Single-walled carbon nanotube thin film battery current collector and preparation method thereof

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a single-walled carbon nanotube thin film battery current collector and a preparation method thereof.The preparation method comprises the following steps that S1, carbon black powder is subjected to acid treatment with concentrated nitric acid, and the carbon black powder and the concentrated nitric acid are taken to form mixed carbon black powder; s2, graphene-nano silver composite powder is prepared; s3, taking products in S1 and S2 and single-walled carbon nanotube powder, adding the products and the single-walled carbon nanotube powder into the dispersion liquid, and stirring to form mixed liquid; and S4, preparing the precursor into a composite film by using a spraying method, and carrying out gradient heating drying and annealing on the composite film to obtain the composite single-walled carbon nano-film. S5, stripping the composite single-walled carbon nano-film from the plastic substrate and rolling the composite single-walled carbon nano-film; and S6, shearing the composite single-walled carbon nano-film to obtain the composite single-walled carbon nano-film. The single-walled carbon nanotube thin film battery current collector obtained in the invention has the advantages of light weight, high flexibility and high energy density.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of batteries, and particularly relates to a single-walled carbon nanotube film battery current collector and a preparation method thereof. BACKGROUND

[0002] At present, the current collector for lithium electronic batteries is mostly aluminum or copper foil. However, the aluminum or copper foil as the current collector does not contribute to the capacity of the battery, and the mass of the aluminum or copper foil accounts for about 15% of the entire positive electrode and about 50% of the negative electrode, which seriously restricts the energy density of the battery. Therefore, using a conductive material with lower density to replace the aluminum or copper foil as the current collector is an effective way to improve the energy density of the battery.

[0003] Carbon nanotubes are a new type of one-dimensional nanomaterial, and the unique graphitization structure thereof makes it have excellent electrical properties. Compared with metals, the density of the carbon nanotube is extremely low. These characteristics make the carbon nanotube film formed by the carbon nanotube expected to replace the aluminum or copper foil to become a new generation of lithium ion battery current collector.

[0004] The conductive path in the macro single-walled carbon nanotube film is a random network, and a concentration of more than 80wt% of SWCNT is required to form a continuous path. However, high concentration causes serious agglomeration, which reduces the effective conductivity. The tube bundles in the macro single-walled carbon nanotube film are in contact depending on the van der Waals force, and the electron transmission needs to cross the energy barrier, resulting in high resistivity. The mechanical properties of the macro single-walled carbon nanotube film are fragile, which cannot withstand the stress of battery assembly. The above defects make the macro single-walled carbon nanotube film unable to be directly used as a battery current collector. In the prior art, in order to enhance the carrier capacity of the carbon nanotube film to improve the effective conductivity and fill the pores in the carbon nanotube film to improve the mechanical properties, a layer of copper or aluminum is PVD sputtered on the purified and dried carbon nanotube film. Compared with the traditional metal current collector, the mass is effectively reduced, the activity density of the battery is improved, and compared with the macro single-walled carbon nanotube film, the conductivity and mechanical properties are effectively improved, which is a better choice for the current collector of a lightweight battery.

[0005] However, the sputtered metal layer on the pure carbon nanotube film not only relieves the inherent defects but also introduces new problems. The mass ratio of the sputtered metal layer is too high, the density of the metal is incompressible, and the lightweight characteristics of the carbon nanotube are offset, so that the current collector obtained by the technical solution cannot meet the demand of a lightweight battery. The metal is easily oxidized to form an insulating oxide in a temperature rising environment, which directly affects the conductivity of the current collector. The carbon nanotube film with the sputtered metal layer improves the rigidity, but correspondingly reduces the flexibility, so that it is difficult to be applied to a flexible battery.

[0006] Therefore, it is necessary to develop a new battery current collector material which meets the conductivity requirement of the battery current collector while improving the energy density and flexibility, so that it can be applied to a flexible and ultralight new battery. SUMMARY

[0007] The present application aims to provide a single-walled carbon nanotube thin film battery current collector and a preparation method thereof to solve the above technical problems.

[0008] To achieve the above technical purposes, the technical scheme of the present application is as follows: A preparation method of a single-walled carbon nanotube thin film battery current collector comprises the following steps: S1: carbon black powder is subjected to acid treatment using concentrated nitric acid to obtain modified carbon black powder, and the carbon black powder and the modified carbon black powder are taken in a mass ratio of 4:1 to form mixed carbon black powder; S2: acetylacetone silver and graphene oxide are reduced in the same system to generate graphene-nano silver composite powder; S3: the mixed carbon black powder, the graphene-nano silver composite powder and single-walled carbon nanotube powder are taken and added to a dispersion liquid to form a mixed liquid, wherein the mass ratio of the graphene-nano silver composite powder to the mixed carbon black powder is 1:50, and the mass ratio of the single-walled carbon nanotube powder to the mixed carbon black powder is 9:1, the temperature of the mixed liquid is raised to 40℃ and then gradiently raised to prepare a precursor liquid; S4: the precursor liquid is sprayed on a plastic substrate to form a composite thin film, and the composite thin film is gradiently dried and annealed to obtain a composite single-walled carbon nanotube thin film; S5: the composite single-walled carbon nanotube thin film is peeled off from the plastic substrate, rolled up and cut to obtain a single-walled carbon nanotube thin film battery current collector.

[0009] As a further improvement, in step S1, the specific process of the acid treatment is as follows: carbon black powder is weighed, 65-68% concentrated nitric acid is added to the carbon black powder at a drop rate of 5-10 mL / min, the solid-liquid ratio of the carbon black powder to the concentrated nitric acid is 0.1 g:1 mL, stirring is performed at 100-500 rpm, water bath heating is performed to raise the temperature to 80-90℃, condensation reflux is performed, the reaction is performed for 6-10 h, heating is stopped after the reaction is completed, stirring is continued until the reaction liquid is cooled to room temperature, deionized water is added to the reaction liquid, the amount of the deionized water added is 10-20 times the volume of the reaction liquid, suction filtration is performed, the filter cake is washed with deionized water for 6-8 times, and drying is performed to make the modified carbon black powder close to neutral, thereby obtaining the modified carbon black powder.

[0010] As a further improvement, in step S2, the specific process of the reduction is as follows: mixing oleylamine and dibenzyl ether at a volume ratio of 1:2, stirring uniformly to prepare a mixed solvent, adding the mixed solvent into graphene oxide, heating to 30 DEG C in a water bath, adding silver acetylacetonate, reacting for 2-3 h, adding 2 mol / L lithium borohydride tetrahydrofuran solution, continuing to react for 0.5-1 h, wherein the mass ratio of silver acetylacetonate to graphene oxide is 1.3:1, and the ratio of silver acetylacetonate to lithium borohydride tetrahydrofuran solution is 0.017 g:1 mL, after the reaction is completed, filtering to obtain a solid product, washing the solid product with 50-75% ethanol, using 50-75% ethanol in an amount of 100-150 times the volume of the mixed solvent, centrifuging, taking the precipitate, and vacuum drying at room temperature to obtain a graphene-nano silver composite powder.

[0011] As a further improvement, in step S3, the preparation process of the mixed solution is as follows: mixing N-methylpyrrolidone and tetrahydrofuran at a volume ratio of 4:1, stirring uniformly to prepare a dispersion liquid, putting the mixed carbon black powder and the graphene-nano silver composite powder into a reaction container, adding the dispersion liquid into the reaction container, stirring at 30-40 DEG C, and adding single-walled carbon nanotube powder while stirring to form a mixed solution.

[0012] As a further improvement, in step S3, the process of the gradient temperature rise is as follows: First stage: normal pressure, rising the temperature of the mixed solution from 40 DEG C to 60 DEG C at a rate of 1 DEG C / min, and stirring at 100-200 rpm; Second stage: negative pressure-0.05 MPa, rising the temperature of the mixed solution from 60 DEG C to 80 DEG C at a rate of 1 DEG C / min, and stirring at 100-200 rpm; Third stage: negative pressure-0.09 MPa, rising the temperature of the mixed solution from 80 DEG C to 110 DEG C at a rate of 0.5 DEG C / min.

[0013] As a further improvement, in step S4, the specific process of the spraying is as follows: washing and drying a plastic substrate, activating the surface of the plastic substrate by using 50W oxygen plasma for 2-5 min; controlling the temperature of the plastic substrate at 60-80 DEG C, delivering a precursor liquid by a precise constant-flow liquid supply system, spraying the precursor liquid onto the plastic substrate by an ultrasonic spraying system, introducing argon as a carrier gas for protection, controlling the spraying distance at 10-20 cm, the flow rate at 0.1-1 mL / min, the carrier gas pressure at 0.1-0.3 MPa, and the spraying thickness at 20-25 um.

[0014] As a further improvement, in step S4, the specific process of the gradient temperature rise drying is as follows: First stage: placed in 25℃, 80% humidity environment for 20min; Second stage: placed in 40℃, 50% humidity environment for 30min; Third stage: placed in 60℃, 20% humidity environment for 15min.

[0015] As a further improvement, in step S4, the specific process of the annealing is that the composite film is heat treated at 200~300℃ for 0.5~1h under argon protection, to obtain a composite single-walled carbon nanotube film.

[0016] As a further improvement, the operation of step 5 is that the mechanical peeling adopts a peeling angle of 15-30°, and the peeling is carried out at a uniform speed of 90-110m / min, with the tension controlled at 0.002-0.005 kN / m; the winding speed is 30-120 m / min, and the spraying thickness is 20~25um.

[0017] The application also provides a single-walled carbon nanotube film battery current collector prepared by the above preparation method, which is prepared based on the above method, contains about 90wt% of single-walled carbon nanotubes, about 10wt% of carbon black, and about 0.1~0.5wt% of graphene-nano silver, wherein the carbon black with oxygen-containing functional groups accounts for 5~10wt% of the total amount of carbon black.

[0018] Due to the adoption of the above technical solutions, the application has the following beneficial effects: strong acid is introduced as a strong oxidizing agent to introduce oxygen-containing functional groups, improve the polarity of the reaction system, improve the dispersibility of carbon black and single-walled carbon nanotubes in the preparation of the precursor solution, reduce the agglomeration degree of effective single-walled carbon nanotubes, make the distribution of carbon black and single-walled carbon nanotubes more uniform, and improve the conductivity of the final product. The oxygen-containing functional groups in the modified carbon black powder can improve the viscosity between the molecules in the final composite single-walled carbon nanotube film, while reducing the agglomeration of single-walled carbon nanotubes, improving the mechanical properties, and improving the conductivity on the macro level.

[0019] The nano silver is dispersed in the carbon molecules to establish a "metal electronic bridge" to make up for the part of the conductivity sacrificed by the introduction of oxygen-containing functional groups; the graphene-nano silver is compounded, and the oxidation sensitivity of the nano silver is significantly reduced by the carrier protection of the graphene, so that the comprehensive stability of the nano silver is higher than that of silver element, the oxidation speed of the nano silver in the use of the current collector is reduced, and the service life of the product current collector is prolonged.

[0020] The annealing process removes the residual solvent in the composite film, removes part of the oxygen-containing functional groups, so that the carbon black with oxygen-containing functional groups in the film accounts for less than 10wt% of the total amount of carbon black, and improves the conductivity of the final product.

[0021] The obtained single-walled carbon nanotube film battery current collector has the advantages of light weight, high flexibility and high energy density, and the conductivity can meet the requirements of the battery current collector, and can be applied to flexible and ultra-light new type batteries. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 is a 20-micron characterization map of the single-walled carbon nanotube film sample of the present application; Figure 2 is a 5-micron characterization map of the single-walled carbon nanotube film sample of the present application; Figure 3 is a 100-nanometer characterization map of the single-walled carbon nanotube film sample of the present application. DETAILED DESCRIPTION

[0023] The technical solutions of the present application will be described clearly and completely in combination with the specific embodiments below, but those skilled in the art will understand that the following described embodiments are part of the embodiments of the present application, not all the embodiments, and are only used to illustrate the present application, and should not be regarded as limiting the scope of the present application. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application. The specific conditions are not specified in the embodiments, and are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are conventional products that can be purchased on the market.

[0024] S1: The carbon black powder is acid treated with concentrated nitric acid to obtain a modified carbon black powder.

[0025] A carbon black powder accounting for 20wt% of the total carbon black is weighed into a reaction vessel, 65-68% concentrated nitric acid is weighed according to a solid-liquid ratio of 1:10, the concentrated nitric acid is slowly added to the reaction vessel containing the carbon black powder at a rate of 5-10mL / min, and low-speed stirring is performed at 100-500rpm to prevent splashing; water bath heating is performed to heat to 80-90℃, and condensation reflux is performed, and the reaction is carried out for 6-10h to make the reaction sufficient and introduce sufficient oxygen-containing functional groups; after the reaction is completed, the heating is stopped, and the stirring is continued until the system is cooled to room temperature, more than ten times the volume of deionized water is added to the reaction system, and the filter cake is repeatedly washed for 6-8 times. The modified carbon black powder is close to neutral; the carbon black powder and the modified carbon black powder are taken according to a mass ratio of 4:1 to form a mixed carbon black powder.

[0026] S2: Acetylacetone silver and graphene oxide are reduced in the same system to generate a graphene-nano silver composite powder.

[0027] Mixing the oleylamine and dibenzyl ether in a ratio of 1:2, stirring to make a mixed solvent, putting the graphene oxide into a reaction vessel, adding the mixed solvent into the reaction vessel, heating to 30℃ in a water bath, adding silver acetylacetonate, reacting for 2-3h, adding a reducing agent of 2mol / L lithium borohydride tetrahydrofuran solution to continue reacting for 0.5-1h, wherein the mass ratio of silver acetylacetonate to graphene oxide is 1.3:1, the mass ratio of silver acetylacetonate to lithium borohydride tetrahydrofuran solution is 17g / L, and the mass ratio of silver acetylacetonate to mixed solvent is 43g / L, after the reaction, filtering to obtain a solid product, washing the solid product with 50-75% ethanol, the amount of 50-75% ethanol added is 100-150 times the volume of the mixed solvent, centrifuging, taking the precipitate, and vacuum drying the sample at room temperature to obtain a graphene-nano silver composite powder.

[0028] S3: taking the mixed carbon black powder, graphene-nano silver composite powder and single-walled carbon nanotube powder, adding them into a dispersion liquid to form a mixed liquid, wherein the mass ratio of graphene-nano silver composite powder to mixed carbon black powder is 1:50, and the mass ratio of single-walled carbon nanotube powder to mixed carbon black powder is 9:1, and then increasing the temperature of the mixed liquid to 40℃ and then increasing the temperature in stages to prepare a precursor liquid.

[0029] Mixing N-methylpyrrolidone and tetrahydrofuran in a volume ratio of 4:1, stirring to make a dispersion liquid, putting the mixed carbon black powder and graphene-nano silver composite powder into a reaction vessel, adding the dispersion liquid into the reaction vessel, stirring at 30-40℃, and adding the single-walled carbon nanotube powder while stirring to form a mixed liquid.

[0030] Gradient temperature increase: first stage: atmospheric pressure, increasing the temperature of the mixed liquid from 40℃ to 60℃ at a rate of 2℃ / min, and stirring at 200-300rpm; Second stage: negative pressure-0.05MPa, increasing the temperature of the mixed liquid from 60℃ to 80℃ at a rate of 1℃ / min, and stirring at 100-200rpm; Third stage: negative pressure-0.09MPa, increasing the temperature of the mixed liquid from 80℃ to 110℃ at a rate of 0.5℃ / min.

[0031] S4: spraying the precursor liquid on a plastic substrate to form a composite thin film, and drying and annealing the composite thin film to obtain a composite single-walled carbon nanometer thin film; Clean and dry the plastic substrate. Activate the surface of the plastic substrate by treating it with 50W oxygen plasma for 2-5 minutes to enhance adhesion. Control the temperature of the plastic substrate at 60-80℃. Deliver the precursor solution through a precision constant flow liquid supply system. Spray the precursor solution onto the plastic substrate using an ultrasonic spraying system. Introduce argon as a carrier gas for protection. The spraying distance is 10-20cm, the flow rate is controlled at 0.1-1mL / min, the carrier gas pressure is 0.1-0.3MPa, and the spraying thickness is 20-25µm.

[0032] Gradient drying: First stage: Place at 25℃ and 80% humidity for 20 minutes; Second stage: Curing at 40℃ and 50% humidity for 30 minutes; Third stage: final drying at 60℃ and 20% humidity for 15 minutes.

[0033] The obtained composite film was annealed at 200~300℃ for 0.5~1h under argon protection to obtain a composite single-walled carbon nanotube film.

[0034] S5: Peel and wind the composite single-walled carbon nanofilm from the plastic substrate. Mechanical peeling is performed at a peeling angle of 15-30°, at a uniform peeling speed of 0.06~0.12m / min, with tension controlled at 0.002~0.005kN / m.

[0035] S6: The composite single-walled carbon nanotube thin film is sheared to obtain the single-walled carbon nanotube thin film battery current collector.

[0036] In S1, the strong acid acts as a strong oxidizing agent, attacking defect sites, edges, or sps on the carbon black surface. 2 Hybridized carbon atoms undergo oxidation reactions, oxidizing some carbon atoms on the surface of carbon black to generate functional groups such as carboxyl groups (-COOH), hydroxyl groups (-OH), and carbonyl groups (C=O). These oxygen-containing functional groups increase the polarity of the reaction system, improve the dispersibility of carbon black and single-walled carbon nanotubes in the preparation of precursor solutions, reduce the agglomeration degree of effective single-walled carbon nanotubes, make the distribution of carbon black and single-walled carbon nanotubes more uniform, and improve the conductivity of the final product.

[0037] In S2, graphene and silver nanoparticles are combined. The graphene carrier significantly reduces the oxidation sensitivity of silver nanoparticles, making its overall stability higher than that of elemental silver. This reduces the rate at which silver nanoparticles are oxidized during the use of the current collector, thus extending the service life of the current collector.

[0038] In S3, the oxygen-containing functional groups in the modified carbon black powder can increase the viscosity between the molecules in the final composite single-walled carbon nanotube film, while reducing the agglomeration of the single-walled carbon nanotubes, improving the mechanical properties and the conductivity at the macro level. Graphene-nano silver can assist in building a conductive network in the composite single-walled carbon nanotube film, compensating for the reduction in conductivity caused by the introduction of oxygen-containing functional groups.

[0039] In S4, the annealing process removes the residual solvent in the composite film, removes part of the oxygen-containing functional groups, so that the oxygen-containing functional group-containing carbon black in the film accounts for less than 10wt% of the total carbon black, and improves the conductivity of the final product.

[0040] The single-walled carbon nanotube film battery current collector obtained has a single-walled carbon nanotube content of about 90wt%, a carbon black content of about 10wt%, and an oxygen-containing functional group-containing carbon black accounting for 5-10wt% of the total carbon black, and a graphene-nano silver content of about 0.1-0.5wt%. The sample characterization chart is shown in Figure 1 .

[0041] The technical solutions provided by the present application are described in detail below through examples and comparative examples. Example 1

[0042] 1. Take 0.2g of carbon black powder in a reaction container, measure 20mL of 68% concentrated nitric acid, and add the concentrated nitric acid to the reaction container containing the carbon black powder at a rate of 5mL / min, and stir at a low speed of 100rpm to prevent splashing; water bath heating, heating to 90℃, condensation reflux, reaction for 6h; after the reaction is completed, stop heating, continue stirring until the system cools to room temperature, add deionized water with a volume of more than ten times to the reaction system, and filter, and wash the filter cake repeatedly for 6 times.

[0043] 2. Mix 0.2mL of oleylamine with 0.4mL of dibenzyl ether to prepare a mixed solution one, put 20mg of graphene oxide into a reaction container, add the mixed solution one to the reaction container, heat the water bath to 30℃, add 26mg of silver acetylacetone, react for 2h, add 1.53mL of 2mol / L lithium borohydride tetrahydrofuran reducing agent, and continue to react for 0.5h, centrifuge the obtained product with ethanol and water, and vacuum dry the sample at room temperature to obtain graphene-nano silver composite powder.

[0044] 3. Mix 32mL of N-methylpyrrolidone with 8mL of tetrahydrofuran to prepare a mixed solution two, put the modified carbon black powder obtained in step 1 and 0.8g of unmodified carbon black powder into a reaction container, put the graphene-nano silver composite powder obtained in step 2 into the reaction container, and add the mixed solution two to the reaction container, and stir at a temperature of 30℃, and add 9g of single-walled carbon nanotubes to form a stable solution.

[0045] Gradient temperature rising: the first stage, normal pressure temperature rising, temperature range 40~60℃, temperature rising rate 2℃ / min, 200rpm stirring, condensing recovery of evaporated gas; the second stage, negative pressure-0.05MPa temperature rising, temperature range 60~80℃, temperature rising rate 1℃ / min, 100rpm stirring, condensing recovery of evaporated gas; the third stage, negative pressure-0.09MPa temperature rising, temperature range 80~110℃, temperature rising rate 0.5℃ / min, condensing recovery of evaporated gas to get precursor solution.

[0046] 4, 5x5cm plastic substrate was washed and dried, the surface of the plastic substrate was activated by oxygen plasma with power of 50W for 2min, the temperature of the plastic substrate was controlled at 60℃, the precursor solution was delivered by precision constant flow liquid supply system, the precursor solution was sprayed onto the plastic substrate by ultrasonic spraying system, argon gas was introduced as carrier gas, spraying distance: 10cm, flow control: 0.1mL / min, carrier gas pressure: 0.1MPa, spraying thickness: 20um.

[0047] Gradient drying: the first stage, 20min, 25℃, 80% humidity; the second stage, 30min, 40℃, 50%; the third stage, 15min, 60℃, 20% humidity, to get composite film.

[0048] The obtained composite film was annealed at 200℃ for 0.5h under argon protection to get composite single-walled carbon nanotube film.

[0049] 5, the composite single-walled carbon nanotube film was peeled off from the plastic substrate and rolled up, the mechanical peeling used 30° peeling angle, and the micro winding machine peeled off at a speed of 90m / min. Example 2

[0050] 1, weigh 1g of carbon black powder in a reaction container, measure 100mL of 65% concentrated nitric acid, add the concentrated nitric acid into the reaction container containing the carbon black powder at a rate of 5mL / min, stir at 300rpm to prevent splashing; water bath heating, temperature rising to 80℃, condensation reflux, reaction for 8h; after the reaction is completed, stop heating, continue stirring until the system cools to room temperature, add deionized water with a volume more than ten times to the reaction system, and filter, and the filter cake is washed repeatedly for 8 times.

[0051] 2. Mix 1 mL of oleylamine with 2 mL of dibenzyl ether, stir to make a mixed solution one, put 100 mg of graphene oxide into a reaction vessel, add the mixed solution one into the reaction vessel, heat to 30°C in a water bath, add 130 mg of silver acetylacetonate, react for 3 h, add 7.65 mL of 2 mol / L lithium borohydride tetrahydrofuran solution as a reducing agent, continue to react for 1 h, centrifugal wash the obtained product with ethanol and water, vacuum dry the sample at room temperature, and graphene-nano silver composite powder is obtained.

[0052] 3. Mix 160 mL of N-methylpyrrolidone with 40 mL of tetrahydrofuran, stir to make a mixed solution two, put the modified carbon black powder obtained in step 1 and 4 g of unmodified carbon black powder into a reaction vessel, put the graphene-nano silver composite powder obtained in step 2 into the reaction vessel, add the mixed solution two into the reaction vessel, stir at 30°C, and add 45 g of single-walled carbon nanotubes to form a stable solution.

[0053] Gradient temperature rising: first stage, normal pressure temperature rising, temperature range 40-60°C, temperature rising rate 2°C / min, 200 rpm stirring, condensation recovery of evaporated gas; second stage, negative pressure-0.05 MPa temperature rising, temperature range 60-80°C, temperature rising rate 1°C / min, 100 rpm stirring, condensation recovery of evaporated gas; third stage, negative pressure-0.09 MPa temperature rising, temperature range 80-110°C, temperature rising rate 0.5°C / min, condensation recovery of evaporated gas to obtain a precursor solution.

[0054] 4. Wash and dry a 10x10 cm plastic substrate, activate the surface of the plastic substrate by oxygen plasma treatment at a power of 50 W for 3 min, control the temperature of the plastic substrate at 70°C, deliver the precursor solution by a precision constant flow liquid supply system, spray the precursor solution onto the plastic substrate by an ultrasonic spraying system, introduce argon as a carrier gas, spraying distance: 10 cm, flow control: 0.5 mL / min, carrier gas pressure: 0.1 MPa, spraying thickness: 20 um.

[0055] Gradient drying: first stage, 20 min, 25°C, 80% humidity; second stage, 30 min, 40°C, 50%; third stage, 15 min, 60°C, 20% humidity, to obtain a composite film.

[0056] Anneal the obtained composite film at 250°C for 1 h under argon protection to obtain a composite single-walled carbon nanotube film.

[0057] 5. Peel and roll the composite single-walled carbon nanotube film from the plastic substrate, use a 30° peeling angle for mechanical peeling, and control the tension of an industrial grade winding machine at 0.004 kN / m for peeling. Example 3

[0058] 1. Take 4g of carbon black powder in a reaction vessel, measure 400mL of 65% concentrated nitric acid, add the concentrated nitric acid to the reaction vessel containing the carbon black powder at a rate of 10mL / min, stir at low speed of 500rpm to prevent splashing; heat with water bath, raise the temperature to 80℃, condense reflux, react for 10h; stop heating after the reaction is completed, continue stirring until the system cools to room temperature, add deionized water with a volume of more than ten times to the reaction system, and filter, wash the filter cake repeatedly 8 times.

[0059] 2. Mix 4mL of oleylamine with 8mL of dibenzy ether to make a mixed solution one, put 400mg of graphene oxide into a reaction vessel, add the mixed solution one to the reaction vessel, heat with water bath to 30℃, add 520mg of silver acetylacetone, react for 3h, add 30.6mL of 2mol / L boron hydride lithium tetrahydrofuran solution as a reducing agent to continue the reaction for 1h, centrifuge the obtained product with ethanol and water, vacuum dry the sample at room temperature, and obtain graphene-nano silver composite powder.

[0060] 3. Mix 640mL of N-methyl pyrrolidone with 160mL of tetrahydrofuran to make a mixed solution two, put the modified carbon black powder obtained in step 1 and 16g of unmodified carbon black powder into a reaction vessel, put the graphene-nano silver composite powder obtained in step 2 into the reaction vessel, add the mixed solution two to the reaction vessel, stir at a temperature of 40℃, and add 180g of single-walled carbon nanotubes to form a stable solution.

[0061] Gradient temperature rise: first stage, normal pressure temperature rise, temperature range 40~60℃, temperature rise rate 2℃ / min, 200rpm stirring, condensation recovery of evaporated gas; second stage, negative pressure-0.05MPa temperature rise, temperature range 60~80℃, temperature rise rate 1℃ / min, 100rpm stirring, condensation recovery of evaporated gas; third stage, negative pressure-0.09MPa temperature rise, temperature range 80~110℃, temperature rise rate 0.5℃ / min, condensation recovery of evaporated gas to obtain a precursor solution.

[0062] 4. Wash and dry a 30x30cm plastic substrate, activate the surface of the plastic substrate by oxygen plasma treatment at a power of 50W for 5min, control the temperature of the plastic substrate at 80℃, deliver the precursor solution by a precision constant flow liquid supply system, spray the precursor solution onto the plastic substrate by an ultrasonic spraying system, protect by argon gas, spraying distance: 20cm, flow control: 1mL / min, carrier gas pressure: 0.3MPa, spraying thickness: 25um.

[0063] Gradient drying: first stage, 20 min, 25℃, 80% humidity; second stage, 30 min, 40℃, 50%; third stage, 15 min, 60℃, 20% humidity, to obtain the composite film.

[0064] The obtained composite film was annealed at 300℃ for 1h under argon protection to obtain the composite single-walled carbon nanotube film.

[0065] 5. The composite single-walled carbon nanotube film was peeled off from the plastic substrate and rolled up, a peeling and rolling integrated machine was used, the peeling angle was set to 20°, the peeling speed was 100 m / min, the rolling tension was 0.004 kN / m, and the rolling speed was 80 m / min.

[0066] Comparative Example 1 1. 160 mL of N-methylpyrrolidone and 40 mL of tetrahydrofuran were mixed, 50 g of single-walled carbon nanotubes were added, and a stable solution was formed by stirring at 30℃.

[0067] Gradient heating: first stage, normal pressure heating, temperature range 40~60℃, heating rate 2℃ / min, 200 rpm stirring, condensing and recovering evaporated gas; second stage, negative pressure-0.05 MPa heating, temperature range 60~80℃, heating rate 1℃ / min, 100 rpm stirring, condensing and recovering evaporated gas; third stage, negative pressure-0.09 MPa heating, temperature range 80~110℃, heating rate 0.5℃ / min, condensing and recovering evaporated gas.

[0068] 2. The 10x10 cm plastic substrate was washed and dried, the surface of the plastic substrate was activated by oxygen plasma treatment at a power of 50 W for 3 min, the temperature of the plastic substrate was controlled at 70℃, the precursor solution was delivered by a precision constant flow liquid supply system, the precursor solution was sprayed onto the plastic substrate by an ultrasonic spraying system, argon gas was introduced for protection, the spraying distance was 10 cm, the flow control was 0.5 mL / min, the carrier gas pressure was 0.1 MPa, and the spraying thickness was 20 um.

[0069] Gradient drying: first stage, 20 min, 25℃, 80% humidity; second stage, 30 min, 40℃, 50%; third stage, 15 min, 60℃, 20% humidity, to obtain the film.

[0070] The obtained film was annealed at 250℃ for 1h under argon protection to obtain the single-walled carbon nanotube film.

[0071] 3. The single-walled carbon nanotube film was peeled off from the plastic substrate and rolled up, the peeling angle of mechanical peeling was 30°, and the peeling was controlled by an industrial grade rolling machine with a tension of 0.004 kN / m.

[0072] A layer of aluminum film is sputtered on both sides of the single-walled carbon nanotube film. Four aluminum targets with a purity of 99.999% are loaded in a roll-to-roll PVD magnetron sputtering device. The vacuum chamber is pumped to a pressure of 10 -4 After 10 Pa, the power of the power supply is adjusted to 9 KW, the voltage is 507 V, and the winding speed is 0.3 m / min. At this time, the thickness of the aluminum film is 0.6 um.

[0073] Comparative Example 2 The operation is basically the same as Comparative Example 1, except that the operation after the single-walled carbon nanotube film is peeled off from the plastic substrate is changed to: a layer of copper film is sputtered on both sides. Four copper targets with a purity of 99.999% are loaded in a roll-to-roll PVD magnetron sputtering device. The vacuum chamber is pumped to a pressure of 10 -4 After 10 Pa, the power of the power supply is adjusted to 9 KW, the voltage is 507 V, and the winding speed is 0.3 m / min. At this time, the thickness of the aluminum film is 0.6 um.

[0074] Comparative Example 3 1. Mix 160 mL of N-methylpyrrolidone with 40 mL of tetrahydrofuran, add 50 g of single-walled carbon nanotubes, and stir at 30°C to form a stable solution.

[0075] Gradient heating: first stage, atmospheric pressure heating, temperature range 40~60℃, heating rate 2℃ / min, 200 rpm stirring, condensing and recovering evaporated gas; second stage, negative pressure-0.05 MPa heating, temperature range 60~80℃, heating rate 1℃ / min, 100 rpm stirring, condensing and recovering evaporated gas; third stage, negative pressure-0.09 MPa heating, temperature range 80~110℃, heating rate 0.5℃ / min, condensing and recovering evaporated gas.

[0076] 2. Clean and dry a 10x10 cm plastic substrate, activate the surface of the plastic substrate with an oxygen plasma treatment for 3 min at a power of 50 W, control the temperature of the plastic substrate at 70℃, deliver the precursor solution through a precision constant-flow liquid supply system, spray the precursor solution onto the plastic substrate using an ultrasonic spraying system, introduce argon gas as a carrier gas, spray distance: 10 cm, flow control: 0.5 mL / min, carrier gas pressure: 0.1 MPa, spray thickness: 20 um.

[0077] Gradient drying: first stage, 20 min, 25℃, 80% humidity; second stage, 30 min, 40℃, 50%; third stage, 15 min, 60℃, 20% humidity, to obtain the film.

[0078] The obtained film is annealed at 250℃ for 1 h under argon protection to obtain a single-walled carbon nanotube film.

[0079] 3. The single-walled carbon nanotube film was peeled off from the plastic substrate and rolled up. The mechanical peeling was performed at a peeling angle of 30°, and the industrial-grade rolling machine was controlled at a tension of 0.004 kN / m.

[0080] Comparative Example 4 The operation was substantially the same as in Example 2, except that the modification of the carbon black with a strong acid in Step 1 was removed, and 5 g of unmodified carbon black was added to the precursor solution in Step 3.

[0081] Comparative Example 5 The operation was substantially the same as in Example 2, except that Step 2 was removed, and no nano-silver was added in Step 3.

[0082] Comparative Example 6 The operation was substantially the same as in Example 2, except that Step 2 was removed, and 68 mg of nano-silver was directly added in Step 3.

[0083] Comparative Example 7 The operation was substantially the same as in Example 2, except that the annealing process in Step 4 was removed.

[0084] The following is a comparison of the product performance test results of each example and comparative example.

[0085] Table 1 is the performance test method and standard.

[0086]

[0087] Table 2 is a comparison of performance test results

[0088] The following is an analysis of the product performance test results of each example and comparative example.

[0089] Comparative Example 1 and Comparative Example 2 used the existing technology of sputtering an aluminum layer or a copper layer on the outer layer of a pure single-walled carbon nanotube film, which effectively improved the resistivity and mechanical properties compared to the pure single-walled carbon nanotube film in Comparative Example 3, with the advantages of super-high conductivity and high rigidity. However, compared to the samples of Example 1, Example 2, and Example 3, the areal density was significantly higher, and the bending life results also showed that the flexibility was poor, making it unsuitable for lightweight and flexible new batteries.

[0090] The carbon black in Comparative Example 4 was not acid-treated, which caused hydrophobic agglomeration, and the dispersion effect of the oxygen-containing functional groups was lost, resulting in an increase in the sedimentation rate of graphene-nano-silver, which could not effectively build a compensation network, leading to a decrease in conductivity. The hydrogen bond cross-linking effect provided by the oxygen-containing functional groups was lost, resulting in a decrease in intermolecular forces, which directly affected the mechanical properties.

[0091] The nano-silver in Comparative Example 5 is not added, and the "metallic electronic bridge" function of the nano-silver is lost, the electronic conduction returns to the pure carbon material contact mode, and the part of the electrical conductivity sacrificed by the introduction of the oxygen-containing functional groups cannot be compensated.

[0092] In Comparative Example 6, the nano-silver is not wrapped and is agglomerated due to van der Waals forces, and is unevenly distributed in the film. However, the electrical conductivity of the sample produced just now can still meet the standard, but the naked nano-silver is easy to be oxidized to Ag2O due to the lack of protection of graphene, which seriously affects the electrical conductivity. Moreover, due to the large size of the agglomerates, the stress concentration effect is enhanced, which is directly reflected in the partial decrease of the tensile strength and the significant decrease of the bending life.

[0093] In Comparative Example 7, the annealing operation is not performed, resulting in too high content of the oxygen-containing functional groups in the sample, and the sacrificed electrical conductivity cannot be completely compensated by reducing the agglomeration degree and introducing graphene-nano-silver. Moreover, the residual solvent forms part of the insulating microzones in the film, increases the electron scattering, and directly affects the electrical conductivity. Moreover, the residual solvent leads to the increase of the area density; although the high content of the oxygen-containing functional groups provides additional crosslinking and enhances the mechanical properties, the slow evaporation of the solvent over time produces micropores, which will also affect the rigidity and flexibility to some extent.

[0094] In summary, the strong acid as a strong oxidizing agent introduces the oxygen-containing functional groups, increases the polarity of the reaction system, improves the dispersibility of the carbon black and the single-walled carbon nanotubes in the preparation of the precursor solution, reduces the agglomeration degree of the effective single-walled carbon nanotubes, makes the carbon black and the single-walled carbon nanotubes more uniformly distributed, and improves the electrical conductivity of the final product. The oxygen-containing functional groups in the modified carbon black powder can improve the viscosity between the molecules in the final composite single-walled carbon nanotube film, and at the same time, reduce the agglomeration of the single-walled carbon nanotubes, improve the electrical conductivity on the macro level while improving the mechanical properties.

[0095] The nano-silver is dispersed in the carbon molecules to establish a "metallic electronic bridge" and compensate for the part of the electrical conductivity sacrificed by the introduction of the oxygen-containing functional groups; the graphene-nano-silver is compounded, the oxidation sensitivity of the nano-silver is significantly reduced by the carrier protection of the graphene, the comprehensive stability is higher than that of the silver element, the oxidation speed of the nano-silver in the current collector is reduced, and the service life of the product current collector is prolonged.

[0096] The annealing process removes the residual solvent in the composite film, removes part of the oxygen-containing functional groups, so that the content of the oxygen-containing functional groups in the carbon black in the film is less than 10wt% of the total amount of the carbon black, and the electrical conductivity of the final product is improved.

[0097] The obtained single-walled carbon nanotube film battery current collector has the advantages of lightweight, high flexibility, and high energy density, and the electrical conductivity can meet the needs of the battery current collector, and can be applied to flexible and ultra-light new type batteries.

[0098] The above description of the specific embodiments of the present application is not intended to limit the scope of the present application. Any other corresponding changes and modifications made according to the technical concept of the present application should be included in the scope of protection of the claims of the present application.

Claims

1. A method for preparing a current collector for a single-walled carbon nanotube thin-film battery, characterized in that, Includes the following steps: S1: Carbon black powder is acid-treated with concentrated nitric acid to obtain modified carbon black powder. Carbon black powder and the modified carbon black powder are taken at a mass ratio of 4:1 to form mixed carbon black powder. S2: Silver acetylacetone and graphene oxide are reduced in the same system to generate graphene-silver nanocomposite powder; S3: Take the mixed carbon black powder, the graphene-silver nanocomposite powder and the single-walled carbon nanotube powder, add them to the dispersion liquid, and stir to form a mixed liquid. The mass ratio of the graphene-silver nanocomposite powder to the mixed carbon black powder is 1:50, and the mass ratio of the single-walled carbon nanotube powder to the mixed carbon black powder is 9:

1. Raise the temperature of the mixed liquid to 40°C and then gradually increase the temperature to prepare a precursor liquid. S4: The precursor liquid is sprayed onto a plastic substrate to form a composite film. The composite film is dried by gradient heating and annealed to obtain a composite single-walled carbon nanofilm. S5: Peel, roll up, and cut the composite single-walled carbon nanotube thin film from the plastic substrate to obtain the single-walled carbon nanotube thin film battery current collector.

2. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S1, the specific process of acid treatment is as follows: Weigh carbon black powder, add 65-68% concentrated nitric acid to the carbon black powder at a dropping rate of 5-10 mL / min, the ratio of carbon black powder to concentrated nitric acid is 0.1 g: 1 mL, stir at 100-500 rpm, heat in a water bath to 80-90℃, reflux, and react for 6-10 hours. After the reaction is completed, stop heating and continue stirring until the reaction solution cools to room temperature. Add deionized water to the reaction solution, the amount of deionized water being 10-20 times the volume of the reaction solution. Filter, wash the filter cake with deionized water 6-8 times, and dry to obtain modified carbon black powder.

3. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S2, the specific reduction process is as follows: oleylamine and dibenzyl ether are mixed at a volume ratio of 1:2 and stirred evenly to prepare a mixed solvent. The mixed solvent is added to graphene oxide and heated in a water bath to 30°C. Silver acetylacetone is added, and the reaction is carried out for 2-3 hours. Then, 2 mol / L lithium borohydride tetrahydrofuran solution is added, and the reaction is continued for 0.5-1 hours. The mass ratio of silver acetylacetone to graphene oxide is 1.3:1, and the material-to-liquid ratio of silver acetylacetone to lithium borohydride tetrahydrofuran solution is 0.017 g:1 mL. After the reaction is completed, the mixture is filtered to obtain a solid product. The solid product is washed with 50-75% ethanol, and the amount of 50-75% ethanol added is 100-150 times the volume of the mixed solvent. The mixture is centrifuged, the precipitate is collected, and vacuum dried at room temperature to obtain graphene-silver nanocomposite powder.

4. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S3, the preparation process of the mixture is as follows: N-methylpyrrolidone and tetrahydrofuran are mixed at a volume ratio of 4:1 and stirred to form a dispersion. The mixed carbon black powder and the graphene-silver nanocomposite powder are added to the reaction vessel. The dispersion is added to the reaction vessel and stirred at 30~40℃. While stirring, single-walled carbon nanotube powder is added to form a mixture.

5. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S3, the gradient heating process is as follows: First stage: At atmospheric pressure, the temperature of the mixture is raised from 40℃ to 60℃ at a rate of 1℃ / min, while stirring at 100~200rpm; Second stage: negative pressure -0.05MPa, raise the temperature of the mixture from 60℃ to 80℃ at a rate of 1℃ / min, and stir at 100~200rpm; The third stage: a negative pressure of -0.09 MPa is applied to raise the temperature of the mixture from 80℃ to 110℃ at a rate of 0.5℃ / min.

6. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S4, the specific process of spraying is as follows: the plastic substrate is cleaned and dried, and then treated with 50W oxygen plasma for 2-5 minutes to activate the surface of the plastic substrate; the temperature of the plastic substrate is controlled at 60-80℃, the precursor liquid is delivered through a precision constant flow liquid supply system, and the precursor liquid is sprayed onto the plastic substrate using an ultrasonic spraying system. Argon carrier gas is introduced for protection, the spraying distance is 10-20cm, the flow rate is controlled at 0.1-1mL / min, the carrier gas pressure is 0.1-0.3MPa, and the spraying thickness is 20-25um.

7. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S4, the specific process of gradient temperature drying is as follows: First stage: Place in an environment of 25℃ and 80% humidity for 20 minutes; Second stage: Place in an environment of 40℃ and 50% humidity for 30 minutes; Third stage: Place in an environment of 60℃ and 20% humidity for 15 minutes.

8. The method for preparing a single-walled carbon nanotube thin-film battery current collector according to claim 1, characterized in that, In step S4, the specific annealing process is as follows: the composite film is heat-treated at 200~300℃ for 0.5~1h under argon protection to obtain a composite single-walled carbon nanotube film.

9. A single-walled carbon nanotube thin-film battery current collector prepared by the preparation method according to any one of claims 1-8.

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