

[0094] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0095] Example 11

[0096] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0097] (1) The Al anode in step 2 is replaced with a 5-series Al alloy;

[0098] The other methods are the same.

[0099] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0100] Example 12

[0101] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0102] (1) The Al anode in step 2 is replaced with a 6-series Al alloy;

[0103] The other methods are the same.

[0104] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0105] Example 13

[0106] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0107] (1) The Al anode in step 2 is replaced with a 7-series Al alloy;

[0108] The other methods are the same.

[0109] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0110] Example 14

[0111] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0112] (1) The Al anode in step 2 is replaced with an 8-series Al alloy;

[0113] The other methods are the same.

[0114] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0115] Example 15

[0116] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0117] (1) The Al anode in step 2 is replaced with a 9 series Al alloy;

[0118] The other methods are the same.

[0119] The cathode product was analyzed and detected, and the electrochemical performance was similar to that in Example 1.

[0120] Example 16

[0121] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0122] (1) The heating temperature in step 3 is 30° C.

[0123] The other methods are the same.

[0124] The resulting cathode aluminum foil is thinner and has holes on its surface, making it unusable as a current collector for lithium-ion batteries.

[0125] Example 17

[0126] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0127] (1) The heating temperature in step 3 is 70° C.

[0128] The other methods are the same.

[0129] The obtained cathode aluminum foil has good performance, but the energy consumption is increased compared with 50°C.

[0130] Example 18

[0131] A method for preparing aluminum foil is the same as that of Example 2, except that:

[0132] (1) The heating temperature in step 3 is 30° C.

[0133] The other methods are the same.

[0134] The resulting cathode aluminum foil is thinner and has holes on its surface, making it unusable as a current collector for lithium-ion batteries.

[0135] Example 19

[0136] A method for preparing aluminum foil is the same as that of Example 1, except that:

[0137] (1) The heating temperature in step 3 is 70° C.

[0138] The other methods are the same.

[0139] The obtained cathode aluminum foil has good performance, but the energy consumption is increased compared with 50°C.

[0140] Example 20

[0141] A method for preparing aluminum foil is the same as that of Example 3, except that:

[0142] (1) The heating temperature in step 3 is 30° C.

[0143] The other methods are the same.

[0144] The resulting cathode aluminum foil is thinner and has holes on its surface, making it unusable as a current collector for lithium-ion batteries.

[0145] Example 21

[0146] A method for preparing aluminum foil is the same as that of Example 3, except that:

[0147] (1) The heating temperature in step 3 is 70° C.

[0148] The other methods are the same.

[0149] The obtained cathode aluminum foil has good performance, but the energy consumption is increased compared with 50°C.

[0150] Example 22

[0151] A method for preparing aluminum foil is the same as that of Example 4, except that:

[0152] (1) The heating temperature in step 3 is 30° C.

[0153] The other methods are the same.

[0154] The resulting cathode aluminum foil is thinner and has holes on its surface, making it unusable as a current collector for lithium-ion batteries.

[0155] Example 23

[0156] A method for preparing aluminum foil is the same as that of Example 4, except that:

[0157] (1) The heating temperature in step 3 is 70° C.

[0158] The other methods are the same.

[0159] The obtained cathode aluminum foil has good performance, but the energy consumption is increased compared with 50°C.

[0160] Comparative Example 1

[0161] A method for preparing aluminum foil is the same as that in Example 1, except that:

[0162] In step 3, the electrolysis voltage was set to 0.2 V, and the others were the same as in Example 1.

[0163] Using this method, the cathode product aluminum foil cannot be obtained, and the black substance on the anode surface prevents the anode from corroding for a long time. This is because the anode has a passivation reaction at low potential: 4Al2Cl7 - → 7AlCl4 - + AlCl3(s) and O 2- +2AlCl4 - +Al→ AlOCl(s)+Al2Cl7 - +3e - The two processes proceed simultaneously and compete with each other. And because the potential is only 0.2V and the current is small, the cathode product cannot form a dense aluminum foil at low current density.

[0164] Comparative Example 2

[0165] A method for preparing aluminum foil is the same as that in Example 1, except that:

[0166] In step 3, the electrolysis voltage was set to 0.8 V, and the others were the same as in Example 1.

[0167] Using this method, the cathode product aluminum foil cannot be obtained, and the black substance on the anode surface prevents the anode from corroding for a long time.

[0168] Comparative Example 3

[0169] A method for preparing aluminum foil is the same as that in Example 1, except that:

[0170] In step 3, the electrolysis voltage is set to 1.2 V, and the others are the same as in Example 1.

[0171] This method failed to produce aluminum foil as a cathode product, and the black material on the anode surface faded, leaving a gray material that prevented the anode from corroding over time. This is because the passivation film formed at low potential begins to dissolve as the potential increases. Furthermore, because the potential is only 1.2V and the current is low, the cathode product cannot form a dense aluminum foil at low current density.

[0172] Comparative Example 4

[0173] A method for preparing aluminum foil is the same as that in Example 1, except that:

[0174] In step 3, the electrolysis voltage is set to 4 V, and the others are the same as in Example 1.

[0175] This method produced aluminum foil as a cathode product, and the black material on the anode surface faded, revealing a corroded, shiny state. This was because the passivation film formed at high potential dissolved as the potential increased. The resulting aluminum foil had excellent electrochemical properties, similar to those in Example 1. Energy consumption was increased.

[0176] Comparative Example 5

[0177] A method for preparing aluminum foil is the same as that in Example 1, except that:

[0178] In step 3, the electrolysis voltage is set to 7V, and the others are the same as in Example 1.

[0179] This method produced aluminum foil as a cathode product, and the black material on the anode surface faded, revealing a corroded, shiny state. This was because the passivation film formed at high potential dissolved as the potential increased. The resulting aluminum foil had excellent electrochemical properties, similar to those in Example 1. Energy consumption was increased.

[0180] Comparative Example 6

[0181] A method for preparing aluminum foil is the same as that in Example 1, except that:

[0182] In step 3, the electrolysis voltage is set to 10 V, and the others are the same as in Example 1.

[0183] When this method is used, if the electrochemical window voltage of the ionic liquid is exceeded, the ionic liquid deteriorates, no product can be obtained, and harmful gases are generated.

[0184] Comparative Example 7

[0185] A method for preparing aluminum foil is similar to Example 1, except that the ionic liquid is changed to TMPAC (trimethylphenylammonium chloride)-AlCl3 ionic liquid, TMBAC (benzyltrimethylammonium chloride)-AlCl3 ionic liquid, BMIC-AlCl3 ionic liquid, choline chloride-urea-AlCl3 ionic liquid, or MMPIM-AlCl3 ionic liquid. The results are the same as those of Comparative Examples 3-8.

[0186] Comparative Example 8

[0187] A method for preparing aluminum foil, similar to Example 1, differs in that the aluminum foil used in lithium-ion battery assembly is no longer produced by electrorefining scrap aluminum / aluminum alloy, but is replaced with commercially available rolled aluminum foil. Testing revealed that the rate performance and cycle performance of the aluminum foil were inferior to those of the electrorefined aluminum foil.

[0188] The above disclosure is merely a preferred embodiment of the present invention and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention are still within the scope of the present invention.

Claims

1. A method for preparing aluminum foil, characterized in that: The steps include: Inserting a cathode, an anode, and a reference electrode into a chloroaluminate-type ionic liquid to form a three-electrode system, wherein the cathode is titanium, the anode is aluminum or an aluminum alloy, the reference electrode is aluminum, and the chloroaluminate-type ionic liquid contains water; The chloroaluminate-type ionic liquid is heated to 35-70° C., a voltage of 2-7 V is applied between the anode and the reference electrode, and an aluminum foil is formed on the cathode.

2. The method for preparing aluminum foil according to claim 1, wherein The chloroaluminate-type ionic liquid is selected from [Emim]Cl-AlCl3 ionic liquid, TMPAC-AlCl3 ionic liquid, TMBAC-AlCl3 ionic liquid, BMIC-AlCl3 ionic liquid, choline chloride-urea-AlCl3 ionic liquid, MMPIM-AlCl3 ionic liquid or TEBAC.

3. The method for preparing aluminum foil according to claim 1, wherein The voltage is applied for 10 to 60 minutes to generate the aluminum foil.

4. The method for preparing aluminum foil according to claim 1, wherein: The molar ratio of the solute to the solvent in the chloroaluminate-type ionic liquid is 2-3:

1.

5. The method for preparing aluminum foil according to claim 1, wherein: The chloroaluminate-type ionic liquid is heated to 40-50°C.

6. The method for preparing aluminum foil according to claim 1, wherein: A stirring element is provided in the chloroaluminate-type ionic liquid, and the rotation speed of the stirring element is 300-900 r / min.

7. An aluminum foil prepared by the preparation method according to any one of claims 1 to 6.

8. The aluminum foil according to claim 7, characterized in that The thickness of the aluminum foil is 2-3 μm.

9. Use of the aluminum foil prepared by the preparation method according to any one of claims 1 to 6 or the aluminum foil according to any one of claims 7 to 8 in a current collector.