Method for preparing functional current collector from polymer at low temperature

Abstract

The invention discloses a method for preparing a functional current collector from a polymer at low temperature, and relates to the technical field of current collectors. The method specifically comprises the following steps: S1, cleaning the surface of a base membrane to obtain a pretreated base membrane; s2, uniformly mixing the monomer solution, the functional substance solution and the free radical initiator solution to obtain a mixed solution; s3, coating the surface of the pretreated base film with the mixed solution, performing plasma low-temperature irradiation, standing at room temperature, washing and drying to form a polymer layer, thereby obtaining a current collector base film; s4, depositing a metal layer on the surface of the polymer layer of the current collector base film to obtain a functional current collector; according to the invention, the monomers with specific functional groups and a plurality of functional substances are introduced, the concentration and the ratio of the monomers and the functional substances are accurately controlled, and the technological process is further optimized, so that the comprehensive performance of the functional current collector is improved; the preparation method is simple to operate and easy to control, and has a good application prospect.

Description

Technical Field

[0001] The present invention relates to the technical field of current collectors, and specifically to a method for preparing a functional current collector at low temperature using a polymer. Background Art

[0002] A current collector is an important component in a battery, which is used to collect and conduct the current generated by the electrode material in the battery to an external circuit. Traditional current collector materials generally choose aluminum foil and copper foil, which have good electrical conductivity. However, traditional metal current collector materials have a relatively large density, and it is difficult to further reduce the thickness. It is difficult to improve the energy density of the battery. Moreover, when the battery thermal runaway or breakage causes a short circuit, it cannot cut off the power automatically, which is extremely likely to cause a fire and reduce the safety.

[0003] Therefore, in the prior art, a functional current collector is used as a new type of battery material, which has a "sandwich" structure, that is, the middle is a polymer polymer layer, and the outer layer is a metal conductive layer. Compared with traditional current collectors, the advantage is that part of the metal material is replaced by a polymer film material, which can effectively save costs, reduce the mass of the current collector, improve the energy density, and can play a buffering effect during short circuits and failures. A large amount of heat generated can melt the polymer layer to achieve a power-off effect and increase safety. However, due to the relatively thin metal layer of the functional current collector, the electrical conductivity is poor, and the interface between the polymer polymer layer and the metal foil is weak, which is prone to delamination during processing or operation, resulting in reduced stability; and the polymer polymer layer is also prone to aging during repeated temperature changes, resulting in reduced stability.

[0004] In summary, to solve the above problems, it is of great significance to prepare a functional current collector with high energy density and good stability. Summary of the Invention

[0005] The purpose of the present invention is to provide a method for preparing a functional current collector at low temperature using a polymer to solve the problems raised in the prior art.

[0006] To achieve the above purpose, the present invention provides the following technical solutions: A method for preparing a functional current collector at low temperature using a polymer, comprising the following steps: S1: Clean the surface of the base film to obtain a pretreated base film; S2: Mix the monomer solution, the functional substance solution, and the radical initiator solution evenly to obtain a mixed solution; S3: Coat the mixed solution on the surface of the pretreated base film, irradiate it with low-temperature plasma, stand at room temperature, wash, and dry to form a polymer layer to obtain a current collector base film; S4: Deposit a metal layer on the polymer layer surface of the current collector base film to obtain a functional current collector.

[0007] Preferably, the volume ratio of the monomer solution, the functional substance solution, and the radical initiator solution is 67-84:15-30:1-3.

[0008] Preferably, the monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution with a volume ratio of 30-40:20-30:30-40; The concentration of the acrylic acid solution is 0.45-0.55 mol / L; the concentration of the perfluorooctylethyl acrylate solution is 0.15-0.25 mol / L; the concentration of the styrene solution is 0.25-0.35 mol / L.

[0009] The preparation method of the monomer solution includes the following steps: separately prepare the acrylic acid solution, the perfluorooctylethyl acrylate solution, and the styrene solution; mix the acrylic acid solution, the perfluorooctylethyl acrylate solution, and the styrene solution evenly to obtain the monomer solution.

[0010] Preferably, the functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution with a volume ratio of 5-10:8-15:2-5; The concentration of the carbon nanotube solution is 0.9-1.1 g / L; the concentration of the triphenyl phosphate solution is 4.8-5.2 g / L; the concentration of the antioxidant 1010 solution is 0.1-0.2 g / L.

[0011] The preparation method of the functional substance solution includes the following steps: separately prepare the carbon nanotube solution, the triphenyl phosphate solution, and the antioxidant 1010 solution; magnetically stir the carbon nanotube solution, the triphenyl phosphate solution, and the antioxidant 1010 solution for 30-40 min to obtain the functional substance solution.

[0012] Preferably, the radical initiation solution is an azobisisobutyronitrile solution with a concentration of 0.01-0.02 mol / L.

[0013] Among them, in the monomer solution, monomers with specific functional groups can be selected according to the actual required functional characteristics. For example, if hydrophilicity needs to be improved, monomers containing functional groups such as hydroxyl (-OH) and carboxyl (-COOH), such as acrylic acid (AA), can be selected; if hydrophobicity needs to be improved, monomers containing fluorine atoms or long-chain alkyl groups, such as perfluorooctylethyl acrylate (PFOEA), can be selected; if chemical stability needs to be improved, monomers containing stable structures such as benzene rings, such as styrene (St), can be selected. The selected monomers need to be purified to remove impurities and inhibitors.

[0014] Among them, in the functional substance solution, conductive fillers (such as carbon nanotubes), flame retardants (such as phosphate esters), and antioxidants (such as hindered phenols) can be selected. Before preparing the solution, the flame retardant and antioxidant need to be dried to remove moisture. The conductive filler needs to be surface-treated to improve its dispersibility in the polymerization system; that is, ultrasonic dispersion treatment. When ultrasonic waves propagate in a liquid, cavitation effects will occur, forming tiny bubbles. When these bubbles burst, powerful shock waves and microjets will be generated, which can effectively break the agglomeration between conductive filler particles and make them evenly dispersed in the solution.

[0015] Among them, the specific process of surface treatment of the conductive filler is as follows: Add the conductive filler to a suitable solvent (N-dimethylformamide (DMF)) to form a suspension. Then place the suspension in an ultrasonic cleaner or an ultrasonic cell disruptor for ultrasonic treatment. The ultrasonic power and time are adjusted according to the type and concentration of the filler. Generally, the ultrasonic power can be set to 100 - 500 W, and the ultrasonic time is 0.5 - 2 hours. During the ultrasonic treatment process, the suspension can be appropriately stirred to improve the dispersion effect.

[0016] Among them, during the solution mixing process, magnetic stirring or ultrasonic dispersion methods need to be used to ensure that each component is fully mixed and to avoid agglomeration or stratification phenomena. The mixing ratio is optimized and determined according to the required functional characteristics and the performance requirements of the polymer layer. For example, if it is necessary to improve hydrophilicity and conductivity simultaneously, the proportion of monomers containing hydrophilic functional groups and conductive fillers can be appropriately increased.

[0017] Among them, when mixing the solution, attention should be paid to the addition order and stirring method of the solution to avoid phenomena such as agglomeration and precipitation, which will affect the performance of the material. Different experimental conditions (such as temperature, reaction time, etc.) will also affect the performance of the material, and these factors need to be comprehensively considered for adjustment.

[0018] More optimally, during the low-temperature plasma irradiation process: the gas atmosphere is an inert gas, and the temperature is -20~5°C; in the irradiation process, first irradiate once at a power of 140~160 W for 5~8 min, and then irradiate twice at a power of 250~300 W for 3~5 min.

[0019] More optimally, during the low-temperature plasma irradiation process, the temperature is -20~5°C, and the environmental vacuum degree before work is 5.0×10 -3 Pa; during the working process, the working gases are argon and nitrogen, the argon gas flow rate is 100 sccm ± 10, the nitrogen gas flow rate is 50 sccm ± 10, and the environmental vacuum degree during work is 1.0×10 -3 ~2.0×10 -3 Pa; During the standing process, the time is 60~80 min; During the washing process, the washing solution includes, but is not limited to, ethanol; During the drying process, the optimized solution is infrared heating, with the heating temperature being 50 - 60°C and the winding speed after drying being 4 - 6 m / min.

[0020] Among them, plasma low-temperature irradiation is carried out in a low-temperature environment (-20°C to 5°C). High-energy particles (electrons, ions, free radicals, etc.) in the plasma collide with monomer molecules to initiate the polymerization reaction of the monomers, forming a polymer layer. By precisely controlling the polymerization conditions, the growth and arrangement of polymer molecules can be affected, thereby achieving precise control of the microstructure (such as pore size distribution, porosity, etc.).

[0021] Among them, in the present invention, the base film coated with the mixed solution is placed in a low-temperature environment, and then through a plasma low-temperature irradiation device, the monomers are induced to carry out an in-situ polymerization reaction on the surface of the base film. During the polymerization process, the monomer molecules start chain growth and cross-linking reactions under the action of the initiator, gradually forming a polymer layer. The polymerization time is controlled according to the type, concentration of the initiator and the rate of the polymerization reaction.

[0022] Among them, before polymerization, ensure the normal operation of the vacuum system, gas supply system, power supply system, etc. of the equipment. Select appropriate working gases according to the required microstructure and polymer properties. For example, argon can provide an inert environment, which helps to reduce oxidation reactions, and the gas flow is precisely controlled by a mass flow controller. Nitrogen can introduce nitrogen-containing functional groups to change the chemical properties of the polymer, and the gas flow is precisely controlled by a mass flow controller. And the magnitude of the pressure in the process will affect the density and distribution of the plasma, thereby affecting the rate of the polymerization reaction and the microstructure of the polymer. At a lower pressure, the high-energy particles in the plasma have higher energy, which is beneficial to initiating the polymerization reaction, but may lead to an increase in porosity; at a higher pressure, particle collisions are frequent, and the polymer grows more uniformly, but the pore size may be smaller.

[0023] Among them, by adjusting the power of the plasma generator, the energy and density of the plasma are controlled. The power is generally between 100 - 300 W, and the specific value is optimized according to the properties of the solution and the required polymerization rate. A higher power can accelerate the polymerization reaction rate, but may cause damage to the coating surface; a lower power results in a slower polymerization reaction, but is beneficial to forming a more uniform microstructure. The present invention performs multi-step plasma treatment and changes the process parameters in different steps. For example, in the first step, plasma treatment with a lower power is used to preliminarily polymerize the monomers to form a core structure; in the second step, the power is increased to further grow and cross-link the core structure to form the required pore size and porosity. By reasonably designing the parameters of the multi-step treatment, fine control of the microstructure can be achieved.

[0024] After the polymerization reaction is completed, the functional collective fluid needs to be taken out of the low-temperature environment and left at room temperature for a period of time to fully cool and stabilize. Then, the functional collective fluid is cleaned to remove impurities such as residual solvents and unreacted monomers on the surface.

[0025] Preferably, during the coating process: the temperature is 20~25°C, the relative humidity is 40~60%; the coating method is knife coating, the distance between the knife and the pretreated base film is 1μm ± 0.1, the winding speed is 15~25m / min, the unwinding tension is 160~200N, the winding tension is 200~240N; the infusion speed of the mixed solution is 5~10mL / min, and the coating thickness is 1μm ± 0.1.

[0026] Preferably, the base film is a PET base film with a thickness of 6 ± 0.1μm; the preparation method of the pretreated base film specifically includes the following steps: putting the base film into a vacuum winding device, adjusting the winding speed to 14~16m / min, the unwinding tension to 95~105N, the winding tension to 175~185N, and under a vacuum degree of 5.0×10 -3 Pa, cleaning both sides of the base film with a plasma source at a power of 1600~1800W, and breaking the vacuum to obtain the pretreated base film.

[0027] Before coating, it is necessary to ensure that the PET base film is clean without impurities and wrinkles, and its width and length meet the specifications of the winding machine. It is also necessary to conduct a comprehensive inspection and debugging of the winding machine, including the unwinding device, winding device, tension control system, knife coating device, etc. According to the material and thickness of the PET base film, set appropriate unwinding and winding tensions to ensure that the base film runs smoothly without stretching deformation during operation. Adjust the height of the knife of the knife coating device, and precisely control the gap between the knife and the surface of the base film using a thickness calibrator. At the same time, check the flatness and cleanliness of the coating head to ensure that the solution can be extruded evenly Among them, the coating method can also be selected from knife coating, spin coating, spraying, etc., and a suitable coating method is selected according to the size and shape of the base film and the required thickness of the polymer layer. At the same time, it is also necessary to control the coating thickness to ensure that the thickness of the polymer layer is uniform.

[0028] During the coating process, it is necessary to monitor the tension and coating thickness in real time and adjust them in time if there are deviations.

[0029] After coating, conduct an appearance inspection of the coating before winding to observe whether there are defects such as bubbles, scratches, and uneven thickness. If minor defects are found, local repair can be carried out before the coating is cured; if the defects are serious, production needs to be stopped, the reasons are investigated, and the equipment and process parameters are adjusted.

[0030] Preferably, the metal layer includes one of a copper layer and an aluminum layer; the thickness is 850~950nm.

[0031] More preferably, the preparation process of the copper layer specifically includes the following steps: placing the current collector base film into the chamber of a vacuum magnetron winding coating equipment, turning on the vacuum pump, and pumping the vacuum degree in the chamber to 5.0×10 -3 Pa; introducing argon gas, adjusting the flow rate to 200±10 sccm, applying a DC voltage of 1000±10 V between the copper target and the current collector base film, setting the copper target power to 8~10 kW (for 8 pairs of copper targets, the power of each pair of target materials is 8~10 kW), and depositing a copper layer on the surface of the current collector base film at a coating speed of 2.8~3.2 m / min to obtain a functional current collector.

[0032] More preferably, the preparation method of the aluminum layer includes the following steps: placing the base film into the chamber of a vacuum winding evaporation coating equipment, evacuating to 5.0×10 -3 Pa; heating the evaporation boat, depositing an aluminum layer at a heating power of 75~85%, a wire feeding speed of 360~380 mm / min, a coating speed of 9~11 m / min, a unwind tension of 195~205 N, and a rewind tension of 235~245 N to obtain a functional current collector.

[0033] In summary, the features of the present invention are as follows: Material customization: According to different performance requirements, monomers and additives can be accurately selected and designed to achieve the customization of the performance of the polymer layer. For example, introducing monomers with specific functional groups can make the polymer layer have better hydrophilicity, hydrophobicity or chemical stability, etc., to adapt to different application environments and battery systems; Enhanced interface bonding: During the in-situ polymerization process, the polymer monomers directly polymerize on the surface of the substrate, which can form a closer and more stable chemical bonding or physical adsorption with the substrate, greatly improving the bonding force between the polymer layer and the substrate and reducing the possibility of delamination, peeling, etc. during use; Multi-functional integration: A variety of functional substances, such as conductive fillers, flame retardants, antioxidants, etc., can be simultaneously introduced into the polymerization system, so that the functional current collector has basic functions such as conductivity and load-bearing while also having multiple additional functions such as good conductivity, flame retardancy, and antioxidant properties, improving the comprehensive performance of the battery; Microstructure regulation: By controlling the conditions of low-temperature in-situ polymerization, such as reaction time, initiator concentration, monomer concentration, etc., the microstructure of the polymer layer can be accurately regulated, such as achieving a nano-level pore size distribution and porosity control, which is beneficial to the transmission of lithium ions and the infiltration of the electrolyte, improving the charge and discharge performance of the battery.

[0034] Compared with the prior art, the beneficial effects of the present application are as follows: By introducing monomers with specific functional groups and a variety of functional substances, and precisely controlling their concentrations and ratios, the polymer layer has better hydrophilicity, hydrophobicity, chemical stability and other properties. Furthermore, the process is further optimized, thereby improving the comprehensive performance of the functional current collector. The preparation method is simple to operate and easy to control, and has good application prospects. Detailed implementation manners

[0035] Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0036] It should be noted that there are no special restrictions on the purchase manufacturers of all raw materials involved in the present invention. Exemplarily, it includes: PET base film with a thickness of 6 μm; CAS number of acrylic acid: 79-10-7; CAS number of perfluorooctylethyl acrylate: 27905-45-9; CAS number of styrene: 100-42-5; carbon nanotubes with an aspect ratio of 1000 - 3000 and a particle size of 10 - 20 nm; CAS number of triphenyl phosphate: 115-86-6; CAS number of antioxidant 1010: 6683-19-8; CAS number of azobisisobutyronitrile: 78-67-1.

[0037] Among them, in the following embodiments, parts are parts by mass, and the above-mentioned and other unmentioned raw materials are all commercially available.

[0038] Among them, the preparation processes of each solution are as follows: Preparation of acrylic acid solution: Dissolve 3.6 g of purified acrylic acid in ethanol, transfer it to a 100 mL volumetric flask and make up to the mark to obtain an acrylic acid solution with a concentration of 0.05 mol / L.

[0039] Preparation of perfluorooctylethyl acrylate solution: Dissolve 25 g of purified perfluorooctylethyl acrylate in acetone, transfer it to a 250 mL volumetric flask and make up to the mark to obtain a perfluorooctylethyl acrylate solution with a concentration of 0.2 mol / L.

[0040] Preparation of styrene solution: Dissolve 4.68 g of purified styrene in toluene, transfer it to a 150 mL volumetric flask and make up to the mark to obtain a styrene solution with a concentration of 0.3 mol / L.

[0041] Preparation of carbon nanotube solution: Add 0.2 g of carbon nanotubes to N,N-dimethylformamide, perform ultrasonic dispersion treatment at a power of 400 W for 90 min, transfer it to a 200 mL volumetric flask and make up to the mark to obtain a carbon nanotube solution with a concentration of 1 g / L.

[0042] Preparation of triphenyl phosphate solution: 0.5 g of dried triphenyl phosphate was added to chloroform for dissolution, and then transferred to a 100 mL volumetric flask and made up to the mark to obtain a triphenyl phosphate solution with a concentration of 5 g / L.

[0043] Preparation of antioxidant 1010 solution: 0.015 g of dried antioxidant 1010 was added to ethanol for dissolution, and then transferred to a 150 mL volumetric flask and made up to the mark to obtain an antioxidant 1010 solution with a concentration of 0.1 g / L.

[0044] Preparation of free radical initiator solution: 0.164 g of azobisisobutyronitrile was added to acetone for dissolution, and then transferred to a 50 mL volumetric flask and made up to the mark to obtain a free radical initiator solution with a concentration of 0.02 mol / L.

[0045] Among them, in each example and comparative example, the base film is a PET base film with a thickness of 6 μm.

[0046] Example 1: The method for preparing a functional current collector at low temperature of a polymer includes the following steps: S1: The base film was placed in a vacuum winding device, the winding speed was adjusted to 15 m / min, the unwinding tension was 100 N, the winding tension was 180 N, and under a vacuum degree of 5.0×10 -3 Pa, the two sides of the base film were cleaned with a plasma source at a power of 1800 W, and the vacuum was broken to obtain a pretreated base film; S2: The monomer solution, the functional substance solution, and the free radical initiator solution were mixed evenly at a volume ratio of 77:21:2 to obtain a mixed solution; among them, the monomer solution included an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution at a volume ratio of 40:30:30; the functional substance solution included a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution at a volume ratio of 8:10:3; S3: The pretreated base film was installed on the unwinding device of the winding machine table, and the base film was introduced into the scraping area with an unwinding tension of 180 N through a guide roller to ensure that the base film passed smoothly under the doctor blade. The height of the doctor blade of the scraping device was adjusted in advance, and the gap between the doctor blade and the surface of the base film was precisely controlled to be 1 μm by a thickness calibrator; the mixed solution was poured into the solution tank of the coating head, and the solution was transported to the coating area in front of the doctor blade at a stable flow rate by an infusion pump, and the flow rate was controlled at 8 mL / min. At a temperature of 25 °C and a relative humidity of 50%, the winding machine table was started, the winding speed was set to 20 m / min, and the coated base film was collected with a winding tension of 220 N. After passing the inspection, it was transferred to a radio frequency plasma generator, at a temperature of -15 °C and a vacuum degree of 5.0×10 -3Under a pressure of Pa, argon with a gas flow rate of 100 sccm and nitrogen with a gas flow rate of 50 sccm are introduced. First, irradiate once at a power of 150 W for 5 min, and then irradiate twice at a power of 300 W for 3 min. After the polymerization reaction is completed, turn off the plasma generator, let it stand at room temperature for 60 min, take it out, wash it with ethanol, and then complete drying and winding at a winding speed of 5 m / min under infrared low-temperature heating at 55 °C to obtain a current collector base film; S4: Place the current collector base film into the chamber of a vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; Introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, each pair of target materials has a power of 10 KW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0047] Example 2: The method for preparing a functional current collector by polymer low-temperature includes the following steps: S1: Place the base film into a vacuum winding equipment, adjust the winding speed to 15 m / min, the unwind tension to 100 N, and the winding tension to 180 N. Under a vacuum degree of 5.0×10 -3 Pa, use a plasma source to clean both sides of the base film at a power of 1800 W, break the vacuum, and obtain a pretreated base film; S2: Mix the monomer solution, the functional substance solution, and the free radical initiator solution evenly at a volume ratio of 77:21:2 to obtain a mixed solution; wherein, the monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution at a volume ratio of 40:30:30; the functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution at a volume ratio of 8:10:3; S3: Install the pretreated base film on the unwind device of the winding machine table, introduce the base film into the coating area through a guide roller with an unwind tension of 180 N, ensure that the base film passes smoothly under the doctor blade, adjust the height of the doctor blade of the coating device in advance, and precisely control the gap between the doctor blade and the surface of the base film to be 1 μm using a thickness calibrator; Pour the mixed solution into the solution tank of the coating head, and convey the solution to the coating area in front of the doctor blade at a stable flow rate through an infusion pump, with the flow rate controlled at 8 mL / min. At a temperature of 25 °C and a relative humidity of 50%, start the winding machine table, set the winding speed to 20 m / min, and collect the coated base film with a winding tension of 220 N. After inspection and qualification, transfer it to a radio frequency plasma generator, at a temperature of -5 °C and a vacuum degree of 5.0×10 -3Under a pressure of Pa, argon with a gas flow rate of 100 sccm and nitrogen with a gas flow rate of 50 sccm are introduced. First, irradiate once at a power of 150 W for 5 min, and then irradiate twice at a power of 300 W for 3 min. After the polymerization reaction is completed, turn off the plasma generator, let it stand at room temperature for 60 min, take it out, wash it with ethanol, and then complete drying and winding at a winding speed of 5 m / min under infrared low-temperature heating at 55 °C to obtain a current collector base film; S4: Place the current collector base film into the chamber of a vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; Introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, and the power of each pair of target materials is 10 kW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0048] Example 3: A method for preparing a functional current collector at low temperature by polymerization includes the following steps: S1: Place the base film into a vacuum winding equipment, adjust the winding speed to 15 m / min, the unwinding tension to 100 N, and the winding tension to 180 N. Under a vacuum degree of 5.0×10 -3 Pa, use a plasma source to clean both sides of the base film at a power of 1800 W, and break the vacuum to obtain a pretreated base film; S2: Mix the monomer solution, the functional substance solution, and the free radical initiator solution evenly at a volume ratio of 77:21:2 to obtain a mixed solution; wherein, the monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution at a volume ratio of 50:25:25; the functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution at a volume ratio of 8:10:3. S3: Install the pretreated base film on the unwinding device of the winding machine table, introduce the base film into the coating area with an unwinding tension of 180 N through a guide roller, ensure that the base film passes smoothly under the doctor blade, adjust the height of the doctor blade of the coating device in advance, and precisely control the gap between the doctor blade and the surface of the base film to be 1 μm using a thickness calibrator; Pour the mixed solution into the solution tank of the coating head, and use an infusion pump to transport the solution to the coating area in front of the doctor blade at a stable flow rate, with the flow rate controlled at 8 mL / min. At a temperature of 25 °C and a relative humidity of 50%, start the winding machine table, set the winding speed to 20 m / min, and collect the coated base film with a winding tension of 220 N. After passing the inspection, transfer it to a radio frequency plasma generator, at a temperature of -15 °C and a vacuum degree of 5.0×10 -3Under a pressure of Pa, argon with a gas flow rate of 100 sccm and nitrogen with a gas flow rate of 50 sccm are introduced. First, irradiate once at a power of 150 W for 5 min, and then irradiate twice at a power of 300 W for 3 min. After the polymerization reaction is completed, turn off the plasma generator, let it stand at room temperature for 60 min, take it out, wash it with ethanol, and then complete drying and winding at a winding speed of 5 m / min under infrared low-temperature heating at 55 °C to obtain a current collector base film; S4: Place the current collector base film into the chamber of a vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; Introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, each pair of target materials has a power of 10 KW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0049] Example 4: A method for preparing a functional current collector by polymer low temperature includes the following steps: S1: Place the base film into a vacuum winding equipment, adjust the winding speed to 15 m / min, the unwinding tension to 100 N, and the winding tension to 180 N. Under a vacuum degree of 5.0×10 -3 Pa, use a plasma source to clean both sides of the base film at a power of 1800 W, break the vacuum, and obtain a pretreated base film; S2: Mix the monomer solution, the functional substance solution, and the free radical initiator solution evenly at a volume ratio of 77:21:2 to obtain a mixed solution; wherein, the monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution at a volume ratio of 30:40:40; the functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution at a volume ratio of 8:10:3; S3: Install the pretreated base film on the unwinding device of the winding machine table, introduce the base film into the coating area with an unwinding tension of 180 N through a guide roller, ensure that the base film passes smoothly under the doctor blade, adjust the height of the doctor blade of the coating device in advance, and precisely control the gap between the doctor blade and the surface of the base film to be 1 μm using a thickness calibrator; Pour the mixed solution into the solution tank of the coating head, and use an infusion pump to transport the solution to the coating area in front of the doctor blade at a stable flow rate, with the flow rate controlled at 8 mL / min. At a temperature of 25 °C and a relative humidity of 50%, start the winding machine table, set the winding speed to 20 m / min, and collect the coated base film with a winding tension of 220 N. After inspection and passing, transfer it to a radio frequency plasma generator, at a temperature of -15 °C and a vacuum degree of 5.0×10 -3Under a pressure of Pa, argon with a gas flow rate of 100 sccm and nitrogen with a gas flow rate of 50 sccm are introduced. First, irradiate once at a power of 150 W for 5 min, and then irradiate twice at a power of 300 W for 3 min. After the polymerization reaction is completed, turn off the plasma generator, let it stand at room temperature for 60 min, take it out, wash it with ethanol, and then complete drying and winding at a winding speed of 5 m / min under infrared low-temperature heating at 55 °C to obtain a current collector base film; S4: Place the current collector base film into the chamber of a vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; Introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, each pair of target materials has a power of 10 KW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0050] Comparative Example 1: Based on Example 1, directly sputter a copper layer on the surface of the pretreated current collector base film, and the rest of the process remains unchanged. Specifically as follows: S1: Place the base film into a vacuum winding equipment, adjust the winding speed to 15 m / min, the unwinding tension to 100 N, and the winding tension to 180 N. Under a vacuum degree of 5.0×10 -3 Pa, use a plasma source to clean both sides of the base film at a power of 1800 W, break the vacuum, and obtain a pretreated base film; S2: Place the pretreated base film into the chamber of a vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; Introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, each pair of target materials has a power of 10 KW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0051] Comparative Example 2: Based on Example 1, during the process of plasma low-temperature irradiation, irradiate at 300 W throughout the process, and the rest of the process remains unchanged. Specifically as follows; S1: Place the base film into a vacuum winding equipment, adjust the winding speed to 15 m / min, the unwinding tension to 100 N, and the winding tension to 180 N. Under a vacuum degree of 5.0×10 -3 Pa, use a plasma source to clean both sides of the base film at a power of 1800 W, break the vacuum, and obtain a pretreated base film; S2: Mix the monomer solution, functional substance solution, and free radical initiator solution evenly at a volume ratio of 77:21:2 to obtain a mixed solution. Among them, the monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution at a volume ratio of 40:30:30. The functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution at a volume ratio of 8:10:3. S3: Install the pretreated base film on the unwinding device of the winding machine. Introduce the base film into the scraping area with a unwinding tension of 180 N through a guiding roller to ensure that the base film passes smoothly under the scraper. Adjust the height of the scraper of the scraping device in advance, and use a thickness calibrator to precisely control the gap between the scraper and the surface of the base film to be 1 μm. Pour the mixed solution into the solution tank of the coating head, and use an infusion pump to transport the solution to the coating area in front of the scraper at a stable flow rate. The flow rate is controlled at 8 mL / min. At a temperature of 25°C and a relative humidity of 50%, start the winding machine, set the winding speed to 20 m / min, and collect the coated base film with a winding tension of 220 N. After passing the inspection, transfer it to a radio frequency plasma generator. At a temperature of -15°C and a vacuum degree of 5.0×10 -3 Pa, introduce argon with a gas flow rate of 100 sccm and nitrogen with a gas flow rate of 50 sccm, and irradiate with a power of 300 W for 8 min. After the polymerization reaction is completed, turn off the plasma generator, let it stand at room temperature for 60 min, take it out, wash it with ethanol, and then complete drying and winding at a winding speed of 5 m / min under infrared low-temperature heating at 55°C to obtain a current collector base film. S4: Place the current collector base film into the chamber of a vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; Introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, each pair of target materials has a power of 10 KW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0052] Comparative Example 3: Based on Example 1, replace the process of plasma low-temperature irradiation with room-temperature ultraviolet light initiation, and the rest of the processes remain unchanged. Specifically as follows; S1: Place the base film into a vacuum winding equipment, adjust the winding speed to 15 m / min, the unwinding tension to 100 N, and the winding tension to 180 N. At a vacuum degree of 5.0×10 -3 Pa, use a plasma source to clean both sides of the base film with a power of 1800 W, break the vacuum, and obtain a pretreated base film. S2: Mix the monomer solution, functional substance solution, and free radical initiator solution evenly at a volume ratio of 77:21:2 to obtain a mixed solution; wherein, the monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution at a volume ratio of 40:30:30; the functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution at a volume ratio of 8:10:3. S3: Install the pretreated base film on the unwinding device of the winding machine table, introduce the base film into the scraping area with a unwinding tension of 180 N through a guiding roller, ensure that the base film passes smoothly under the scraper, adjust the height of the scraper of the scraping device in advance, and precisely control the gap between the scraper and the surface of the base film to be 1 μm using a thickness calibrator; pour the mixed solution into the solution tank of the coating head, and convey the solution to the coating area in front of the scraper at a stable flow rate through an infusion pump. The flow rate is controlled at 8 mL / min. At a temperature of 25°C and a relative humidity of 50%, start the winding machine table, set the winding speed to 20 m / min, and collect the coated base film with a winding tension of 220 N. After passing the inspection, at a temperature of 25°C and a vacuum degree of 5.0×10 -3 Pa, introduce argon with a gas flow rate of 100 sccm and nitrogen with a gas flow rate of 50 sccm, and irradiate with ultraviolet light for 5 min; take out, wash with ethanol, and then complete drying and winding at a winding speed of 5 m / min under infrared low-temperature heating at 55°C to obtain a current collector base film. S4: Place the current collector base film into the chamber of the vacuum magnetron winding coating equipment, turn on the vacuum pump, and pump the vacuum degree in the chamber to 5.0×10 -3 Pa; introduce argon, adjust the flow rate to 200 sccm, apply a DC voltage of 1000 V between the copper target and the current collector base film, set the copper target power to 10 kW (8 pairs of copper targets, each pair of target materials has a power of 10 KW), and deposit a copper layer on the surface of the current collector base film at a coating speed of 3 m / min to obtain a functional current collector.

[0053] Performance test: Apply the functional current collectors prepared in each example and comparative example to the battery, and conduct the following tests respectively: (1) Battery performance test: Measure the capacity and mass of the battery, and calculate the energy density; through a charge-discharge tester, test the efficiency of the battery at a 1C charge-discharge rate, record the charge-discharge time and capacity loss; test the capacity retention rate of the battery at a 2C charge-discharge rate. (2) Safety performance test: Use an infrared thermal imager and a differential scanning calorimeter (DSC) to monitor the thermal behavior of the battery in different temperature environments, record the thermal runaway temperature and heat release rate; simulate the internal short circuit situation of the battery, observe the reaction of the battery, and record the short circuit current and whether safety accidents such as fire and explosion occur.

[0054] (3)Material property testing: Measure the contact angle of the surface of the functional current collector using a contact angle measuring instrument to evaluate its hydrophilicity; measure the surface resistance of the functional current collector using a four-probe tester to evaluate its electrical conductivity; conduct a flame retardancy test according to the UL94 vertical burning test in GB / T 2408-2021 to evaluate the flame retardancy grade of the functional current collector; place the functional current collector at a temperature of 120 °C, an oxygen concentration of 80%, and an atmospheric pressure of 1 atmosphere for 100 h, measure its mass change and performance change, and evaluate its antioxidant performance; use a tensile test to measure the bonding strength between the polymer layer and the base film to evaluate the interfacial bonding strength; the experimental data are shown in Table 1.

[0055]

[0056] Conclusion: As can be seen from Table 1: Since the functional current collector of the present invention uses a polymer intermediate layer with a lower density and can be made thinner, it can accommodate more active substances in the battery, and the energy density is significantly improved, meeting the invention purpose of improving the energy density of the battery; the polymer layer formed by in-situ polymerization has good uniformity and controllable microstructure, which is beneficial to lithium ion transmission, reduces the ion transmission resistance, and improves the charge and discharge efficiency of the battery, achieving the purpose of optimizing the charge and discharge efficiency; the functional current collector enables the battery to maintain a high capacity during high-rate charge and discharge, has better fast charge and discharge capabilities, and meets the requirements for the rate performance of the battery in the invention; the polymer layer of the functional current collector has good thermal stability, can withstand higher temperatures, reduces the risk of battery thermal runaway, and enhances the thermal safety of the battery; the polymer layer in the functional current collector plays an isolation and buffering role when the metal layer is damaged, effectively inhibits the short-circuit risk, and improves the safety performance of the battery; the introduction of monomers containing hydrophilic functional groups makes the functional current collector have good hydrophilicity, which is beneficial to the infiltration of the electrolyte and lithium ion transmission; the addition of conductive fillers and through a reasonable process makes the functional current collector have good electrical conductivity, meeting the basic functional requirements of the current collector; the addition of a flame retardant makes the functional current collector reach a high flame retardancy grade, enhancing the safety of the battery in case of fire. The role of the antioxidant makes the functional current collector have a small mass change and stable performance in a high-temperature and high-oxygen environment, extending the service life of the battery; in-situ polymerization makes the polymer layer and the base film form a tight and stable bond, with strong bonding strength, reducing the possibility of delamination and peeling, and ensuring the structural stability of the functional current collector.

[0057] In Comparative Example 1, a copper layer was directly sputtered on the surface of the pretreated current collector base film, so the interfacial property with the base film was poor and the comprehensive performance decreased; in Comparative Example 2, during the low-temperature plasma irradiation process, the irradiation treatment was carried out at 300 W throughout the process, resulting in excessive etching of the material surface, damaging the formed nuclear structure and causing the degradation of the microstructure, so the comprehensive performance decreased; in Comparative Example 3, the low-temperature plasma irradiation process was replaced by ultraviolet light initiation at room temperature, making it difficult to achieve fine control of the microstructure, such as pore size and porosity, and the reaction rate and depth initiated were relatively difficult to control, so the comprehensive performance decreased.

[0058] In summary, the present invention introduces monomers with specific functional groups and various functional substances, precisely controls their concentrations and ratios, enables the polymer layer to have better hydrophilicity, hydrophobicity, chemical stability and other properties, and further optimizes the process, thereby improving the comprehensive performance of the functional current collector. The preparation method is simple to operate and easy to control, and has good application prospects.

[0059] Finally, it should be noted that the above are only the preferred embodiments of the present invention and are not used to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some of the technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for preparing a functional current collector at low temperature of a polymer, characterized in that: It includes the following steps: S1: Clean the surface of the base film to obtain a pretreated base film; S2: Mix the monomer solution, the functional substance solution, and the radical initiator solution evenly to obtain a mixed solution; S3: Coat the mixed solution on the surface of the pretreated base film, perform low-temperature plasma irradiation, stand at room temperature, wash, and dry to form a polymer layer to obtain a current collector base film; S4: Deposit a metal layer on the polymer layer surface of the current collector base film to obtain a functional current collector.

2. The method for preparing a functional current collector at low temperature of a polymer according to claim 1, wherein: The volume ratio of the monomer solution, the functional substance solution, and the radical initiator solution is 67~84:15~30:1~3.

3. The method for preparing a functional current collector at low temperature using a polymer according to claim 2, characterized in that: The monomer solution includes an acrylic acid solution, a perfluorooctylethyl acrylate solution, and a styrene solution with a volume ratio of 30~40:20~30:30~40; The concentration of the acrylic acid solution is 0.45~0.55 mol / L; the concentration of the perfluorooctylethyl acrylate solution is 0.15~0.25 mol / L; the concentration of the styrene solution is 0.25~0.35 mol / L.

4. A method for preparing a functional current collector at low temperature of a polymer according to claim 2, characterized in that: The functional substance solution includes a carbon nanotube solution, a triphenyl phosphate solution, and an antioxidant 1010 solution with a volume ratio of 5~10:8~15:2~5; The concentration of the carbon nanotube solution is 0.9~1.1 g / L; the concentration of the triphenyl phosphate solution is 4.8~5.2 g / L; the concentration of the antioxidant 1010 solution is 0.1~0.2 g / L.

5. The method for preparing a functional current collector at low temperature of a polymer according to claim 2, wherein: The radical initiator solution is an azobisisobutyronitrile solution with a concentration of 0.01~0.02 mol / L.

6. A method for preparing a functional current collector at low temperature using a polymer according to claim 1, characterized in that: During the low-temperature plasma irradiation: the gas atmosphere is an inert gas, and the temperature is -20~5°C; in the irradiation process, first irradiate once at a power of 140~160 W for 5~8 min, and then irradiate twice at a power of 250~300 W for 3~5 min.

7. A method for preparing a functional current collector at low temperature of a polymer according to claim 1, characterized in that: During the coating process: the temperature is 20~25°C, and the relative humidity is 40~60%; the coating method is knife coating, the distance between the knife and the pretreated base film is 1 μm ± 0.1, the winding speed is 15~25 m / min, the unwinding tension is 160~200 N, and the winding tension is 200~240 N; the infusion speed of the mixed solution is 5~10 mL / min, and the coating thickness is 1 μm ± 0.

1.

8. A method for preparing a functional current collector at low temperature using a polymer according to claim 1, characterized in that: The base film is a PET base film with a thickness of 6 ± 0.1 μm; the preparation method of the pretreated base film specifically includes the following steps: putting the base film into a vacuum winding device, adjusting the winding speed to 14 - 16 m / min, the unwinding tension to 95 - 105 N, and the winding tension to 175 - 185 N. Under a vacuum degree of 5.0×10 -3 Pa, using a plasma source to clean both sides of the base film at a power of 1600 - 1800 W, and breaking the vacuum to obtain the pretreated base film.

9. A method for preparing a functional current collector at low temperature using a polymer according to claim 1, characterized in that: The metal layer includes one of a copper layer and an aluminum layer; the thickness is 850~950 nm.

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