Ultrathin aluminum foil current collector surface wettability regulation and control method and application

Abstract

The invention discloses an ultrathin aluminum foil current collector surface wettability regulation and control method and application. Belongs to the technical field of lithium ion batteries. The invention relates to an ultrathin aluminum foil current collector surface wettability regulation and control method, specifically, the surface of an aluminum foil current collector has a uniform nanopore structure, and the pore diameter is 10-30nm; a polyaniline group is introduced into the surface of the nanopore structure. According to the invention, a uniform nanopore structure with controllable morphology is constructed on the surface of the ultrathin aluminum foil, the pore diameter is 10-30nm, binding sites are provided for lithium iron phosphate particles, and a meshing effect is formed; and the wetting ability between the anode lithium iron phosphate and an aluminum current collector can be further enhanced when the lithium iron phosphate is applied to the anode current collector of the lithium ion battery. According to the current collector, a conductive network is formed between nanopores on the surface of the aluminum foil and a lithium iron phosphate layer through a nanopore structure and in combination with surface-modified chemical polar groups, so that the dosage of a conductive agent in an electrode is remarkably reduced, the corrosion effect of an electrolyte on the aluminum foil is delayed, and the specific capacity and cycling stability of a lithium ion battery are improved.

Description

Technical Field

[0001] The present invention relates to a method for controlling the surface wettability of an ultra-thin aluminum foil current collector and its application, belonging to the technical field of lithium-ion batteries. Background Art

[0002] Aluminum foil has excellent electrochemical stability, conductivity, lightweight, and good mechanical properties. It is used as a positive electrode current collector for lithium-ion batteries. Its function is to carry the positive electrode active material. During the charge and discharge process of the lithium battery, it can gather current and conduct it to the external circuit. It itself does not participate in the electrochemical reaction. Thinning the aluminum foil can not only reduce the weight proportion of inactive materials, directly increase the energy density of the battery, but also reduce the cost of raw materials. At present, the thinnest aluminum foil for lithium-ion battery positive electrode current collectors in commercial mass production can reach 9μm. However, the surface of the aluminum foil obtained through multiple rolling passes is relatively smooth and has poor surface wettability, resulting in poor adhesion when the positive electrode active material is coated and insufficient interfacial bonding strength. During the charge and discharge process, due to the expansion / contraction of the active material particles, it is easy to fall off the current collector, resulting in a decrease in battery capacity and life. In addition, the interface resistance between the aluminum foil and the active material is too large, which will reduce the current transmission efficiency and cause safety problems such as battery thermal runaway.

[0003] Electrochemical etching can roughen the surface of aluminum foil, forming rough structures such as pores and pits. This improves surface wettability and effectively enhances the bonding between the aluminum current collector and the active material. Currently, acidic solutions such as hydrochloric acid, sulfuric acid, nitric acid, hydrofluoric acid, and acetic acid are primarily used as electrolytes. For example, patent 200610172613.9 uses sulfuric acid as the electrolytic etching solution. However, this method poses problems such as environmental pollution and uncontrollable etching levels. Furthermore, electrochemical etching takes a long time and is inefficient. For example, patent CN109148895B still requires 10 to 30 minutes to roughen the aluminum current collector. Furthermore, patent CN111430726B uses AC etching to expand the pores on the aluminum foil surface, achieving an aluminum current collector with a surface pore size distribution of 5 to 10 μm. This allows the positive electrode active material to enter the pores and "mesh" with the aluminum foil during coating, improving bonding and reducing resistance, thereby enhancing the discharge capacity, high-current discharge performance, and cycling performance of lithium-ion batteries. However, for ultra-thin aluminum foil, excessive etching by strong acid electrolyte and the construction of micron-level void structures on the surface can easily lead to uneven etching and perforation of the ultra-thin aluminum foil, ultimately losing its mechanical bearing capacity and affecting battery stability and safety.

[0004] In summary, for ultra-thin aluminum foil current collectors, how to use a mild and environmentally friendly electrochemical etching process to efficiently and stably treat the aluminum foil surface to improve the wettability of the aluminum foil surface is an important issue in improving the current collector performance and promoting the development of the lithium battery industry. Summary of the Invention

[0005] The present invention aims to provide a method for regulating the surface wettability of ultrathin aluminum foil current collectors, addressing technical issues such as poor surface wettability of ultrathin aluminum foil current collectors, low efficiency of conventional electrochemical etching processes, significant environmental pollution, and the tendency for ultrathin aluminum foil perforation. The method provided by the present invention is gentle and environmentally friendly, with high preparation efficiency and strong structural controllability.

[0006] At the same time, the present invention provides an ultra-thin aluminum foil current collector. The ultra-thin aluminum foil current collector prepared by the present invention has a strong bonding force with the active material and can maintain good integrity, which can significantly improve the electrochemical performance and stability of the battery.

[0007] At the same time, the present invention provides a method for regulating the surface wettability of an ultra-thin aluminum foil current collector and its application in lithium-ion batteries, especially in lithium-ion battery positive electrode current collectors.

[0008] In order to solve the above technical problems, the technical solution adopted by the present invention is: A method for regulating the surface wettability of an ultra-thin aluminum foil current collector, the preparation process of which is as follows: 1. Use alcohol to clean the aluminum foil and dry it; Second, a cleaned ultra-thin aluminum foil (9μm) is used as the anode, graphite, platinum sheet, stainless steel, or aluminum foil is used as the cathode, and an iron nitrate-based metal salt solution containing a complexing agent, surfactant, and preservative is used as the electrolyte. Electrochemical process parameters are applied to electrochemically treat the anode aluminum foil. At the same time, ultraviolet light is used as the radiation source, and the aluminum foil surface is treated with specific parameters during the etching process. 3. Wash and dry the treated aluminum foil with deionized water.

[0009] The concentration of the ferric nitrate solution in step 2 is 0.01-1 mol / L; the mild etching effect of nitrate is utilized to generate nanopores on the surface of the aluminum foil.

[0010] The complexing agent in step 2 is ammonium nitrate, sodium citrate, ethylenediaminetetraacetic acid or potassium sodium tartrate, with a concentration of 0.01~0.1mol / L; by complexing Fe 3+ 、Al 3+ etc., to prevent metal ion precipitation, ensure solution activity, and promote the redox reaction to proceed evenly on the surface of aluminum foil.

[0011] The surfactant in step 2 is sodium dodecyl sulfate, sodium dodecylbenzenesulfonate, or hexadecyltrimethylammonium bromide, with a concentration of 0.1-3 g / L. It reduces the surface tension of the aluminum foil, ensuring uniform etching, facilitating uniform pore formation, and reducing the accumulation of bubbles on the foil surface.

[0012] The preservative in step two is aniline or thiourea, with a concentration of 0.05-2%. This prevents uneven etching of the aluminum foil surface, preventing perforation. Furthermore, through the synergistic effects of electrochemistry and UV light, polar groups are introduced to the aluminum foil surface, forming a conductive network structure.

[0013] The electrochemical etching method in step 2 includes constant voltage, constant current, constant power, or cyclic voltammetry.

[0014] in: The parameters of the constant voltage mode are: voltage of 2.0~3.6 V, etching time of 1~9 min, and etching solution temperature of 25~75℃.

[0015] The parameters of the constant current mode are: current of 0.05~0.2 mA, etching time of 1~5 min, and etching solution temperature of 25~60℃.

[0016] The parameters of the constant power mode are: power of 1~5 W, etching time of 1~5 min, and solution temperature of 25~55 °C.

[0017] The cyclic voltammetry mode parameters are: scanning voltage range: -0.3~1.2V, speed 50mV / s, number of cycles 1~5, and solution temperature 25~40℃.

[0018] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 3~8mW / cm 2 The irradiation distance is 15~20cm, the irradiation angle is 60~90°, and N2 is passed during the process with a flow rate of 0.1~0.5L / min to avoid the formation of excessively thick oxides on the surface of the aluminum foil to hinder the etching process and enhance the bonding effect between the polar groups and the aluminum foil.

[0019] The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 8~15mW / cm 2 The irradiation distance is 20~30cm, the irradiation angle is 50~70°, O2 is passed during the process, and the flow rate is 0.5~1L / min. Under ultraviolet irradiation, active oxygen free radicals are generated, which participate in the aniline polymerization process and enhance the conductivity.

[0020] The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 3~5mW / cm 2 The irradiation distance is 25~30cm, the irradiation angle is 40~60°, and CO2 is passed during the process with a flow rate of 0.2~1L / min, providing mild acidic conditions, promoting the introduction of polar aniline groups, reducing excessive corrosion of aluminum foil, and optimizing interface bonding.

[0021] The invention discloses an ultra-thin aluminum foil current collector. The surface of the aluminum foil current collector has a uniform nanopore structure with a pore diameter of 10-30 nm. Polyaniline groups are introduced into the surface of the nanopore structure.

[0022] The invention discloses an application of an ultra-thin aluminum foil current collector in a lithium ion battery, especially in a positive electrode current collector of a lithium ion battery.

[0023] Compared with the prior art, the present invention has the following beneficial effects: (1) The present invention uses a mild, environmentally friendly iron nitrate-based solution as the electrolytic etching solution, which is pollution-free. The nanopore structure prepared on the ultra-thin aluminum foil has strong controllability, simple process and high production efficiency. The complexing agent used in the present invention can complex the Fe 3+ , preventing metal ion precipitation, ensuring solution activity, and promoting uniform redox reactions on the aluminum foil surface. The surfactant used can improve the wettability of the aluminum foil surface and the uniformity of the solution components, preventing agglomeration and accelerating the etching process. The antiseptic used can inhibit perforation caused by localized corrosion and improve etching uniformity and selectivity.

[0024] (2) During the electrochemical treatment, the aluminum foil surface is irradiated with ultraviolet light of specific parameters, which activates the surface and improves the etching rate and uniformity of the aluminum foil surface, avoiding pitting caused by uneven diffusion of nitrate ions and ensuring uniform nanopore size. In addition, under multi-stage ultraviolet light irradiation parameters, nitrate ions are in situ doped and embedded into the polyaniline molecular chains, improving the surface conductivity. At the same time, it promotes the formation of a conductive polyaniline film layer on the aluminum foil surface, reduces the corrosion of the electrolyte on the aluminum foil current collector, and improves the stability of the aluminum foil current collector during the battery cycle charge and discharge process.

[0025] (3) The introduction of polyaniline polar groups on the surface of ultra-thin aluminum foil synergistically forms a conductive network with the nanoporous structure. This can improve the surface conductivity of lithium iron phosphate materials with poor conductivity and reduce the amount of conductive agent used. The prepared nanoporous aluminum foil is applied to the positive electrode current collector of lithium-ion batteries, which can effectively improve its binding force with lithium iron phosphate and effectively inhibit the phenomenon of lithium iron phosphate volume expansion and shedding during the cycle, effectively improving the capacity and cycle life of lithium-ion batteries.

[0026] The present invention relates to a method for regulating the surface wettability of an ultra-thin aluminum foil current collector and its application, so as to solve the problems of smooth surface, easy shedding of lithium iron phosphate, easy perforation of the ultra-thin aluminum foil by conventional etching, low efficiency and high pollution of the ultra-thin aluminum foil current collector for high-energy-density lithium-ion batteries. The preparation method of the present invention is as follows: first, the aluminum foil is cleaned and dried; then, an environmentally friendly and mild iron nitrate-based metal salt solution containing a complexing agent, additives and preservatives is used as an electrolyte, and a simple and efficient electrochemical process is used. At the same time, multi-stage ultraviolet light irradiation is used as an auxiliary means to construct a uniform and morphologically controllable nanopore structure on the surface of the ultra-thin aluminum foil with a thickness of 9 μm. The pore size is 10-30 nm, providing binding sites for lithium iron phosphate particles to form an meshing effect; at the same time, chemical polar groups are introduced to further enhance the wettability between the positive electrode lithium iron phosphate and the aluminum current collector. The current collector forms a conductive network between the nanopores on the aluminum foil surface and the lithium iron phosphate layer through a nanoporous structure combined with surface-modified chemical polar groups, significantly reducing the amount of conductive agent in the electrode, delaying the corrosion of the electrolyte on the aluminum foil, and improving the specific capacity and cycle stability of the lithium-ion battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is the surface morphology of the ultra-thin aluminum foil treated by the method of Comparative Example 1; Figure 2 The contact angle of the ultra-thin aluminum foil surface treated by the method of Comparative Example 1; Figure 3 This is a surface morphology image of the ultra-thin aluminum foil treated by the method of Example 1 of the present invention; Figure 4 This is an infrared spectrum of the surface of the ultra-thin aluminum foil treated by the method of Example 1 of the present invention; Figure 5 The contact angle of the ultra-thin aluminum foil surface treated by the method of Example 1 of the present invention; Figure 6 The morphology of the ultra-thin aluminum foil treated by the method of Example 1 of the present invention after 200 cycles of charge and discharge; Figure 7 This is the surface morphology of the ultra-thin aluminum foil treated by the method of Comparative Example 2; Figure 8 The contact angle of the ultra-thin aluminum foil surface treated by the method of Comparative Example 2; Figure 9 This is the surface morphology of the ultra-thin aluminum foil treated by the method of Comparative Example 3; Figure 10 This is the surface morphology of the ultra-thin aluminum foil treated by the method of Comparative Example 4; Figure 11 The contact angle of the ultra-thin aluminum foil surface treated by the method of Comparative Example 4; Figure 12 This is the surface morphology of the ultra-thin aluminum foil treated by the method of Comparative Example 5; Figure 13This is the infrared spectrum of the surface of the ultra-thin aluminum foil treated by the method of Comparative Example 5; Figure 14 The contact angle of the ultra-thin aluminum foil surface treated by the method of Comparative Example 5; Figure 15 This is the morphology of the ultra-thin aluminum foil treated by the method of Comparative Example 5 after 200 cycles of charge and discharge. DETAILED DESCRIPTION

[0028] The present invention will be further described in detail below with reference to the accompanying drawings and specific examples. The following examples are only used to illustrate the present invention and are not intended to limit the scope of the present invention.

[0029] Comparative Example 1:

[0030] The ultra-thin aluminum foil current collector prepared in this comparative example.

[0031] A method for regulating the surface wettability of an ultra-thin aluminum foil current collector is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and graphite as the cathode. The concentration of ferric nitrate in the etching electrolyte is 0.01 mol / L, the chelating agent is sodium citrate with a concentration of 0.01 mol / L, the surfactant is sodium dodecyl sulfate with a concentration of 0.5 g / L, and the preservative is aniline with a concentration of 0.05wt%. The electrochemical etching parameters are constant voltage, etching voltage of 2.0 V, etching time of 9 min, and etching solution temperature of 25°C. The anode aluminum foil is electrochemically etched.

[0032] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into two stages: The first etching stage of 254nm UV irradiation lasted 4.5 minutes, and the light intensity on the aluminum foil surface was 3mW / cm 2 , irradiation distance 20cm, irradiation angle 60°, N2 flow during the process, flow rate 0.2L / min.

[0033] The second etching stage lasted 4.5 minutes, and the light intensity irradiating the aluminum foil surface was 10 mW / cm 2 , irradiation distance 30cm, irradiation angle 50°, O2 flow during the process, flow rate 0.5L / min.

[0034] 3. Wash and dry the treated aluminum foil with deionized water.

[0035] The surface morphology, wettability, and tensile strength were measured. The electrochemically etched aluminum foil prepared in this comparative example was used as the positive current collector, and a lithium iron phosphate electrode slurry was applied, in which the lithium iron phosphate weighed 0.2 g, the conductive carbon black was 0.021 g, and the adhesive PVDF was 0.025 g. The positive electrode sheet was prepared and cut, and the peel strength of the lithium iron phosphate active material was measured. The 2032 button battery was assembled in a glove box, and the battery discharge capacity was measured.

[0036] from Figure 1 It can be seen that the ultra-thin aluminum foil current collector prepared in this comparative example has been etched, but no uniform nanopores have been formed. The strength of the aluminum foil was tested according to GB / T 2884, and the tensile strength of the ultra-thin aluminum foil treated in this comparative example dropped to 216 MPa. Figure 2 It can be seen that its surface contact angle is 26.1°, which indicates good wettability and is conducive to the combination with active materials. The four-probe test shows that the surface resistance is 3.27 This is due to surface oxidation during the etching process, which increases surface resistance. A 180-degree peel test conducted according to GB / T2792-2014 showed that the bond strength between the ultra-thin aluminum foil prepared in this comparative example and the active material was 305.7 N·m. The battery assembled with this foil achieved a discharge capacity of 113 mAh / g. After 200 cycles of 1C charge and discharge, the discharge capacity dropped to 89.4 mAh / g. Example 1:

[0037] The present embodiment provides a method for controlling the wettability of an ultra-thin aluminum foil current collector surface. Specifically, the surface of the aluminum foil current collector has a uniform nanopore structure with a pore diameter of 10 to 30 nm; and polyaniline groups are introduced into the surface of the nanopore structure.

[0038] A method for regulating the surface wettability of an ultra-thin aluminum foil current collector is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and the aluminum foil as the cathode. The concentration of ferric nitrate in the etching electrolyte is 0.025 mol / L, the chelating agent is ammonium nitrate, the concentration is 0.05 mol / L, the surfactant is sodium dodecylbenzenesulfonate, the concentration is 1 g / L, the preservative is aniline, the concentration is 1wt%, the electrochemical etching parameters are, cyclic voltammetry mode, the parameters are: scanning voltage range: -0.3~1.2V, speed 50mV / s, number of cycles is 3, and the solution temperature is 25℃.

[0039] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage of UV irradiation accounts for 1 / 4 of the total etching time, and the light intensity irradiated on the aluminum foil surface is 8mW / cm 2The irradiation distance was 15 cm, the irradiation angle was 90°, and N2 was passed during the process with a flow rate of 0.3 L / min.

[0040] The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 12mW / cm 2 The irradiation distance was 20 cm, the irradiation angle was 70°, and O2 was passed during the process with a flow rate of 0.5 L / min.

[0041] The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 5mW / cm 2 The irradiation distance was 25 cm, the irradiation angle was 60°, and CO2 was passed during the process with a flow rate of 0.3 L / min.

[0042] This embodiment provides an application of an ultra-thin aluminum foil current collector in a lithium-ion battery.

[0043] 3. Wash and dry the treated aluminum foil with deionized water.

[0044] The surface morphology, wettability, and tensile strength were measured. The electrochemically etched aluminum foil prepared in this example was used as the positive current collector. A lithium iron phosphate electrode slurry was applied, wherein the lithium iron phosphate weighed 0.2 g, the conductive carbon black was 0.013 g, and the adhesive PVDF was 0.025 g. A positive electrode sheet was prepared and cut. The peel strength of the lithium iron phosphate active material was measured, and 2032 button batteries were assembled in a glove box, and the battery discharge capacity was measured.

[0045] from Figure 3 It can be seen that the surface of the ultra-thin aluminum foil current collector prepared in this embodiment has constructed a uniform nanopore structure with a pore size of 10-30 nm. Figure 4 The infrared spectrum of the aluminum foil surface treated by the method of this embodiment shows that at 3240.00 cm -1 The absorption peak at about 1560.00 cm-1 can be attributed to the stretching vibration of the NH bond of polyaniline. The stretching vibration of the quinone structure (N=Q=N) in polyaniline is about 1560.00 cm-1. -1 1476.46 cm -1 The absorption peak at 1298.89 cm is caused by the stretching vibration of C=C in the benzene structure of polyaniline. The stretching vibration of CN on the benzene ring structure of polyaniline is at about 1298.89 cm -1 800.31 cm -1 The absorption peak at can be attributed to the stretching vibration of =CH in polyaniline, indicating that the polyaniline group has been successfully introduced into the surface of the aluminum foil nanoporous structure. The tensile strength of the aluminum foil is 234 MPa, which is basically consistent with the mechanical properties of the aluminum foil before treatment. Figure 5 It can be seen that the surface contact angle is significantly reduced to 18.6°, and the wettability is improved, which is conducive to the combination with the active material. The surface resistance is 2.21 This is due to the nanoporous structure and polyaniline groups on the surface of the ultra-thin aluminum foil, which form a conductive network and reduce the amount of conductive agent to half of the original amount. From the peeling experiment, it can be seen that the bonding strength between the ultra-thin aluminum foil prepared in this embodiment and the active material is as high as 431.6 N·m. The assembled battery has an excellent discharge capacity of 165.8 mAh / g. After 200 cycles of 1C charge and discharge, its discharge capacity is still 148.6 mAh / g. The surface of the aluminum foil remains relatively intact, with no obvious signs of electrolyte corrosion. Figure 6 shown.

[0046] Comparative Example 2:

[0047] A method for regulating the surface wettability of an ultra-thin aluminum foil current collector in this comparative example is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and stainless steel as the cathode. The concentration of ferric nitrate in the etching electrolyte is 0.5 mol / L, the chelating agent is ethylenediaminetetraacetic acid, the concentration is 0.1 mol / L, the surfactant is hexadecyltrimethylammonium bromide, the concentration is 0.1 g / L, the preservative is thiourea, the concentration is 2wt%, and the electrochemical etching parameters are constant current mode, the parameters are: current is 0.2 mA, time is 5 min, and the solution temperature is 50°C.

[0048] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage of UV irradiation lasts for 1.25 minutes, and the light intensity on the aluminum foil surface is 10mW / cm 2 The irradiation distance was 16 cm, the irradiation angle was 90°, and N2 was passed during the process with a flow rate of 0.05 L / min.

[0049] The second etching stage lasted 2.5 minutes, and the light intensity irradiating the aluminum foil surface was 17 mW / cm 2 , irradiation distance 20cm, irradiation angle 70°, O2 flow during the process, flow rate 2L / min.

[0050] The third etching stage lasted 1.25 minutes, and the light intensity irradiating the aluminum foil surface was 8 mW / cm 2 The irradiation distance was 25 cm, the irradiation angle was 60°, and CO2 was passed during the process with a flow rate of 0.1 L / min.

[0051] 3. Wash and dry the treated aluminum foil with deionized water.

[0052] The surface morphology, wettability, and tensile strength were measured. The electrochemically etched aluminum foil prepared in this comparative example was used as the positive electrode current collector, and a lithium iron phosphate electrode slurry was applied, in which the lithium iron phosphate weighed 0.2 g, the conductive carbon black was 0.027 g, and the adhesive PVDF was 0.025 g. The positive electrode sheet was prepared and cut, and the peel strength of the lithium iron phosphate active material was measured. The 2032 button battery was assembled in a glove box, and the battery discharge capacity was measured.

[0053] from Figure 7 It can be seen that the nanopore structure on the surface of the ultra-thin aluminum foil current collector prepared in this comparative example collapses. The tensile strength of the aluminum foil is 209 MPa, which is basically consistent with the mechanical properties of the aluminum foil before treatment. Figure 8 It can be seen that the surface contact angle is significantly reduced to 21.4°, and the wettability is improved, which is conducive to the combination with the active material. The surface resistance is 3.07 , indicating that no conductive network has formed and the surface resistance has increased. The bonding strength between the ultra-thin aluminum foil prepared in this example and the active material is 362.9 N·m. The battery assembled with this foil has a discharge capacity of 124.2 mAh / g. After 200 cycles of 1C charge and discharge, the discharge capacity drops to 76.9 mAh / g.

[0054] Comparative Example 3:

[0055] A method for regulating the surface wettability of an ultra-thin aluminum foil current collector in this comparative example is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; Second, a cleaned ultra-thin aluminum foil was used as the anode and the aluminum foil as the cathode. The etching electrolyte contained 0.3 mol / L ferric nitrate, 0.08 mol / L potassium sodium tartrate as the complexing agent, and 2 g / L sodium dodecyl sulfate as the surfactant. The electrochemical etching parameters were constant power mode, 5 W power, 4 minutes, and a solution temperature of 50°C.

[0056] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage of UV irradiation takes up 1 / 4 of the total etching time, and the light intensity irradiated on the aluminum foil surface is 8mW / cm 2 The irradiation distance was 15 cm, the irradiation angle was 90°, and N2 was passed during the process with a flow rate of 0.5 L / min.

[0057] The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 15mW / cm 2 The irradiation distance was 20 cm, the irradiation angle was 70°, and O2 was passed during the process with a flow rate of 1 L / min.

[0058] The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 5mW / cm 2 The irradiation distance was 25 cm, the irradiation angle was 60°, and CO2 was passed during the process at a flow rate of 1 L / min.

[0059] 3. Wash and dry the treated aluminum foil with deionized water.

[0060] The surface morphology, wettability, and tensile strength were measured. The electrochemically etched aluminum foil prepared in this comparative example was used as the positive electrode current collector, and a lithium iron phosphate electrode slurry was applied, in which the lithium iron phosphate weighed 0.2 g, the conductive carbon black was 0.034 g, and the adhesive PVDF was 0.025 g. The positive electrode sheet was prepared and cut, and the peel strength of the lithium iron phosphate active material was measured. The 2032-type button battery was assembled in a glove box, and the battery discharge specific capacity was measured.

[0061] from Figure 9 It can be seen that due to the lack of preservative components, the aluminum foil surface is rapidly etched under the action of electrochemistry and light irradiation. The ultra-thin aluminum foil current collector prepared in this comparative example has a perforation phenomenon, the largest of which is tens of microns. The tensile strength of the aluminum foil drops sharply to 62MPa, and the ability to carry active materials is basically lost. The surface resistivity is 3.16 , the resistivity is relatively large. Since the ultra-thin aluminum foil has been perforated and damaged, effective data cannot be obtained from the peeling test and charge-discharge test.

[0062] Comparative Example 4:

[0063] This comparative example uses an untreated ultra-thin aluminum foil current collector with a thickness of 9 μm and is carried out according to the following steps: The aluminum foil was cleaned with alcohol and dried; the surface morphology, wettability, and tensile strength were measured. The electrochemically etched aluminum foil prepared in this example was used as the positive electrode current collector, and a lithium iron phosphate electrode slurry was applied, wherein the lithium iron phosphate weighed 0.2 g, the conductive carbon black weighed 0.025 g, and the adhesive PVDF weighed 0.025 g. A positive electrode sheet was prepared and cut. The peel strength of the lithium iron phosphate active material was measured, and 2032 button batteries were assembled in a glove box, and the battery discharge specific capacity was measured.

[0064] from Figure 10 It can be seen that there are obvious rolling marks on the surface of the unetched aluminum foil. The tensile strength of the ultra-thin aluminum foil is 237 MPa. Figure 11 It can be seen that its surface contact angle is relatively large, which is 80.4°. The surface resistance is 2.48 The peeling test showed that the bonding strength between the ultra-thin aluminum foil and the active material was 291.3 N·m. The 2032 button-type battery assembled with the foil had a discharge capacity of 113.4 mAh / g. After 200 cycles of 1C charge and discharge, the discharge capacity dropped to 61.8 mAh / g.

[0065] Comparative Example 5:

[0066] A method for regulating the surface wettability of an ultra-thin aluminum foil current collector in this comparative example is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and stainless steel as the cathode. The concentration of ferric nitrate in the etching electrolyte is 0.5 mol / L, the chelating agent is ammonium nitrate with a concentration of 0.5 mol / L, the surfactant is hexadecyltrimethylammonium bromide with a concentration of 2 g / L, the preservative is thiourea with a concentration of 1%, and the electrochemical etching parameters are cyclic voltammetry mode, with the following parameters: scanning voltage range: -0.3~1.2V, speed 50mV / s, number of cycles 3, and solution temperature 25℃.

[0067] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage of UV irradiation takes up 1 / 4 of the total etching time, and the light intensity irradiated on the aluminum foil surface is 3mW / cm 2 , irradiation distance 10cm, irradiation angle 50°, N2 flow during the process, flow rate 0.4L / min.

[0068] The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 10mW / cm 2 The irradiation distance was 15 cm, the irradiation angle was 80°, and O2 was passed during the process with a flow rate of 0.7 L / min.

[0069] The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 3mW / cm 2 The irradiation distance was 20 cm, the irradiation angle was 30°, and CO2 was passed during the process with a flow rate of 0.3 L / min.

[0070] 3. Wash and dry the treated aluminum foil with deionized water.

[0071] The surface morphology, wettability, and tensile strength were measured. The electrochemically etched aluminum foil prepared in this comparative example was used as the positive current collector, and a lithium iron phosphate electrode slurry was applied, in which the lithium iron phosphate weighed 0.2 g, the conductive carbon black was 0.023 g, and the adhesive PVDF was 0.025 g. The positive electrode sheet was prepared and cut, and the peel strength of the lithium iron phosphate active material was measured. The 2032 button battery was assembled in a glove box, and the battery discharge capacity was measured.

[0072] from Figure 12 It can be seen that the ultra-thin aluminum foil current collector prepared in this comparative example has been etched, but no uniform nanopores have been formed. Figure 13 Infrared spectrum shows that 3350cm -1NH stretching vibration, 1640 cm -1 、1506cm -1 、1415cm -1 is the NH bending vibration absorption peak, 856 cm -1 The peak is the out-of-plane deformation vibration absorption peak. This is because the ammonium groups in the solution components can be introduced into the aluminum foil surface under electrochemical and photoinitiation. However, since the conductive network structure is not formed as in Example 1, the amount of conductive carbon black is not effectively reduced, and the tensile strength of the treated ultra-thin aluminum foil drops to 211 MPa. Figure 14 It can be seen that the surface contact angle is significantly reduced to 23.6°, and the wettability is improved, which is conducive to the combination with the active material. The surface resistance is 3.03 This is because the surface oxidation during the etching process leads to an increase in surface resistance. The bonding strength between the ultra-thin aluminum foil prepared in this comparative example and the active material is 318.4 N·m. The discharge capacity of the assembled battery is 127.6 mAh / g. After 200 cycles of charge and discharge at 1C, the discharge capacity drops to 86.2 mAh / g. In addition, the surface of the aluminum foil reacts with the electrolyte during the charge and discharge process, and there are obvious corrosion marks on the surface, such as Figure 15 shown. Example 2:

[0073] The difference between this embodiment and embodiment 1 is that: A method for regulating the surface wettability of an ultra-thin aluminum foil current collector is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and graphite as the cathode. The concentration of ferric nitrate in the etching electrolyte is 0.01 mol / L, the chelating agent is sodium citrate with a concentration of 0.01 mol / L, the surfactant is sodium dodecyl sulfate with a concentration of 0.1 g / L, the preservative is thiourea with a concentration of 0.05 wt%. The electrochemical etching parameters are: cyclic voltammetry mode, the parameters are: scanning voltage range: -0.3~1.2 V, speed 50 mV / s, number of cycles 5, and solution temperature 40°C.

[0074] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage of UV irradiation accounts for 1 / 4 of the total etching time, and the light intensity irradiated on the aluminum foil surface is 3mW / cm 2 , irradiation distance 20cm, irradiation angle 60°, N2 was passed during the process, and the flow rate was 0.1L / min.

[0075] The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 8mW / cm 2, irradiation distance 30cm, irradiation angle 50°, O2 flow during the process, flow rate 1L / min.

[0076] The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 3mW / cm 2 The irradiation distance was 30 cm, the irradiation angle was 40°, and CO2 was passed during the process with a flow rate of 0.2 L / min. Example 3:

[0077] The difference between this embodiment and embodiment 1 is that: A method for regulating the surface wettability of an ultra-thin aluminum foil current collector is provided, which is carried out in the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and the platinum sheet as the cathode. The concentration of ferric nitrate in the etching electrolyte is 1 mol / L, the chelating agent is ethylenediaminetetraacetic acid, the concentration is 0.1 mol / L, the surfactant is hexadecyltrimethylammonium bromide, the concentration is 3 g / L, the preservative is aniline, the concentration is 2 wt%, the electrochemical etching parameters are, cyclic voltammetry mode, the parameters are: scanning voltage range: -0.3~1.2V, speed 50mV / s, number of turns is 1 turn, and the solution temperature is 30℃.

[0078] During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage of UV irradiation accounts for 1 / 4 of the total etching time, and the light intensity irradiated on the aluminum foil surface is 6mW / cm 2 The irradiation distance was 18 cm, the irradiation angle was 70°, and N2 was passed during the process with a flow rate of 0.5 L / min.

[0079] The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 15mW / cm 2 The irradiation distance was 25 cm, the irradiation angle was 60°, O2 was passed during the process, and the flow rate was 0.7 L / min.

[0080] The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 4mW / cm 2 The irradiation distance was 27 cm, the irradiation angle was 50°, and CO2 was passed during the process with a flow rate of 1 L / min. Example 4:

[0081] The difference between this embodiment and embodiment 1 is that: A method for regulating the surface wettability of an ultra-thin aluminum foil current collector is carried out according to the following steps: 1. Use alcohol to clean the aluminum foil and dry it; 2. Use the cleaned ultra-thin aluminum foil as the anode and stainless steel as the cathode. The concentration of ferric nitrate in the etching electrolyte is 0.02 mol / L, the chelating agent is potassium sodium tartrate, the concentration is 0.1 mol / L, the surfactant is sodium dodecylbenzenesulfonate, the concentration is 2 g / L, the preservative is aniline, the concentration is 1.5wt%. The electrochemical etching parameters are: constant voltage mode, voltage is 2.0 V, etching time is 5 min, and etching solution temperature is 25 °C.

[0082] The rest is the same as in Example 1. Example 5:

[0083] The only difference between this embodiment and embodiment 4 is that: in constant voltage mode, the voltage is 3.6 V, the etching time is 1 min, and the etching solution temperature is 75°C. Example 6:

[0084] The only difference between this embodiment and embodiment 4 is that: in constant voltage mode, the voltage is 3.0 V, the etching time is 9 minutes, and the etching solution temperature is 50°C. Example 7:

[0085] The only difference between this embodiment and embodiment 4 is that the constant current mode is used instead of the constant voltage mode. The parameters of the constant current mode are: current of 0.05 mA, time of 5 min, and solution temperature of 25°C. Example 8:

[0086] The only difference between this embodiment and embodiment 4 is that the constant current mode is used instead of the constant voltage mode. The parameters of the constant current mode are: current of 0.2 mA, time of 1 min, and solution temperature of 60°C. Example 9:

[0087] The only difference between this embodiment and embodiment 4 is that the constant power mode is used instead of the constant voltage mode. The parameters of the constant power mode are: power of 1 W, time of 5 min, and solution temperature of 25°C.

[0088] Example 10:

[0089] The only difference between this embodiment and embodiment 4 is that the constant voltage mode is replaced by the constant power mode, and the parameters of the constant power mode are: power of 5 W, time of 1 min, and solution temperature of 55°C.

[0090] The performance data of the examples of the present invention and the comparative examples are shown in Table 1 below.

[0091] Table 1 is the performance data of the ultra-thin aluminum foil processed by the embodiment and comparative example methods

[0092] It should be understood that in order to streamline the present disclosure and aid understanding of one or more of the various inventive aspects, in the above description of exemplary embodiments of the invention, various features of the invention are sometimes grouped together into a single embodiment, figure, or description thereof. However, this disclosed method should not be interpreted as reflecting an intention that the claimed invention requires more features than are expressly recited in each claim. Rather, as reflected in the claims, inventive aspects lie in less than all of the features of the previously disclosed embodiments. Accordingly, the claims that follow the detailed description are hereby expressly incorporated into this detailed description, with each claim standing on its own as a separate embodiment of the invention.

[0093] Although the present invention has been described with respect to a limited number of embodiments, it will be apparent to those skilled in the art, having benefit of the foregoing description, that other embodiments are contemplated within the scope of the invention thus described. Furthermore, it should be noted that the language used in this specification has been selected primarily for readability and didactic purposes, rather than for the purpose of explaining or limiting the subject matter of the present invention. Consequently, many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the appended claims. The disclosure of the present invention is intended to be illustrative rather than restrictive of the scope of the invention, which is defined by the appended claims.

[0094] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for regulating the surface wettability of an ultra-thin aluminum foil current collector, characterized in that: The following steps are involved:

1. Use alcohol to clean the aluminum foil and dry it; Second, a cleaned ultra-thin aluminum foil is used as the anode, graphite, platinum sheet, stainless steel or aluminum foil is used as the cathode, and a ferric nitrate-based metal salt solution containing a complexing agent, a surfactant and a preservative is used as the electrolyte. The concentration of the ferric nitrate solution is 0.01-1 mol / L. Electrochemical etching is performed to electrochemically treat the anode aluminum foil. At the same time, ultraviolet light is used as the radiation light source to treat the surface of the aluminum foil during the etching process. During the electrochemical treatment of aluminum foil, the UV wavelength is 254 nm and the irradiation is divided into three stages: The first etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 3~8mW / cm 2 , irradiation distance 15~20cm, irradiation angle 60~90°, N2 flow during the process, flow rate 0.1~0.5L / min; The second etching stage takes up half of the total etching time, and the light intensity irradiating the aluminum foil surface is 8~15mW / cm 2 , irradiation distance 20~30cm, irradiation angle 50~70°, O2 flow during the process, flow rate 0.5~1L / min; The third etching stage takes up 1 / 4 of the total etching time, and the light intensity irradiating the aluminum foil surface is 3~5mW / cm 2 , irradiation distance 25~30cm, irradiation angle 40~60°, CO2 flow during the process, flow rate 0.2~1L / min; 3. Wash and dry the treated aluminum foil with deionized water.

2. The control method according to claim 1, wherein In step 2, the complexing agent is ammonium nitrate, sodium citrate, ethylenediaminetetraacetic acid or potassium sodium tartrate, with a concentration of 0.01~0.1mol / L; the surfactant is sodium dodecyl sulfate, sodium dodecylbenzenesulfonate or hexadecyltrimethylammonium bromide, with a concentration of 0.1~3g / L; the preservative is aniline or thiourea, with a mass concentration of 0.05~2%.

3. The control method according to claim 1, characterized in that In step 2, the electrochemical etching method includes constant voltage, constant current, constant power, or cyclic voltammetry.

4. The control method according to claim 3, characterized in that The parameters of the constant voltage mode are: voltage of 2.0~3.6V, etching time of 1~9min, and etching solution temperature of 25~75℃.

5. The control method according to claim 3, characterized in that: The constant current mode parameters are: current 0.05~0.2mA, etching time 1~5min, and etching solution temperature 25~60℃.

6. The control method according to claim 3, characterized in that: The parameters of the constant power mode are: power of 1~5 W, etching time of 1~5 min, and solution temperature of 25~55 °C.

7. The control method according to claim 3, characterized in that: The cyclic voltammetry mode parameters are: scanning voltage range: -0.3~1.2V, speed 50mV / s, number of cycles 1~5, and solution temperature 25~40℃.

8. The ultra-thin aluminum foil current collector obtained by the control method according to any one of claims 1 to 7, characterized in that: The surface of the aluminum foil current collector has a uniform nanoporous structure with a pore diameter of 10~30nm; polyaniline groups are introduced into the surface of the nanoporous structure.

9. The ultra-thin aluminum foil current collector obtained by the control method according to claim 8, characterized in that: The thickness of the ultra-thin aluminum foil current collector is 9 μm.

10. Use of the ultra-thin aluminum foil current collector according to claim 8 in a lithium ion battery.

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