Preparation method of high-strength low-resistance functional aluminum current collector

Abstract

The invention discloses a preparation method of a high-strength low-resistance functional aluminum current collector, and relates to the technical field of lithium battery manufacturing. The preparation method of the functional aluminum current collector comprises the following steps: adding water into a binder for dispersion, adding aluminum powder and a dispersing agent for high-pressure homogeneous dispersion, adding conductive carbon black and graphite step by step, stirring to obtain carbon-coated slurry, coating the carbon-coated slurry on a tab blank area of the current collector and a welding surface, in contact with the current collector, of an adapter foil, and carrying out vacuum drying to obtain the functional aluminum current collector. And finally, the functional aluminum current collector is prepared through ultrasonic welding. The functional aluminum current collector prepared by the invention has the characteristics of high strength and low resistance, solves the problems of high resistance and low welding strength of the traditional functional aluminum current collector, and is suitable for manufacturing high-performance lithium batteries.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of lithium battery manufacturing, in particular to a preparation method of a high-strength low-resistance functional aluminum current collector. BACKGROUND

[0002] In the field of battery technology, the performance of the current collector is crucial to the overall performance of the battery. Traditional aluminum foil current collectors have a large mass, which restricts the improvement of the energy density of the battery, and the combination strength with the electrode active material is insufficient, which easily leads to poor interface contact and increased internal resistance in the cycle, affecting the charge and discharge efficiency and the service life.

[0003] Composite current collectors have been widely concerned in the lithium battery industry because they can improve the energy density and safety of the battery. The "sandwich" structure of "polymer thin film + metal conductive layer" needs to be connected by welding to realize conduction, but the existing technology has defects: in terms of conductivity, the film plating efficiency of processes such as vacuum evaporation plating and magnetron sputtering is low, the quality of the metal conductive layer is poor, the resistivity of the composite current collector is high, and it is difficult to meet the demand for high-power output; in terms of strength, the bonding force between the polymer thin film and the metal conductive layer is limited, and when subjected to external force or stress caused by volume change of the electrode material, the metal layer is easy to fall off and crack, resulting in damage to the structure of the current collector and an increase in resistance.

[0004] Therefore, it is a key problem to be solved in the field of batteries to develop a functional aluminum current collector with high strength and low resistance and an efficient preparation method, which is of great significance to promote the performance improvement of batteries and meet the needs of related fields. SUMMARY

[0005] The purpose of the present application is to provide a preparation method of a high-strength low-resistance functional aluminum current collector to solve the problems existing in the prior art.

[0006] To achieve the above-mentioned purpose, the present application provides the following technical scheme: A preparation method of a high-strength low-resistance functional aluminum current collector, comprising the following steps: S1: carbon paste preparation: add a binder to water, disperse, then add aluminum powder and a dispersing agent, perform high-pressure homogenization dispersion, then add conductive carbon black and graphite step by step, and stir to obtain a carbon paste; S2: coating of the carbon paste: coat the carbon paste on the tab blank area of the current collector and on the welding surface of the adapter foil in contact with the current collector to form a carbon coating layer, and then prepare a functional aluminum current collector by ultrasonic welding.

[0007] Further, the carbon paste comprises the following components: conductive carbon black, graphite, aluminum powder, a binder (PAA), and water, and the mass ratio is (1.5-2):1:0.5:7:35 in sequence; The solid content of the carbon paste is 8-10%, and the viscosity is 150-160 mPa·s.

[0008] Further, in step S1, the process conditions for dispersing the binder are: rotation speed 800-1000 rpm, time 30-45 min; The process conditions for high-pressure homogenization are: homogenization pressure 30000-32000 psi, rotation speed 300-400 rpm; The process conditions for stirring are: rotation speed 800-1200 rpm, time 30-45 min.

[0009] Further, in step S2, the coating thickness of the carbon-coated slurry is 1-2 µm; The welding process is: a 150 mm wide composite aluminum material is coated with the carbon-coated slurry, and the coating range is 140 mm, after which it enters the welding link; during welding, an unequal width welding method is used, and an aluminum foil with a thickness of 13 µm is selected, the carbon-coated slurry is first coated on a 200 mm wide foil, after the coating is completed, it is cut into the required narrow and wide foils, among which the narrow foil is 7 mm wide and the wide foil is 20 mm wide, and then ultrasonic welding is carried out; the ultrasonic welding parameters are: welding pressure 0.3-0.5 MPa, amplitude 60-65%, welding speed 5-6 m / min.

[0010] In the above technical solution, the adapter foil used for welding is also a carbon-coated foil, but only the welding surface in contact with the current collector needs to be coated with carbon, because the carbon-coated surface is rougher, when two carbon-coated surfaces come into contact, it can effectively prevent the size error caused by foil welding slip; during the welding process, the carbon-coated layer can absorb the welding head pressure, reduce the welding perforation, and the carbon-coated layer can effectively reduce the overcurrent resistance of the welding area.

[0011] In the above technical solution, to prevent the welding strength from being reduced, the coating area adopts a mesh design, which ensures the welding strength by retaining multiple metal layer direct contact points; to avoid the situation that the welding strength is low or even false welding due to the complete correspondence between the tab blank area and the mesh structure coating of the adapter foil, the mesh structures of the two are designed to be distributed in a staggered manner; by doping aluminum powder in the carbon-coated slurry and coating it on the welding area, additional metal particles are provided during the welding process, which promotes the bonding of the welding interface and improves the welding strength of the carbon-coated layer and the aluminum foil.

[0012] Further, the conductive carbon black in the carbon-coated slurry is surface modified, and the surface modification process is: Step one: material pretreatment: The conductive carbon black is treated at 280-290°C for 1-2 h under nitrogen protection to obtain pretreated conductive carbon black; silane-PEG is dissolved in 95% ethanol, and a silane-PEG solution is obtained after oxygen removal by nitrogen; Step two: grafting reaction: The pretreated conductive carbon black is put into a high-speed kneader, and the temperature is raised to 90-100 DEG C, the silane-PEG solution is added through an atomizing nozzle, the reaction is carried out at a rotating speed of 600-800 rpm for 15-20 min, then the temperature is lowered to 80 DEG C, the citric acid is added, stirring is carried out at a rotating speed of 400-500 rpm for 25-35 min, then nitrogen blowing is carried out for 10-15 min, and then the temperature is lowered to room temperature at a rate of 10 DEG C / min, to obtain the modified conductive carbon black.

[0013] Further, in step one, the silane-PEG solution comprises the following components: 5-10 wt% silane-PEG, and the balance is 95% ethanol.

[0014] Further, in step two, the atomizing nozzle parameters are: atomizing particle size 50-80 µm, and spraying pressure 0.3-0.5 MPa. The amount of the silane-PEG solution is 40-80 wt% of the mass of the pretreated conductive carbon black. The amount of the citric acid is 0.4-0.6 wt% of the mass of the pretreated conductive carbon black. The nitrogen blowing parameters are: nitrogen flow rate 2-3 L / min, and blowing pressure 0.1-0.2 MPa.

[0015] In the above technical solution, the silanol groups (-Si-OH) in the silane-PEG molecules are hydrolyzed into silanol groups (-Si-OH) in 95% ethanol solvent to form active intermediates; the surface of the pretreated conductive carbon black is rich in hydroxyl groups (-OH), and the silanol groups undergo a dehydration condensation reaction to form Si-O-C covalent bonds, so that the silane-PEG is chemically grafted on the surface of the carbon black; under the catalysis of citric acid, the unreacted silanol groups further condense to form Si-O-Si crosslinking structures, so as to enhance the stability of the grafted layer, and at the same time, the PEG segments (-O-CH2-CH2-) are connected to the surface of the conductive carbon black through covalent bonds, so as to impart hydrophilicity and steric hindrance effect to the conductive carbon black.

[0016] Compared with the prior art, the present application has the following beneficial effects: 1. The preparation method of the high-strength low-resistance functional aluminum current collector of the present application can absorb the pressure of the welding head through the carbon coating layer, reduce the light transmittance, reduce the overcurrent resistance, and at the same time ensure the welding strength.

[0017] 2. The preparation method of the high-strength low-resistance functional aluminum current collector of the present application can retain the metal contact points through the network coating and staggered structure design of the carbon slurry, combine with aluminum powder doping, improve the welding strength, reduce the virtual welding and perforation, and the welding strength is improved by 15%-20% compared with the traditional process.

[0018] 3. The preparation method of the high-strength low-resistance functional aluminum current collector, by coating a carbon coating layer in the welding area, the light transmittance and the overcurrent resistance are reduced, and the single-sided carbon coating of the welding foil is also carried out to increase the friction between the foils and avoid slipping.

[0019] 4. The preparation method of the high-strength low-resistance functional aluminum current collector, the conductive carbon black in the carbon coating slurry is replaced by modified conductive carbon black, the modified conductive carbon black retains the high conductivity of the original carbon black, and the steric hindrance of the PEG segment can effectively inhibit the agglomeration of the carbon black, and the "carbon black-graphite-aluminum powder" three-dimensional conductive network is formed with the aluminum powder, so that the volume resistivity of the carbon coating layer is reduced by 15%-20%, and the problem of high overcurrent resistance of the traditional carbon coating layer is solved. BRIEF DESCRIPTION OF DRAWINGS

[0020] Figure 1 It is a schematic diagram of the functional aluminum current collector welding structure of the present application. Figure 2 It is a schematic diagram of the carbon coating slurry coating of the functional aluminum current collector of the present application. In the figure: 1 is an active material; 2 is a tab blank area; 3 is a narrow foil; 4 is a welding area of a switching foil; 5 is a wide foil. DETAILED DESCRIPTION

[0021] The technical solutions in the embodiments of the present application will be described clearly and completely below in combination with the drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor fall within the scope of protection of the present application.

[0022] In the following specific embodiments: The binder is polyacrylic acid (PAA) with a viscosity of 61000 mPa·s; The dispersing agent is XY-140; The conductive carbon black has a particle size of 50 nm and an ash content of 0.1%; The graphite is graphite powder with a particle size of 1 µm; The aluminum powder has a particle size of 2 µm and a purity of 99.8%; The silane-PEG has a molecular weight of 5000 Da.

[0023] Embodiment 1: A preparation method of a high-strength low-resistance functional aluminum current collector, comprising the following steps: S1: Carbon coating slurry preparation: Add the binder to the water, disperse for 30 min at a speed of 800 rpm, then add the aluminum powder and dispersant, and perform high-pressure homogenization dispersion at a homogenization pressure of 30000 psi and a speed of 300 rpm for 30 min. Then add the conductive carbon black and graphite in stages, stir for 30 min at a speed of 800 rpm, and obtain the carbon coating slurry. The carbon coating slurry includes the following components: conductive carbon black, graphite, aluminum powder, binder (PAA), and water, with a mass ratio of 1.5:1:0.5:7:35. The solid content of the carbon coating slurry is 8%, and the viscosity is 150 mPa·s. S2: Coating of the carbon coating slurry: The carbon coating slurry is coated on the tab blank area 2 of the current collector and on the welding surface 4 of the adapter foil in contact with the current collector to form a carbon coating layer, and then a functional aluminum current collector is prepared through ultrasonic welding. The coating thickness of the carbon coating slurry is 1 µm. The welding process is as follows: a 150 mm wide composite aluminum material is selected to coat the carbon coating slurry, and the coating range is 140 mm. After completion, the welding link is entered. During welding, an unequal width welding method is adopted, and an aluminum foil with a thickness of 13 µm is selected. The carbon coating slurry is first coated on a 200 mm wide foil, and after the coating is completed, it is cut into the required narrow and wide foils. The narrow foil 3 is 7 mm wide, and the wide foil 5 is 20 mm wide. Subsequently, ultrasonic welding is performed. The ultrasonic welding parameters are as follows: welding pressure 0.3 MPa, amplitude 60%, and welding speed 5 m / min.

[0024] Example 2: A method for preparing a high-strength low-resistance functional aluminum current collector, comprising the following steps: S1: Carbon coating slurry preparation: Add the binder to the water, disperse for 30 min at a speed of 900 rpm, then add the aluminum powder and dispersant, and perform high-pressure homogenization dispersion at a homogenization pressure of 30000 psi and a speed of 300 rpm for 30 min. Then add the conductive carbon black and graphite in stages, stir for 30 min at a speed of 900 rpm, and obtain the carbon coating slurry. The carbon coating slurry includes the following components: conductive carbon black, graphite, aluminum powder, binder (PAA), and water, with a mass ratio of 1.5:1:0.5:7:35. The solid content of the carbon coating slurry is 8%, and the viscosity is 150 mPa·s. S2: Coating of the carbon coating slurry: The carbon coating slurry is coated on the tab blank area 2 of the current collector and on the welding surface 4 of the adapter foil in contact with the current collector to form a carbon coating layer, and then a functional aluminum current collector is prepared through ultrasonic welding. The coating thickness of the carbon coating slurry is 1 µm. The welding process is as follows: a 150mm wide composite aluminum material is selected and coated with carbon slurry over a coating range of 140mm, and then the welding process is started; an unequal width welding method is adopted during welding, and an aluminum foil with a thickness of 13µm is selected. The 200mm wide foil is first coated with carbon slurry, and after coating, it is cut into the required narrow and wide foils, where the narrow foil 3 is 7mm wide and the wide foil 5 is 20mm wide, and then ultrasonic welding is performed; the ultrasonic welding parameters are: welding pressure 0.3MPa, amplitude 60%, and welding speed 5m / min.

[0025] Example 3: A method for preparing a high-strength, low-resistance functional aluminum current collector, comprising the following steps: S1: Preparation of carbon coating slurry: Add the binder to water and disperse at 800 rpm for 30 minutes. Then, add aluminum powder and dispersant and disperse under high pressure homogenization at a homogenization pressure of 30,000 psi and a speed of 300 rpm for 30 minutes. Then, add modified conductive carbon black and graphite in steps and stir at 800 rpm for 30 minutes to obtain carbon coating slurry. The carbon coating slurry comprises the following components: modified conductive carbon black, graphite, aluminum powder, binder (PAA), and water in a mass ratio of 1.5:1:0.5:7:35. The solid content of the carbon coating slurry is 8%, and the viscosity is 150 mPa·s. S2: Coating of carbon coating slurry: Coating the carbon coating slurry on the blank area 2 of the tab of the current collector and on the welding surface 4 where the transfer foil contacts the current collector to form a carbon coating layer, and then ultrasonic welding is performed to prepare a functional aluminum current collector; The coating thickness of the carbon coating slurry is 1µm; The welding process is as follows: a 150mm wide composite aluminum material is selected and coated with carbon slurry over a coating range of 140mm, and then the welding process is started; an unequal width welding method is adopted during welding, and an aluminum foil with a thickness of 13µm is selected. The 200mm wide foil is first coated with carbon slurry, and after coating, it is cut into the required narrow and wide foils, where the narrow foil 3 is 7mm wide and the wide foil 5 is 20mm wide, and then ultrasonic welding is performed; the ultrasonic welding parameters are: welding pressure 0.3MPa, amplitude 60%, and welding speed 5m / min.

[0026] Modified conductive carbon black is produced by the following process: Step 1: Material pretreatment: Conductive carbon black was treated at 285° C. for 1.5 h under nitrogen protection to obtain pretreated conductive carbon black; silane-PEG was dissolved in 95% ethanol and deoxygenated by nitrogen to obtain a silane-PEG solution; the silane-PEG solution comprised the following components: 8 wt% silane-PEG and the balance 95% ethanol, by mass percentage; Step 2: Grafting reaction: The pretreated conductive carbon black was put into a high-speed kneader, heated to 95℃, and the silane-PEG solution was added through an atomizing nozzle. The reaction was carried out at a speed of 600 rpm for 20 min. Then, the temperature was lowered to 80℃, and the citric acid was added. The stirring was carried out at a speed of 500 rpm for 30 min. Subsequently, nitrogen was blown for 15 min. Then, the temperature was lowered to room temperature at a rate of 10℃ / min to obtain the modified conductive carbon black. The atomizing nozzle parameters were: atomizing particle size 50µm, spraying pressure 0.3MPa. The amount of the silane-PEG solution was 60wt% of the mass of the pretreated conductive carbon black. The amount of the citric acid was 0.4wt% of the mass of the pretreated conductive carbon black. The nitrogen blowing parameters were: nitrogen flow rate 2L / min, blowing pressure 0.1MPa.

[0027] Example 4: A preparation method of a high-strength low-resistance functional aluminum current collector, comprising the following steps: S1: Carbon paste preparation: The binder was added to water, and dispersed at a speed of 800 rpm for 30 min. Then, the aluminum powder and dispersant were added, and high-pressure homogenization dispersion was carried out. The dispersion was carried out at a homogenization pressure of 30000 psi and a speed of 300 rpm for 30 min. Then, the modified conductive carbon black and graphite were added step by step, and stirred at a speed of 800 rpm for 30 min to obtain the carbon coating paste. The carbon coating paste included the following components: modified conductive carbon black, graphite, aluminum powder, binder (PAA) and water, and the mass ratio was 1.5:1:0.5:7:35 in turn. The solid content of the carbon coating paste was 8%, and the viscosity was 150mPa·s. S2: Coating of the carbon coating paste: The carbon coating paste was coated on the tab blank area 2 of the current collector and on the welding surface 4 of the adapter foil in contact with the current collector to form a carbon coating layer. Then, the functional aluminum current collector was prepared by ultrasonic welding. The coating thickness of the carbon coating paste was 1µm. The welding process was as follows: a 150mm wide composite aluminum material was selected to coat the carbon coating paste, and the coating range was 140mm. After completion, the welding link was entered. During welding, the unequal width welding method was adopted, and an aluminum foil with a thickness of 13µm was selected. The carbon coating paste was coated on a 200mm wide foil, and after the coating was completed, it was cut into the required narrow and wide foils. The width of the narrow foil 3 was 7mm, and the width of the wide foil 4 was 20mm. Subsequently, ultrasonic welding was carried out. The ultrasonic welding parameters were: welding pressure 0.3MPa, amplitude 60%, and welding speed 5m / min.

[0028] The modified conductive carbon black was prepared by the following process: Step one: material pretreatment: The conductive carbon black was pretreated under nitrogen protection at 280°C for 2h to obtain pretreated conductive carbon black; the silane-PEG was dissolved in 95% ethanol, and the silane-PEG solution was obtained after oxygen removal by nitrogen; the silane-PEG solution comprises the following components: 5wt% silane-PEG, and the balance is 95% ethanol; Step two: grafting reaction: The pretreated conductive carbon black was put into a high-speed kneader, heated to 100°C, and the silane-PEG solution was added through an atomizing nozzle, and the reaction was carried out at a speed of 800rpm for 15min; then the temperature was lowered to 80°C, and citric acid was added, and stirred at a speed of 400rpm for 35min, and then nitrogen was blown for 10min, and then the temperature was lowered to room temperature at a rate of 10°C / min to obtain modified conductive carbon black.

[0029] The atomizing nozzle parameters are: atomizing particle size 50µm, spraying pressure 0.3MPa; The amount of silane-PEG solution is 40wt% of the mass of pretreated conductive carbon black; The amount of citric acid is 0.4wt% of the mass of pretreated conductive carbon black; The nitrogen blowing parameters are: nitrogen flow 2L / min, blowing pressure 0.1MPa.

[0030] Comparative Example 1: based on Example 1, adjust the carbon coating slurry formula, do not add aluminum powder, comprising the following steps: S1: carbon coating slurry preparation: add binder to water, disperse at a speed of 800rpm for 30min, then add aluminum powder, dispersant, and high-pressure homogenization dispersion, disperse at a homogenization pressure of 30000psi and a speed of 300rpm for 30min, then add modified conductive carbon black and graphite step by step, stir at a speed of 800rpm for 30min to obtain carbon coating slurry; the carbon coating slurry comprises the following components: modified conductive carbon black, graphite, binder (PAA) and water, and the mass ratio is 1.5:1:7:35; the solid content of the carbon coating slurry is 8%, and the viscosity is 150mPa·s; S2: coating of carbon coating slurry: the carbon coating slurry is coated on the tab blank area 2 of the current collector and the welding surface 4 in contact with the current collector of the adapter foil to form a carbon coating layer, and then a functional aluminum current collector is prepared by ultrasonic welding; The coating thickness of the carbon coating slurry is 1µm; The welding process is as follows: a 150 mm wide composite aluminum material is coated with the carbon coating slurry, and the coating range is 140 mm. After completion, it enters the welding link. During welding, the unequal width welding method is adopted, and an aluminum foil with a thickness of 13 pm is selected. The 200 mm wide foil is coated with the carbon coating slurry, and after the coating is completed, it is cut into the required narrow and wide two foils. The narrow foil 3 is 7 mm wide, and the wide foil 5 is 20 mm wide. Then ultrasonic welding is carried out. The ultrasonic welding parameters are as follows: welding pressure 0.3 MPa, amplitude 60%, and welding speed 5 m / min.

[0031] Comparative Example 2: Based on Example 3, the modified conductive carbon black preparation process is adjusted, including the following steps: S1: Carbon coating slurry preparation: add binder to water, disperse at a speed of 800 rpm for 30 min, then add aluminum powder and dispersant, and perform high-pressure homogenization dispersion at a homogenization pressure of 30000 psi and a speed of 300 rpm for 30 min. Then add the modified conductive carbon black and graphite step by step, stir at a speed of 800 rpm for 30 min, and obtain the carbon coating slurry. The carbon coating slurry includes the following components: modified conductive carbon black, graphite, aluminum powder, binder (PAA), and water, with a mass ratio of 1.5:1:0.5:7:35. The solid content of the carbon coating slurry is 8%, and the viscosity is 150 mPa·s. S2: Carbon coating slurry coating: coat the carbon coating slurry on the tab blank area 2 of the current collector and on the welding surface 4 of the adapter foil in contact with the current collector to form a carbon coating layer, and then prepare a functional aluminum current collector by ultrasonic welding. The coating thickness of the carbon coating slurry is 1 pm. The welding process is as follows: a 150 mm wide composite aluminum material is coated with the carbon coating slurry, and the coating range is 140 mm. After completion, it enters the welding link. During welding, the unequal width welding method is adopted, and an aluminum foil with a thickness of 13 pm is selected. The 200 mm wide foil is coated with the carbon coating slurry, and after the coating is completed, it is cut into the required narrow and wide two foils. The narrow foil 3 is 7 mm wide, and the wide foil 5 is 20 mm wide. Then ultrasonic welding is carried out. The ultrasonic welding parameters are as follows: welding pressure 0.3 MPa, amplitude 60%, and welding speed 5 m / min.

[0032] The modified conductive carbon black is prepared by the following process: placing the conductive carbon black in a high-temperature heat treatment electric furnace; first heating to 1300℃ under a nitrogen atmosphere, holding for 1 h; then heating to 1400℃, holding for 1 h; then heating to 1500℃, holding for 1 h, stopping heating, and naturally cooling to room temperature to obtain high-temperature calcined conductive carbon black; and ball milling the high-temperature calcined conductive carbon black to 300 mesh to obtain the modified conductive carbon black.

[0033] Experiment: take the functional aluminum current collector prepared from examples 1-4 and comparative examples 1-2, prepare samples, and test the performance of the samples, and the test results are shown in table 1: Welding strength test method: a sample with a width of 30 mm is prepared, and a tensile testing machine is used for testing at a test speed of 20 mm / min. During testing, the sample is installed in the clamps of the tensile testing machine, ensuring that the foils on both sides of the current collector are parallel to the clamps. One clamp holds the structure on one side of the current collector, and the other clamp holds the foil on the other side of the current collector. The tensile force direction of the two clamps is opposite, and the tensile force value when the welded part fails (such as wire breakage, welded interface separation, foil separation from the current collector, etc.) is recorded. This value is the welding strength; Welding area overcurrent resistance test method: a sample with a width of 30 mm is prepared, and a micro-resistance meter is used for testing. The probe clamps the two sides of the welding area, one side being a single-layer current collector and the other side being a double-layer foil.

[0034]

[0035] Conclusion: comparing the performance test data of the samples of comparative examples 1-4 and comparative examples 1-2, it is found that the functional aluminum current collector prepared by examples 1-4 has better welding strength and overcurrent resistance performance than the functional aluminum current collector prepared by comparative examples 1-2; Examples 3-4 use modified conductive carbon black, and both the welding strength and the overcurrent resistance performance are better than examples 1-2 using ordinary conductive carbon black, indicating that the conductive carbon black modified by silane-PEG grafting can further improve the welding strength and reduce the resistance by inhibiting agglomeration and constructing a three-dimensional conductive network; Comparative example 1 is based on example 1, and the carbon coating slurry formula is adjusted without adding aluminum powder. The functional aluminum current collector prepared has worse welding strength and overcurrent resistance performance than example 1, indicating that the addition of aluminum powder in the carbon coating slurry can effectively promote the bonding of the welding interface, improve the welding strength, and optimize the conductive path to reduce the resistance; Comparative example 2 is based on example 3, and the preparation process of the modified conductive carbon black is adjusted. The modified conductive carbon black is prepared by high-temperature calcination. The functional aluminum current collector prepared has worse welding strength and overcurrent resistance performance than example 3, indicating that the high-temperature calcination process can damage the microstructure integrity of the conductive carbon black, while the chemical grafting modification can better balance the conductivity and interface bonding performance; In summary, the present application optimizes the carbon coating slurry formula, designs the coating structure, and adjusts the process parameters, thereby simultaneously improving the welding strength and conductive performance of the functional aluminum current collector, which has significant advantages over the traditional process.

[0036] It will be apparent to those skilled in the art that the application is not limited to the details of the above-exemplified embodiments and that the present application can be implemented in other particular forms without departing from the spirit or essential characteristics of the present application. The embodiments should therefore be considered in all respects as illustrative and not restrictive, the scope of the application being indicated by the appended claims rather than by the above description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein. No reference signs in the claims should be considered as limiting the scope of the claims with respect to the figures of the patent document.

Claims

1. A method for preparing a high-strength, low-resistance functional aluminum current collector, characterized by: The following steps are involved: S1: Preparation of carbon coating slurry: Add the binder to water and disperse it, then add aluminum powder and dispersant, perform high pressure homogenization and dispersion, then add conductive carbon black and graphite step by step and stir to obtain carbon coating slurry; S2: Coating of carbon coating slurry: Coating the carbon coating slurry on the blank area (2) of the tab of the current collector and on the welding surface (4) where the transition foil contacts the current collector to form a carbon coating layer, and then ultrasonic welding is performed to prepare a functional aluminum current collector.

2. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 1, characterized in that: The carbon coating slurry includes the following components: conductive carbon black, graphite, aluminum powder, binder and water, with the mass ratio being (1.5-2):1:0.5:7:

35.

3. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 2, characterized in that: The carbon coating slurry has a solid content of 8-10% and a viscosity of 150-160 mPa·s.

4. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 1, characterized in that: The carbon coating layer is in a mesh shape.

5. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 1, characterized in that: The process conditions of the high-pressure homogenization are: homogenization pressure 30000-32000psi, rotation speed 300-400rpm.

6. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 1, characterized in that: The coating thickness of the carbon coating slurry is 1-2 μm.

7. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 1, characterized in that: The welding process is as follows: a 150 mm wide composite aluminum is coated with carbon slurry, and the coating range is 140 mm. After completion, the welding process is started; an unequal width welding method is adopted during welding, and an aluminum foil with a thickness of 13 μm is selected. The 200 mm wide foil is first coated with carbon slurry. After the coating is completed, the foil is cut into the required narrow and wide foils, wherein the narrow foil (3) has a width of 7 mm and the wide foil (5) has a width of 20 mm, and then ultrasonic welding is performed.

8. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 7, characterized in that: The ultrasonic welding parameters are: welding pressure 0.3-0.5 MPa, amplitude 60-65%, and welding speed 5-6 m / min.

9. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 2, characterized in that: The conductive carbon black in the carbon coating slurry is surface modified.

10. The method for preparing a high-strength, low-resistance functional aluminum current collector according to claim 9, characterized in that: The surface modification process is: Step 1: Material pretreatment: Conductive carbon black is treated under nitrogen protection at 280-290° C. for 1-2 hours to obtain pretreated conductive carbon black; silane-PEG is dissolved in 95% ethanol and deoxygenated by nitrogen to obtain a silane-PEG solution; Step 2: Grafting reaction: Pretreated conductive carbon black was placed in a high-speed kneader, the temperature was raised to 90-100°C, and a silane-PEG solution was added through an atomizing nozzle. The mixture was reacted at a speed of 600-800 rpm for 15-20 minutes. The temperature was then lowered to 80°C, citric acid was added, and the mixture was stirred at a speed of 400-500 rpm for 25-35 minutes. After that, nitrogen was purged for 10-15 minutes, and the mixture was cooled to room temperature at a rate of 10°C / min to obtain modified conductive carbon black.

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