Preparation Method and Application of a Current Collector with High Binding Force

Abstract

The present invention relates to the field of composite current collectors, and specifically discloses a preparation method and application of a current collector with high bonding strength; the preparation method includes the following steps: S1: Take an aluminum oxide ultra-thin porous nanoplank and a metal foil, wash them; cut them into square chips; S2: Uniformly coat a solid lubricant on the aluminum oxide ultra-thin porous nanoplank, place it above the metal foil, and perform ultrasonic imprinting to obtain an aluminum oxide ultra-thin porous nanoplank / substrate with metal rods; S3: Immerse the aluminum oxide ultra-thin porous nanoplank / substrate stack obtained in step S2 in a NaOH solution to obtain a metal substrate with nanowires exposed; S4: Use nano laser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires; S5: Uniformly scrape and coat a conductive adhesive on the surface of the polymer film, spray the nanowires, and cure them under the conditions of an ultraviolet light intensity of 50-200 mW / cm² and a temperature of 110-120 °C to obtain a current collector.

Description

Technical Field

[0001] The present invention relates to the field of composite current collectors, and specifically discloses a preparation method and application of a current collector with high bonding strength. Background Art

[0002] With the rapid development of new energy and electronic technologies, the requirements for the cycle life, safety performance, and energy density of batteries are getting higher and higher. As an important part of the battery, the performance of the current collector directly affects the performance of the battery.

[0003] Currently, copper foils and aluminum foils are mostly used as current collectors for the positive and negative electrode sheets in lithium batteries and sodium batteries. Such current collectors have high costs and weights, which are not conducive to the control of battery costs and the improvement of energy density. In this regard, composite foils have obvious advantages compared with traditional foils. The composite foil current collector is usually a "sandwich" structure, with a polymer polymer layer in the inner layer and metal conductive layers on both sides. Since the metal layer on the surface of the composite current collector is thinner and the polymer layer inside is lighter, the overall weight of the current collector can be well reduced, and the energy density of the lithium-ion battery can be increased; at the same time, the thinner metal layer on the surface of the composite current collector is more likely to break than the current collector of the traditional foil when the lithium-ion battery undergoes thermal runaway, thereby isolating the connection between the active material and the current collector and preventing the continuous progress of the thermal runaway of the lithium-ion battery.

[0004] However, although the composite foil current collector has the advantages of low cost and light weight, a large amount of heat is generated during battery cycling, causing volume changes in the composite current collector. Excessive thermal shrinkage will cause large thermal deformation of the composite current collector. Most of the base film materials of the current composite current collector are made of PP (polypropylene) materials, and the bonding strength of PP materials is poor, which will lead to film surface deformation and copper layer peeling, seriously reducing the energy density and cycle life of the battery, and also bringing safety problems to the battery. Therefore, it is of great significance to study a preparation method of a current collector with high bonding strength. Summary of the Invention

[0005] The purpose of the present invention is to provide a preparation method and application of a current collector with high bonding strength to solve the problems raised in the above background art.

[0006] To solve the above technical problems, the present invention provides the following technical solution: A preparation method of a current collector with high bonding strength, including the following steps: S1: Take ultra-thin porous alumina nanoplates and metal foils, wash them (first wash with deionized water for 5 - 10 minutes, then wash with isopropanol for 5 - 10 minutes, and finally wash with ethanol for 5 - 10 minutes); cut them into square chips with side lengths of 1 - 5 mm.

[0007] S2: Coat the alumina ultra-thin porous nanoplates with a solid lubricant, place them above the metal foil, and perform ultrasonic imprinting using an ultrasonic imprinting device with a frequency of 15 - 25 kHz to obtain alumina ultra-thin porous nanoplates / substrates with metal rods.

[0008] S3: Immerse the alumina ultra-thin porous nanoplates / substrates obtained in step S2 in a 1M NaOH solution for 2 h to obtain metal substrates with nanowires exposed; for the nanowires, soak them in an aqueous solvent containing 1.5 wt% chromic acid and 6 wt% phosphoric acid for 3 h at an immersion temperature of 70 °C.

[0009] S4: Use nanolaser cutting technology to cut the nanowires on the metal substrate to obtain nanowires.

[0010] S5: Uniformly scrape and coat the surface of the polymer thin film with a conductive adhesive, control the surface temperature at 70 °C, and spray the nanowires; a nanowire dispersion liquid is used when spraying the nanowires, and the nanowire dispersion liquid is a 2 - 10 mg / ml nanowire ethanol dispersion liquid; the spraying speed is 10 - 20 mm / s; the atomization pressure is 5 - 30 MPa; the nozzle diameter is 50 - 200 μm; after spraying, cure for 5 min under the conditions of an ultraviolet light intensity of 50 - 200 mW / cm² and a temperature of 110 - 120 °C to obtain a current collector.

[0011] When spraying the nanowires, a nanowire ethanol dispersion liquid (dispersing the nanowires in ethanol) is used; if the concentration of the nanowires is too high, it may cause the nanowires to agglomerate, affecting the spraying effect; if the concentration is too low, it may not be possible to form a continuous and uniform coating.

[0012] The spraying speed of the nanowires affects the deposition rate and distribution uniformity of the nanowires; if the spraying speed is too fast, it may cause the nanowires not to have enough time to spread evenly, and if the speed is too slow, it may affect the production efficiency.

[0013] The atomization pressure for spraying the nanowires needs to be controlled. A suitable atomization pressure can fully atomize the nanowire suspension to form droplets with uniform sizes, thus ensuring the quality of the coating.

[0014] The nozzle size for spraying the nanowires affects the size of the droplets and the spraying flow rate. A smaller nozzle size can produce finer droplets, which is beneficial for forming a uniform coating, but may lead to a decrease in spraying efficiency; a larger nozzle size has the opposite effect, so a suitable nozzle size also needs to be selected.

[0015] Preferably, the preparation of the current collector comprises the following steps: uniformly scrape and coat a conductive adhesive on the surface of a polymer film, control the surface temperature at 70 °C, and spray nanowires; a nanowire dispersion is used when spraying the nanowires, and the nanowire dispersion is a 6 mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure for 5 min under the conditions of an ultraviolet light intensity of 75 mW / cm² and a temperature of 120 °C to obtain the current collector.

[0016] Preferably, the cleaning process is as follows: first clean with deionized water for 10 min, then clean with isopropanol for 10 min, and finally clean with ethanol for 10 min.

[0017] Preferably, the thickness of the ultra-thin porous alumina nanoplates is 500 - 800 nm; the nanopore size is 100 - 300 nm.

[0018] Preferably, the thickness of the ultra-thin porous alumina nanoplates is 600 nm.

[0019] Preferably, the size of the metal rod is 100 - 300 nm.

[0020] Preferably, the metal foil is a copper metal foil with a thickness of 100 μm.

[0021] Preferably, the solid lubricant is C60, and the coating thickness is 80 - 120 nm.

[0022] Preferably, the solid lubricant is C60, and the coating thickness is 100 nm.

[0023] Preferably, the polymer film is a BOPP polypropylene film with a thickness of 4 - 10 μm.

[0024] Preferably, the polymer film is a BOPP polypropylene film with a thickness of 5 μm (manufacturer: Jiadeli, model: 6014H).

[0025] Preferably, the thickness of the conductive adhesive is 0.8 - 1 μm.

[0026] Preferably, the thickness of the conductive adhesive is 1 μm.

[0027] Preferably, the polymer film is a modified polypropylene film, and the specific preparation method includes the following steps: S1: Mix hydroxyethyl methacrylate, polypropylene, and benzoyl peroxide, heat to 200-210°C, and react for 2-3 hours to obtain an intermediate; Take the intermediate, add it to N,N-dimethylformamide, stir evenly, add anhydrous sodium carbonate and bis(4-nitrophenyl) phosphate, heat to 180-190°C under a nitrogen atmosphere, react for 10-12 hours, and carry out reduced-pressure reflux to obtain modified polypropylene;

[0028] S2: Melt-extrude the modified polypropylene; Cast the obtained melt into a sheet, and successively carry out longitudinal stretching, transverse stretching, heat preservation, and corona treatment to obtain a modified polypropylene film.

[0029] Preferably, the intermediate includes the following raw materials, by mass: 15-20 parts of hydroxyethyl methacrylate, 100 parts of polypropylene, and 1-2 parts of benzoyl peroxide are mixed; The modified polypropylene includes the following raw materials, by mass: 100 parts of intermediate, 150-180 parts of N,N-dimethylformamide, 1-2 parts of anhydrous sodium carbonate, and 25-30 parts of bis(4-nitrophenyl) phosphate.

[0030] Preferably, the melt index of the polypropylene is 2.2 g / 10 min.

[0031] Preferably, the polypropylene is S51655 from Shanghai Yuanye.

[0032] Preferably, the specific preparation process of the modified polypropylene film includes the following steps: Melt-extrude the modified polypropylene; After casting the obtained melt into a sheet through a cooling roll and a high-pressure air knife, successively carry out longitudinal stretching and transverse stretching with a longitudinal stretching machine and a transverse stretching machine; The temperature of the cooling roll is 80-100°C, the gas temperature of the high-pressure air knife is 50-70°C, and the blowing speed is 130-150 m / s; The stretching temperature for longitudinal stretching is 130-150°C, the setting temperature is 140-160°C, preferably 150°C, and the stretching ratio is 5-8; The stretching temperature for transverse stretching is 150-170°C, the setting temperature is 170-180°C, and the stretching ratio is 7-13; Keep warm at 110-140°C for 3-5 minutes and carry out corona treatment; The corona power is 50-100 kW, and the linear speed is 50-300 m / min; Obtain a modified polypropylene film.

[0033] Preferably, the above current collector can be used to prepare a battery.

[0034] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: (1) The present invention prepares nanowires through ultrasonic imprinting, and then sprays the nanowires on the surface of a polymer film to prepare a composite current collector; the binding force between the nanowires and the polymer film is good, the polymer base film will not be thermally damaged during the process, and the internal stress is small, which can comprehensively improve the film surface quality. The nanowires are densely packed and stacked in a staggered manner. During the stretching process, the nanorods are interlaced and adhered to each other, without damaging the base film, and have strong tensile strength, which can reduce film fracture and reduce risks. The composite current collector prepared by this process can significantly improve the safety performance of the battery and increase the cycle life of the battery.

[0035] (2) The polymer film is a modified polypropylene film; during the modification process, first, under the action of an initiator, the hydrogen on the tertiary carbon of polypropylene is captured by free radicals to generate polypropylene macromolecular free radicals, then 2-hydroxyethyl methacrylate is grafted onto the side chain, and then bis(4-nitrophenyl) phosphate is grafted by the reaction of -OH and -NO2; the introduction of the benzene ring can improve the mechanical properties of polypropylene, and the phosphate group can induce the crystallization of polypropylene, making the arrangement of polypropylene molecular chains more regular, improving the mechanical properties, reducing fracture or deformation during the peeling process, and increasing the peeling force; the addition amount of 2-hydroxyethyl methacrylate needs to be controlled because too many side chains will also reduce the crystallinity of polypropylene, which is not conducive to the improvement of mechanical properties, and too few side chain grafts will result in an insignificant modification effect and little increase in the peeling force; the selection of polypropylene also has an important impact. Polypropylene with a small molecular weight has good crystallization performance but inferior mechanical properties compared to polypropylene with a large molecular weight, while too large a molecular weight of polypropylene will affect the crystallinity. Therefore, the selection of polypropylene also needs to be controlled; in summary, it is necessary to control the polypropylene type and the addition amount of each raw material to obtain a modified polypropylene film with good surface adhesion performance, good storage stability, and good mechanical properties, and improve the peeling strength. Specific Embodiments

[0036] The following is the preferred implementation mode of the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all embodiments. For those of ordinary skill in the art in this technical field, without departing from the principle of the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0037] Unless otherwise specified, the following parts are by mass;

[0038] Example 1: S1: Take an aluminum oxide ultra-thin porous nanoplates with a nanopore size of 130 nm and a 100-μm-thick metal copper foil. First, wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm;

[0039] S2: Coat the alumina ultra-thin porous nanoplates with a solid lubricant, place them above the metal foil, and perform ultrasonic imprinting using a Branson 2000X ultrasonic imprinting device with a device frequency of 20 kHz to obtain alumina ultra-thin porous nanoplates / substrates with copper metal rods sized 130 nm;

[0040] S3: Immerse the stack of alumina ultra-thin porous nanoplates / substrates obtained in step S2 in 1 M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed;

[0041] S4: Use nano laser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires;

[0042] S5: Uniformly scrape a 1-μm-thick conductive adhesive on the surface of the polypropylene film, spray the nanowires, and use a nanowire dispersion liquid when spraying the nanowires. The nanowire dispersion liquid is a 6-mg / ml nanowire ethanol dispersion liquid; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0043] Example 2: S1: Take alumina ultra-thin porous nanoplates with a nanopore size of 100 nm and a 100-μm-thick copper metal foil, first wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm;

[0044] S2: Coat the alumina ultra-thin porous nanoplates with a solid lubricant, place them above the metal foil, and perform ultrasonic imprinting using a Branson 2000X ultrasonic imprinting device with a device frequency of 20 kHz to obtain alumina ultra-thin porous nanoplates / substrates with copper metal rods sized 100 nm;

[0045] S3: Immerse the stack of alumina ultra-thin porous nanoplates / substrates obtained in step S2 in 1 M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed;

[0046] S4: Use nano laser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires;

[0047] S5: Uniformly scrape a 1-μm-thick conductive adhesive on the surface of the polypropylene film, spray the nanowires, and use a nanowire dispersion liquid when spraying the nanowires. The nanowire dispersion liquid is a 6-mg / ml nanowire ethanol dispersion liquid; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0048] Example 3: S1: Take an aluminum oxide ultra-thin porous nanoplate with a nanopore size of 200 nm and a 100-μm-thick copper metal foil. First, clean it with deionized water for 10 min, then clean it with isopropanol for 10 min, and finally clean it with ethanol for 10 min; cut it into square chips with a side length of 5 mm.

[0049] S2: Coat a solid lubricant on the aluminum oxide ultra-thin porous nanoplate, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device at a device frequency of 20 kHz to obtain an aluminum oxide ultra-thin porous nanoplate / substrate with copper metal rods of 200 nm in size.

[0050] S3: Immerse the aluminum oxide ultra-thin porous nanoplate / substrate stack obtained in step S2 in a 1M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed.

[0051] S4: Use nanolaser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires.

[0052] S5: Uniformly scrape a 1-μm-thick conductive adhesive on the surface of the polypropylene film, spray the nanowires. When spraying the nanowires, a nanowire dispersion is used, and the nanowire dispersion is a 6-mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure it under ultraviolet light at 120 °C for 5 min to obtain a current collector.

[0053] Example 4: S1: Take an aluminum oxide ultra-thin porous nanoplate with a nanopore size of 300 nm and a 100-μm-thick copper metal foil. First, clean it with deionized water for 10 min, then clean it with isopropanol for 10 min, and finally clean it with ethanol for 10 min; cut it into square chips with a side length of 5 mm.

[0054] S2: Coat a solid lubricant on the aluminum oxide ultra-thin porous nanoplate, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device at a device frequency of 20 kHz to obtain an aluminum oxide ultra-thin porous nanoplate / substrate with copper metal rods of 300 nm in size.

[0055] S3: Immerse the aluminum oxide ultra-thin porous nanoplate / substrate stack obtained in step S2 in a 1M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed.

[0056] S4: Use nanolaser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires.

[0057] S5: Uniformly scrape and coat a conductive adhesive with a thickness of 1 μm on the surface of the polypropylene film, and spray the nanowires. A nanowire dispersion is used when spraying the nanowires. The nanowire dispersion is a 6 mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0058] Example 5: S1: Take an alumina ultra-thin porous nanoplates with a nanopore size of 130 nm and a 100-μm-thick copper metal foil. First, wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm.

[0059] S2: Coat a solid lubricant on the alumina ultra-thin porous nanoplates, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device. The device frequency is 15 kHz to obtain an alumina ultra-thin porous nanoplates / substrate with copper metal rods with a size of 130 nm.

[0060] S3: Immerse the alumina ultra-thin porous nanoplates / substrate stack obtained in step S2 in 1 M NaOH solution for 2 h to obtain a metal substrate with exposed nanowires.

[0061] S4: Use nanolaser cutting technology to cut the nanowires on the metal substrate to obtain nanowires.

[0062] S5: Uniformly scrape and coat a conductive adhesive with a thickness of 1 μm on the surface of the polypropylene film, and spray the nanowires. A nanowire dispersion is used when spraying the nanowires. The nanowire dispersion is a 6 mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0063] Example 6: S1: Take an alumina ultra-thin porous nanoplates with a nanopore size of 130 nm and a 100-μm-thick copper metal foil. First, wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm.

[0064] S2: Coat a solid lubricant on the alumina ultra-thin porous nanoplates, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device. The device frequency is 25 kHz to obtain an alumina ultra-thin porous nanoplates / substrate with copper metal rods with a size of 130 nm.

[0065] S3: Immerse the alumina ultra-thin porous nanoplates / substrate stack obtained in step S2 into 1M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed;

[0066] S4: Use nanolaser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires;

[0067] S5: Uniformly scrape a conductive adhesive with a thickness of 1 μm on the surface of the polypropylene film, and spray nanowires. A nanowire dispersion is used when spraying the nanowires. The nanowire dispersion is a 6 mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0068] Example 7: S1: Take an alumina ultra-thin porous nanoplate with a nanopore size of 300 nm and a 100-μm-thick copper metal foil. First, wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm;

[0069] S2: Coat a solid lubricant in the alumina ultra-thin porous nanoplate, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device. The device frequency is 20 kHz to obtain an alumina ultra-thin porous nanoplate / substrate with copper metal rods with a size of 300 nm;

[0070] S3: Immerse the alumina ultra-thin porous nanoplates / substrate stack obtained in step S2 into 1M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed;

[0071] S4: Use nanolaser cutting technology to cut off the nanowires on the metal substrate to obtain nanowires;

[0072] S5: Take 16 parts of 2-hydroxyethyl methacrylate, 100 parts of polypropylene, and 1 part of benzoyl peroxide, heat to 210 °C, and react for 3 h to obtain an intermediate; take 100 parts of the intermediate, add it to 150 parts of N,N-dimethylformamide, stir evenly, add 2 parts of anhydrous sodium carbonate and 25 parts of bis(4-nitrophenyl) phosphate, heat to 185 °C under a nitrogen atmosphere, react for 12 h, and carry out vacuum reflux to obtain modified polypropylene;

[0073] The modified polypropylene is melt-extruded; after the obtained melt is formed into a sheet by a cooling roll and a high-pressure air knife, it is longitudinally stretched and then transversely stretched by a longitudinal stretching machine and a transverse stretching machine in sequence; the temperature of the cooling roll is 90 °C, the gas temperature of the high-pressure air knife is 60 °C, and the blowing speed is 150 m / s; the stretching temperature for longitudinal stretching is 150 °C, the setting temperature is 150 °C, preferably 150 °C, and the stretching ratio is 7; the stretching temperature for transverse stretching is 160 °C, the setting temperature is 175 °C, and the stretching ratio is 12; it is heat-insulated at 120 °C for 5 min and subjected to corona treatment; the corona power is 80 kW and the linear speed is 200 m / min; a modified polypropylene film is obtained;

[0074] S6: A conductive adhesive with a thickness of 1 μm is evenly scrape-coated on the surface of the modified polypropylene film, and nanowires are sprayed. A nanowire dispersion liquid is used when spraying the nanowires. The nanowire dispersion liquid is a 6 mg / ml nanowire ethanol dispersion liquid; the spraying speed is 15 mm / s; the atomizing pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, it is cured at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0075] Comparative Example 1 (not applicable to the nanoimprint process, using the conventional process of magnetron sputtering + water plating): The first step: A 100-nm copper layer is magnetron-sputtered on both sides of a 5-μm polypropylene film; the second step: A 1.5-μm copper layer is water-plated on the surface of the film body after magnetron sputtering to make a composite current collector.

[0076] Comparative Example 2 (the frequency of the ultrasonic imprinting equipment is changed to 10 kHz, and the other method steps are the same as those in Example 1): S1: Take an aluminum oxide ultra-thin porous nanoplate with a nanopore size of 130 nm and a 100-μm-thick copper metal foil. First, it is cleaned with deionized water for 10 min, then with isopropanol for 10 min, and finally with ethanol for 10 min; it is cut into square chips with a side length of 5 mm;

[0077] S2: A solid lubricant is coated in the aluminum oxide ultra-thin porous nanoplate, placed above the metal foil, and ultrasonic imprinting is carried out with a Branson2000X ultrasonic imprinting equipment at a frequency of 10 kHz to obtain an aluminum oxide ultra-thin porous nanoplate / substrate with copper metal rods with a size of 130 nm;

[0078] S3: The aluminum oxide ultra-thin porous nanoplate / substrate stack obtained in step S2 is immersed in a 1 M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed;

[0079] S4: The nanowires on the metal substrate are cut off by using a nano laser cutting technology to obtain nanowires;

[0080] S5: Uniformly scrape and coat a conductive adhesive with a thickness of 1 μm on the surface of the polypropylene film, and spray nanowires. A nanowire dispersion is used when spraying the nanowires. The nanowire dispersion is a 6 mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0081] Comparative Example 3 (changing the addition amounts of 2-hydroxyethyl methacrylate and bis(4-nitrophenyl) phosphate, and the remaining method steps are the same as those in Example 7): S1: Take an aluminum oxide ultra-thin porous nanoplate with a nanopore size of 300 nm and a 100-μm-thick copper metal foil. First, wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm.

[0082] S2: Coat a solid lubricant on the aluminum oxide ultra-thin porous nanoplate, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device. The device frequency is 20 kHz to obtain an aluminum oxide ultra-thin porous nanoplate / substrate with copper metal rods with a size of 300 nm.

[0083] S3: Immerse the aluminum oxide ultra-thin porous nanoplate / substrate stack obtained in step S2 in a 1 M NaOH solution for 2 h to obtain a metal substrate with exposed nanowires.

[0084] S4: Use a nanolaser cutting technique to cut the nanowires on the metal substrate to obtain nanowires.

[0085] S5: Take 25 parts of 2-hydroxyethyl methacrylate, 100 parts of polypropylene, and 1 part of benzoyl peroxide, mix and heat to 210 °C, and react for 3 h to obtain an intermediate; take 100 parts of the intermediate, add it to 150 parts of N,N-dimethylformamide, stir evenly, add 2 parts of anhydrous sodium carbonate and 35 parts of bis(4-nitrophenyl) phosphate, heat to 185 °C under a nitrogen atmosphere, react for 12 h, and carry out vacuum reflux to obtain modified polypropylene.

[0086] Melt-extrude the modified polypropylene; after the obtained melt is formed into a sheet by a cooling roll and a high-pressure air knife, successively perform longitudinal stretching and transverse stretching with a longitudinal stretching machine and a transverse stretching machine; the temperature of the cooling roll is 90 °C, the gas temperature of the high-pressure air knife is 60 °C, and the blowing speed is 150 m / s; the stretching temperature for longitudinal stretching is 150 °C, the setting temperature is 150 °C, preferably 150 °C, and the stretching ratio is 7; the stretching temperature for transverse stretching is 160 °C, the setting temperature is 175 °C, and the stretching ratio is 12; keep warm at 120 °C for 5 min and perform corona treatment; the corona power is 80 kW and the linear speed is 200 m / min; obtain a modified polypropylene film.

[0087] S6: Uniformly scrape and coat a conductive adhesive with a thickness of 1 μm on the surface of the modified polypropylene film, and spray nanowires. A nanowire dispersion is used when spraying the nanowires. The nanowire dispersion is a 6 mg / ml nanowire ethanol dispersion; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying, cure at ultraviolet light and 120 °C for 5 min to obtain a current collector.

[0088] Comparative Example 4 (using polypropylene with a melt index of 3 g / 10 min, and the rest of the method steps are the same as in Example 7): S1: Take an aluminum oxide ultra-thin porous nanoplank with a nanopore size of 300 nm and a 100-μm-thick copper metal foil. First, wash with deionized water for 10 min, then wash with isopropanol for 10 min, and finally wash with ethanol for 10 min; cut into square chips with a side length of 5 mm;

[0089] S2: Coat a solid lubricant in the aluminum oxide ultra-thin porous nanoplank, place it above the metal foil, and perform ultrasonic imprinting with a Branson 2000X ultrasonic imprinting device. The device frequency is 20 kHz to obtain an aluminum oxide ultra-thin porous nanoplank / substrate with copper metal rods sized 300 nm;

[0090] S3: Immerse the aluminum oxide ultra-thin porous nanoplank / substrate stack obtained in step S2 in a 1 M NaOH solution for 2 h to obtain a metal substrate with exposed nanowires;

[0091] S4: Use a nanolaser cutting technique to cut the nanowires on the metal substrate to obtain nanowires;

[0092] S5: Take 16 parts of 2-hydroxyethyl methacrylate, 100 parts of polypropylene, and 1 part of benzoyl peroxide, mix and heat to 210 °C, react for 3 h to obtain an intermediate; take 100 parts of the intermediate, add it to 150 parts of N,N-dimethylformamide, stir evenly, add 2 parts of anhydrous sodium carbonate and 25 parts of bis(4-nitrophenyl) phosphate, heat to 185 °C under a nitrogen atmosphere, react for 12 h, and carry out reduced-pressure reflux to obtain modified polypropylene;

[0093] Melt-extrude the modified polypropylene; after the obtained melt is formed into a sheet by a cooling roll and a high-pressure air knife, then perform longitudinal stretching and transverse stretching by a longitudinal stretching machine and a transverse stretching machine in sequence; the temperature of the cooling roll is 90 °C, the gas temperature of the high-pressure air knife is 60 °C, and the blowing speed is 150 m / s; the stretching temperature for longitudinal stretching is 150 °C, the setting temperature is 150 °C, preferably 150 °C, and the stretching ratio is 7; the stretching temperature for transverse stretching is 160 °C, the setting temperature is 175 °C, and the stretching ratio is 12; keep warm at 120 °C for 5 min and perform corona treatment; the corona power is 80 kW and the linear speed is 200 m / min; obtain a modified polypropylene film;

[0094] S6: Uniformly scrape and coat the surface of the modified polypropylene film with a conductive adhesive having a thickness of 1 μm, and spray nanowires. A nanowire dispersion is used when spraying the nanowires. The nanowire dispersion is a 6 mg / ml ethanol dispersion of nanowires; the spraying speed is 15 mm / s; the atomization pressure is 20 MPa; the nozzle diameter is 100 μm; after spraying is completed, cure it under ultraviolet light and at 120 °C for 5 min to obtain a current collector.

[0095] In the above examples, unless otherwise specified, the test methods used are all conventional methods; unless otherwise specified, the raw materials used can all be obtained from commercial channels, and the raw material sources are as follows: ultra-thin porous alumina nanoplates (commercially available anodic aluminum oxide AAO templates); solid lubricants (C60); conductive adhesives (LOCTITE ABLESTIK ICP 3850); 2-hydroxyethyl methacrylate (S24381, Yuanye, Shanghai); benzoyl peroxide (CAS: 94-36-0); N,N-dimethylformamide (CAS: 68-12-2); anhydrous sodium carbonate (S24152, Yuanye, Shanghai); bis(4-nitrophenyl) phosphate (S30868, Yuanye, Shanghai); ethanol (CAS: 64-17-5).

[0096] Experiment: Take the current collectors prepared in Examples 1 to 7 and Comparative Examples 1 to 4, and refer to ASTM B533: Standard Test Method for Peel Strength of Metal Electroplated Plastics of the American Society for Testing and Materials to test the coating peel force; specifically as follows: Use a universal testing machine to cut a specimen with a width of (25.0 ± 0.25) mm from the composite current collector material, install the prepared specimen on the fixture of the testing equipment, the peel angle is 90°, the test speed is 100 mm / min, divide the peel force by the width of the specimen to obtain the peel force per unit width (N / m); the specific data are shown in the following table;

[0097]

[0098] Conclusion: The current collector layer prepared by the present invention by ultrasonic imprinting to prepare nanowires and spraying them on the surface of a polymer film has good bonding strength between layers, can significantly improve the safety performance of the battery, and increase the cycle life of the battery. From Example 7, when the polymer film is a modified polypropylene film, due to the improvement of mechanical properties and crystallinity, the peel force is further enhanced; from Comparative Example 3, it can be seen that the addition amount of 2-hydroxyethyl methacrylate grafted on the side chain needs to be controlled, otherwise it will instead lead to a decrease in performance; from Comparative Example 4, the selection of polypropylene also has an important influence; in summary, the modified polypropylene film prepared by the present invention has good surface adhesion performance, good storage stability, good mechanical properties, and good peel strength of the prepared current collector.

[0099] Finally, it should be noted that the above are only the preferred embodiments of the present invention, but the protection scope of this application is not limited thereto. Any changes or substitutions that can be easily thought of by those skilled in the art within the technical scope disclosed in this application, within the spirit and principle of the present invention, should be covered by the protection scope of this application; without conflict, the implementation manners of this application and the features in the implementation manners can be combined with each other. Therefore, the protection scope of this application should be subject to the protection scope of the claims.

Claims

1. A method for preparing a current collector with high binding force, characterized in that: The following steps are involved: S1: Take the alumina porous nanoplate and metal foil, wash them, and cut them into square chips with a side length of 1-5 mm; S2: evenly coating the alumina porous nanoplate with solid lubricant, placing it on top of the metal foil, and performing ultrasonic embossing using an ultrasonic embossing device with a frequency of 15-25kHz to obtain an alumina porous nanoplate / substrate with a metal rod; S3: immersing the alumina porous nanoplate / substrate stack obtained in step S2 in a 1M NaOH solution for 2 h to obtain a metal substrate with nanowires exposed; S4: using nano laser cutting technology to cut away the nanowires on the metal substrate to obtain nanowires; S5: Evenly apply conductive glue on the surface of the polymer film, control the surface temperature to 70°C, and spray nanowires; A nanowire dispersion is used when spraying the nanowires, wherein the nanowire dispersion is a 2-10 mg / ml nanowire ethanol dispersion; Injection speed 10~20mm / s; Atomization pressure is 5~30MPa; nozzle diameter is 50~200μm; After the spraying is completed, the current collector is cured for 5 minutes under the conditions of UV intensity of 50~200mW / cm² and temperature of 110~120℃; The metal foil is a copper metal foil with a thickness of 100 μm; the thickness of the alumina porous nanoplate is 500-800 nm, and the size of the nanopores is 100-300 nm.

2. The method for preparing a current collector with high binding force according to claim 1, characterized in that: The solid lubricant is carbon 60, and the coating thickness is 80-120 nm.

3. The method for preparing a current collector with high binding force according to claim 1, characterized in that: The polymer film is a BOPP polypropylene film with a thickness of 4 to 10 μm.

4. The method for preparing a current collector with high binding force according to claim 1, characterized in that: The thickness of the conductive adhesive is 0.8-1 μm.

5. The method for preparing a current collector with high binding force according to claim 3, characterized in that: The polymer film is a modified polypropylene film, and the specific preparation method is The following steps are involved: S1: Mix hydroxyethyl methacrylate, polypropylene and benzoyl peroxide, heat to 200-210°C, react for 2-3 hours to obtain an intermediate; take the intermediate, add it to N,N-dimethylformamide, stir evenly, add anhydrous sodium carbonate and bis(4-nitrophenyl) phosphate, heat to 180-190°C under nitrogen atmosphere, react for 10-12 hours, and reflux under reduced pressure to obtain modified polypropylene; S2: Melting and extruding the modified polypropylene; The obtained melt casting sheet is formed, and longitudinal stretching and transverse stretching, heat preservation and corona treatment are performed in sequence to obtain a modified polypropylene film.

6. The method for preparing a current collector with high binding force according to claim 5, characterized in that: The intermediate comprises the following raw materials, calculated by weight: 15-20 parts of hydroxyethyl methacrylate, 100 parts of polypropylene, and 1-2 parts of benzoyl peroxide; The modified polypropylene comprises the following raw materials, calculated by mass: 100 parts of an intermediate, 150-180 parts of N,N-dimethylformamide, 1-2 parts of anhydrous sodium carbonate, and 25-30 parts of bis(4-nitrophenyl)phosphate.

7. A current collector prepared according to the method for preparing a current collector with high binding force according to any one of claims 1 to 6.

8. A battery, characterized in that: Comprising the current collector as claimed in claim 7.

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