CN110127683B - Graphene dispersion liquid and preparation method and application thereof - Google Patents
Graphene dispersion liquid and preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a graphene dispersion liquid and a preparation method and application thereof, wherein the method comprises the following steps: (1) Uniformly mixing graphene with hexadecyl trimethyl ammonium bromide to obtain surface functionalized graphene; (2) Mixing deionized water with the surface functionalized graphene obtained in the step (1), adding a surfactant during first ultrasonic treatment, standing, and performing second ultrasonic treatment to obtain a uniformly mixed solution; (3) Centrifuging the mixed solution obtained in the step (2), and collecting the upper layer liquid to obtain a dispersion liquid; (4) And (4) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to react under the protection of inert gas, and cooling to obtain the graphene dispersion liquid. Graphene in the graphene dispersion liquid obtained by the invention is uniformly dispersed in deionized water, the dispersion efficiency is high, the viscosity is as low as 4239cps, the graphene structure is complete, the prepared graphene dispersion liquid has good conductivity, and the resistivity is as low as 38 omega cm.
Description
Technical Field
The invention belongs to the technical field of conductive materials, relates to a graphene conductive material, and particularly relates to a graphene dispersion liquid and a preparation method and application thereof.
Background
Graphene is a two-dimensional honeycomb carbon material, consisting of carbon atoms arranged in a hexagon. By sp between carbon and carbon atoms 2 The structure is very stable due to hybrid combination. The special structure of graphene gives it many excellent properties. The graphene is the substance with the highest hardness, has excellent mechanical properties, large theoretical specific surface area and outstanding heat-conducting property, has good electrical conductivity, and has electron mobility as high as 20000cm at room temperature 2 V · s. However, the graphene is often agglomerated together due to the large specific surface area of the graphene, so that the adsorption capacity of the graphene is reduced, and the excellent performance of the graphene is influenced, so that the improvement of the performance of the graphene reinforced composite material is influenced.
CN 106115668A discloses a graphene dispersion method and a graphene composite material, in which hard material particles are in a state of vibration fluidization and irregular motion, and a graphene oxide solution is uniformly sprayed on the surfaces of the hard material particles to obtain a uniformly dispersed graphene composite material. Although the method can solve the problem that graphene is easy to agglomerate, the obtained graphene composite material comprises hard material particles and graphene layers with uniformly dispersed and compounded surfaces, and graphene cannot be uniformly dispersed in water.
CN 108726513A discloses a method for preparing a graphene dispersion liquid, which comprises the steps of firstly preparing graphene oxide powder, then performing ultrasonic and homogenate treatment on the graphene powder in a solvent, adding a dispersant and a surfactant, performing ultrasonic treatment again, and finally obtaining the graphene dispersion liquid through centrifugation. However, the method uses ultrasonic wave for multiple times, consumes large energy, easily damages the graphene structure and is not beneficial to improving the performance of the graphene dispersion liquid.
CN 106902701A discloses a graphene dispersant, which is composed of the following components in parts by mass: 1-3 parts of N-methyl pyrrolidone, 1-4 parts of hexadecyl sodium benzene sulfonate, 1-4 parts of sodium dodecyl benzene sulfonate, 1-3 parts of polyvinylpyrrolidone, 1-4 parts of sodium lignosulfonate, 1-4 parts of sodium cholate, 1-2 parts of hexadecyl trimethyl ammonium bromide, 1-3 parts of polyoxyethylene lauryl ether, 1-3 parts of tween 80, 1-3 parts of polyethylene glycol p-isooctyl phenyl ether, 1-4 parts of lysine, 1-3 parts of polyvinyl alcohol, 1-3 parts of polyacrylamide, 1-3 parts of polyacrylic acid, 1-3 parts of polymethacrylic acid and 1-4 parts of polyoxyethylene. Although the graphene dispersing agent can rapidly disperse graphene and ensure that the graphene does not agglomerate for a long time, the dispersing agent used in the method is various and is not beneficial to the stability of the performance of the graphene.
Liu Peng et al published a research progress on graphene homodisperse problems (materials guide, 2016,30 (10): 39-45), which showed that graphene dispersibility was improved by in-situ polymerization, graphene functionalization, graphene modification, sulfonation precipitation or functional group grafting, but no specific operation method was given.
Therefore, the graphene dispersion liquid with good dispersion performance, the preparation method and the application thereof are provided, and the graphene dispersion liquid has important significance for improving the application potential of graphene.
Disclosure of Invention
Aiming at the defects in the prior art, the invention aims to provide the graphene dispersion liquid, the preparation method and the application thereof, the method can uniformly disperse graphene in water, the dispersion efficiency is high, the dispersion stability is good, the method has small damage to the graphene structure, and the prepared graphene dispersion liquid has good dispersion performance and excellent conductivity.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the present invention provides a method for preparing a graphene dispersion, the method comprising the steps of:
(1) Uniformly mixing graphene with hexadecyl trimethyl ammonium bromide to obtain surface functionalized graphene;
(2) Mixing deionized water with the surface functionalized graphene obtained in the step (1), adding a surfactant during first ultrasonic treatment, standing, and performing second ultrasonic treatment to obtain a uniformly mixed solution;
(3) Centrifuging the mixed solution obtained in the step (2), and collecting the upper layer liquid to obtain a dispersion liquid;
(4) And (4) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to react under the protection of inert gas, and cooling to obtain the graphene dispersion liquid.
The graphene is directly dissolved in water, so that graphene is agglomerated, and the conductivity of the graphene is influenced.
Preferably, the mass ratio of the graphene to the cetyltrimethylammonium bromide in the step (1) is 1 (25-35), and can be, for example, 1. Excessive hexadecyl trimethyl ammonium bromide can fully carry out surface modification on graphene through electrostatic attraction, so that the graphene is dissolved in deionized water and then separated from impurity ions, and is not easy to agglomerate.
Preferably, the mixing in step (1) is performed under an oxygen-free condition, and hexadecyl trimethyl ammonium bromide is mixed with the graphene under the oxygen-free condition to prevent the graphene from agglomerating during the mixing process.
Preferably, the temperature of said mixing in step (1) is 10-30 ℃, for example 10 ℃, 15 ℃,20 ℃, 25 ℃ or 30 ℃, preferably 15-20 ℃.
Preferably, the liquid-solid ratio of the deionized water in the step (2) to the surface-functionalized graphene obtained in the step (1) is (500-1500): 1, which can be, for example, 500.
Preferably, the power of the first ultrasonic wave in the step (2) is 270-350W, such as 270W, 280W, 290W, 300W, 310W, 320W, 330W, 340W or 350W, preferably 300-320W.
Preferably, the time of the first ultrasound in step (2) is 50-70min, for example, 50min, 55min, 60min, 65min or 70min, preferably 55-65min.
Preferably, the standing time in step (2) is 20-40min, such as 20min, 25min, 30min, 35min or 40min, preferably 25-35min. The standing can enable the interaction between the surfactant and the hexadecyl trimethyl ammonium bromide to be more sufficient, so that the dispersion effect of the surface functionalized graphene is improved, and the dispersion effect of the secondary ultrasound is better.
Preferably, the power of the second ultrasonic wave in step (2) is 650-750W, such as 650W, 660W, 670W, 680W, 690W, 700W, 710W, 720W, 730W, 740W or 750W, preferably 680-720W.
Preferably, the time of the second ultrasound in step (2) is 50-70min, for example, 50min, 55min, 60min, 65min or 70min, preferably 55-65min.
The surface functionalized graphene is dispersed by combining a low-power first ultrasonic technology and a high-power second ultrasonic technology, the low power is used for carrying out primary ultrasonic treatment on the surface functionalized graphene during the first ultrasonic, and a surfactant is added in the first ultrasonic process, so that the surfactant and cetyl trimethyl ammonium bromide are better interacted, and the dispersion effect of the surface functionalized graphene is improved; the power is higher during the second ultrasonic treatment, and the graphene with functionalized surface under the action of the surfactant has stable structure and is more uniformly dispersed in deionized water during the second ultrasonic treatment.
Preferably, the surfactant of step (2) comprises any one or a combination of at least two of sodium glycocholate, sodium stearate or cocodiethanolamide, typical but non-limiting combinations include a combination of sodium glycocholate and sodium stearate, a combination of sodium stearate and cocodiethanolamide, a combination of sodium glycocholate and cocodiethanolamide or a combination of sodium glycocholate, sodium stearate and cocodiethanolamide, preferably a combination of sodium glycocholate, sodium cocoate and cocodiethanolamide.
Preferably, the mass ratio of sodium glycocholate, sodium cocoate to cocoate diethanolamide is (2-4): 1.
According to the invention, the surfactant with a specific composition is selected to improve the dispersion performance of the prepared graphene dispersion liquid, and when the mass ratio of sodium glycocholate, sodium cocoate and coconut diethanolamide in the surfactant exceeds the numerical range protected by the invention, the dispersion performance of the prepared graphene dispersion liquid is reduced.
Preferably, the mass ratio of the added amount of the surfactant to the surface-functionalized graphene obtained in step (1) is (1-10): 100, and may be, for example, 1.
Preferably, the surfactant is added in step (2) by starting the surfactant addition at 1/3-2/3 of the first sonication and adding the surfactant completely at the end of the first sonication. According to the invention, the surfactant is added in the first ultrasonic process, so that the surfactant can more uniformly interact with cetyl trimethyl ammonium bromide in the surface functionalized graphene under the ultrasonic action, and the dispersion effect of the surfactant on the obtained surface functionalized graphene is improved.
Preferably, the rotation speed of the centrifugation in the step (3) is 80-150r/min, such as 80r/min, 90r/min, 100r/min, 110r/min, 120r/min, 130r/min, 140r/min or 150r/min, preferably 100-120r/min.
Preferably, the centrifugation time is 10-35min, for example 10min, 15min, 20min, 25min, 30min or 35min, preferably 15-30min.
The centrifugation process can remove excessive hexadecyl trimethyl ammonium bromide and remove a small amount of impurity ions possibly existing in the graphene.
Preferably, the mass ratio of the sodium hydride added in the step (4) to the surface-functionalized graphene obtained in the step (1) is (2-4): 100, and for example, the ratio can be 2.
Preferably, the temperature of the reaction of step (4) is 70 to 100 ℃, for example 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃ or 100 ℃, preferably 80 to 90 ℃.
Preferably, the reaction time in step (4) is 90-150min, such as 90min, 100min, 110min, 120min, 130min, 140min or 150min, preferably 120-130min.
Preferably, the inert gas in step (4) includes any one of nitrogen, argon or neon or a combination of at least two of nitrogen, argon or neon.
Preferably, the dispersion liquid formed by mixing the sodium hydride and the dispersion liquid obtained in the step (3) flows circularly when the temperature is raised for reaction in the step (4), so that the mixing effect of each ion in the solution is improved, and the dispersion efficiency is improved.
Preferably, the temperature after cooling in step (4) is 20 to 30 ℃, for example 20 ℃, 21 ℃, 22 ℃, 23 ℃, 24 ℃, 25 ℃, 26 ℃,27 ℃, 28 ℃, 29 ℃ or 30 ℃, preferably 24 to 28 ℃.
As a preferred technical solution of the method according to the first aspect of the present invention, the method comprises the steps of:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to the mass ratio of 1 (25-35) at 10-30 ℃ under an oxygen-free condition to obtain surface functionalized graphene;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio (500-1500): 1, carrying out primary ultrasonic treatment for 50-70min under the power of 270-350W, starting adding a surfactant consisting of sodium glycocholate, sodium cocoate and coconut oil acid diethanolamide according to a mass ratio (2-4): 1 (5-8) when the primary ultrasonic treatment is carried out for 1/3-2/3, completely adding the surfactant when the primary ultrasonic treatment is finished, wherein the mass ratio of the addition amount of the surfactant to the surface functionalized graphene obtained in the step (1) is (1-10): 100, standing for 20-40min, and carrying out secondary ultrasonic treatment for 50-70min under the power of 650-750W to obtain a uniformly mixed solution;
(3) Centrifuging the mixed solution obtained in the step (2) at the rotating speed of 80-150r/min for 10-35min, and collecting the upper layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 70-100 ℃ under the protection of nitrogen, reacting for 90-150min, cooling to 20-30 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is (2-4): 100.
In a second aspect, the present invention provides a graphene dispersion prepared by the method of the first aspect.
In a third aspect, the present invention provides the use of the graphene dispersion according to the second aspect for preparing an electrode slurry.
The numerical ranges set forth herein include not only the recited values but also any values between the recited numerical ranges not enumerated herein, and are not intended to be exhaustive or otherwise clear from the intended disclosure of the invention in view of brevity and clarity.
Compared with the prior art, the invention has the beneficial effects that:
(1) The preparation method of the graphene dispersion liquid is simple, the graphene is uniformly dispersed in the deionized water through the coordination of the hexadecyl trimethyl ammonium bromide and the specific surfactant, the dispersion efficiency is high, the dispersion performance is good, and the viscosity of the prepared graphene dispersion liquid is as low as 4239cps;
(2) The centrifugation used in the preparation process of the graphene dispersion liquid is an auxiliary means for separating excessive hexadecyl trimethyl ammonium bromide and possibly existing impurity ions, and the centrifugation rotating speed is low; and the graphene is dispersed by adopting a step-by-step ultrasonic method, the structural integrity of the graphene is ensured, the prepared graphene dispersion liquid has good conductivity, and the resistivity is as low as 38 omega cm.
Detailed Description
The technical solution of the present invention is further explained by the following embodiments.
Example 1
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water with the surface-functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1000, carrying out primary ultrasonic treatment for 60min under the power of 310W, adding a surfactant consisting of sodium glycocholate, sodium cocoate and coconut diethanolamide according to a mass ratio of 3;
(3) Centrifuging the mixed solution obtained in the step (2) for 25min at the rotating speed of 110r/min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (2) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 85 ℃ under the protection of nitrogen, reacting for 125min, and cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
Example 2
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water with the surface-functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1000, carrying out primary ultrasonic treatment for 60min under the power of 310W, adding a surfactant consisting of sodium glycocholate, sodium cocoate and coconut diethanolamide according to a mass ratio of 3;
(3) Centrifuging the mixed liquid obtained in the step (2) at the rotating speed of 110r/min for 25min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 85 ℃ under the protection of nitrogen, reacting for 125min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
Example 3
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1000, carrying out primary ultrasonic treatment for 60min under a power of 310W, starting to add a surfactant consisting of sodium glycocholate, sodium cocoate and coconut diethanolamide according to a mass ratio of 3;
(3) Centrifuging the mixed liquid obtained in the step (2) at the rotating speed of 110r/min for 25min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 85 ℃ under the protection of nitrogen, reacting for 125min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
Example 4
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1200, carrying out primary ultrasonic treatment for 55min under the power of 320W, starting to add a surfactant consisting of sodium glycocholate, sodium cocoate and coconut diethanolamide according to a mass ratio of 2;
(3) Centrifuging the mixed solution obtained in the step (2) for 15min at the rotating speed of 120r/min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 90 ℃ under the protection of nitrogen, reacting for 120min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
Example 5
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to the mass ratio of 1;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 800, carrying out primary ultrasonic treatment at a power of 300W for 65min, starting adding a surfactant consisting of sodium glycocholate, sodium cocoate and coconut oil acid diethanolamide according to a mass ratio of 4;
(3) Centrifuging the mixed solution obtained in the step (2) for 30min at the rotating speed of 100r/min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 80 ℃ under the protection of nitrogen, reacting for 130min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
Example 6
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1500, carrying out primary ultrasonic treatment for 50min under 350W, starting to add a surfactant consisting of sodium glycocholate, sodium cocoate and cocoic acid diethanolamide according to a mass ratio of 2;
(3) Centrifuging the mixed liquid obtained in the step (2) at the rotating speed of 150r/min for 10min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 70 ℃ under the protection of nitrogen, reacting for 150min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 4.
Example 7
The embodiment provides a preparation method of a graphene dispersion liquid, which comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 500;
(3) Centrifuging the mixed solution obtained in the step (2) for 35min at the rotating speed of 80r/min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 100 ℃ under the protection of nitrogen, reacting for 90min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 2.
Example 8
This example provides a method for preparing a graphene dispersion, which is the same as example 3 except that in step (2), the surfactant is composed of 3.
Example 9
This example provides a preparation method of a graphene dispersion, which is the same as example 3 except that in step (2), the surfactant is composed of 3.
Example 10
This example provides a method for preparing a graphene dispersion, which is the same as example 3 except that in step (2), the surfactant is composed of 1.
Comparative example 1
The present comparative example provides a method of preparing a graphene dispersion, the method comprising the steps of:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water and the surface-functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1000, performing ultrasonic treatment at 700W for 120min, starting adding a surfactant consisting of sodium glycocholate, sodium cocoate and cocoic acid diethanolamide according to a mass ratio of 3;
(3) Centrifuging the mixed liquid obtained in the step (2) at the rotating speed of 110r/min for 25min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 85 ℃ under the protection of nitrogen, reacting for 125min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
Comparative example 2
The present comparative example provides a method of preparing a graphene dispersion, the method comprising the steps of:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to a mass ratio of 1;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio of 1000, performing ultrasonic treatment at a power of 310W for 120min, starting adding a surfactant consisting of sodium glycocholate, sodium cocoate and cocoic acid diethanolamide according to a mass ratio of 3;
(3) Centrifuging the mixed solution obtained in the step (2) for 25min at the rotating speed of 110r/min, and collecting the upper-layer liquid to obtain a dispersion liquid;
(4) And (3) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 85 ℃ under the protection of nitrogen, reacting for 125min, cooling to 25 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is 3.
The solid content, viscosity, and resistivity of the graphene dispersions prepared in examples 1 to 10 and comparative examples 1 to 2 were measured.
Wherein the solid content measurement conditions are as follows: weighing an empty watch glass, wherein the weight is recorded as m1, smearing 3g of slurry on the surface of the watch glass, weighing the empty watch glass, wherein the weight is recorded as m2, putting the watch glass coated with the slurry into a 140 ℃ oven, drying the watch glass for 0.5h, cooling the watch glass to room temperature, and weighing the watch glass again, wherein the weight is recorded as m3, and then the solid content is = (m 3-m 1)/(m 2-m 1). Times.100 percent.
The conditions for measuring the viscosity were: mechanically stirred at 750rpm for 3min, the rotational viscometer # 4 spindle was inserted into the slurry at room temperature and tested at 12rpm, after the number on the viscometer scale had stabilized.
The conditions for measuring the resistivity were that the graphene dispersions prepared in examples 1 to 10 and comparative examples 1 to 2 were applied to a PI film using a 200 μm doctor blade after homogenization, dried at 140 ℃ for 1 hour, and then tested using a four-probe tester of type RTS-8, and 9 points were symmetrically taken, and the average of the resistivities measured at the 9 points was the obtained value.
The measurement data of the solid content, viscosity and resistivity are shown in table 1.
TABLE 1
As can be seen from Table 1, the graphene dispersions prepared in examples 1 to 7 of the present invention have a solid content of 54.97 to 59.84%, a viscosity of 4239 to 5439cps, and a resistivity of 38 to 56. Omega. M.
Example 8 provides a method for preparing a graphene dispersion, and compared to example 3, the surfactant in example 8 is not added with sodium cocoate, and when the solid content of the obtained graphene dispersion is 53.09%, the viscosity is increased to 5618cps, and the resistivity is increased to 67 Ω · m. The conductivity of the electrode slurry prepared from the graphene dispersion liquid provided in example 8 is slightly inferior to that of the battery slurry prepared from the graphene dispersion liquid provided in example 1.
Example 9 provides a method for preparing a graphene dispersion, and compared with example 3, the surfactant in example 9 is not added with coconut diethanolamide, and when the solid content of the obtained graphene dispersion is 57.15%, the viscosity is increased to 5936cps, and the resistivity is increased to 62 Ω · m. The conductivity of the electrode slurry prepared from the graphene dispersion liquid provided in example 9 is slightly inferior to the conductivity of the battery slurry prepared from the graphene dispersion liquid provided in example 1.
Example 10 provides a method for preparing a graphene dispersion, and when the surfactant in example 10 is not added with sodium glycocholate, the solid content of the obtained graphene dispersion is 56.72%, the viscosity is increased to 5749cps, and the resistivity is increased to 71 Ω · m, compared with example 3. The conductivity of the electrode slurry prepared from the graphene dispersion liquid provided in example 10 is slightly inferior to that of the battery slurry prepared from the graphene dispersion liquid provided in example 1.
From examples 8 to 10, it is understood that the composition of the surfactant has an important influence on the viscosity and resistivity of the finally obtained graphene dispersion, and when the composition of the surfactant is sodium glycocholate, sodium cocoate and cocodiethanolamide in a mass ratio of (2-4): 1 (5-8), the viscosity of the obtained graphene dispersion is low, 4239-5439cps, and the resistivity is low, 38-56 Ω · m.
Comparative example 1 provides a method for preparing a graphene dispersion, and compared to example 3, in comparative example 1, a stepwise ultrasonic method was not used, and ultrasonic treatment was performed at a power of 700W for 120min, and the obtained graphene dispersion had a solid content of 58.52% but a viscosity increased to 7150cps and a conductivity increased to 73 Ω · m.
Comparative example 2 provides a method for preparing a graphene dispersion, and compared to example 3, in comparative example 2, the step-wise ultrasonic method is not adopted, but ultrasonic processing is performed at a power of 310W for 120min, and the obtained graphene dispersion has a solid content of 56.96%, but the viscosity is increased to 7327cps, and the conductivity is increased to 72 Ω · m.
In conclusion, the preparation method of the graphene dispersion liquid is simple, the graphene is uniformly dispersed in the deionized water through the coordination of the hexadecyl trimethyl ammonium bromide and the specific surfactant, the dispersion efficiency is high, the dispersion performance is good, and the viscosity of the prepared graphene dispersion liquid is as low as 4239cps; and the graphene is dispersed by adopting a step-by-step ultrasonic method, the integrity of the graphene structure is ensured, the prepared graphene dispersion liquid has good conductivity, and the resistivity is as low as 38 omega cm.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only examples of the present invention, and should not be construed as limiting the present invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (31)
1. A preparation method of a graphene dispersion liquid is characterized by comprising the following steps:
(1) Uniformly mixing graphene and hexadecyl trimethyl ammonium bromide under an anaerobic condition to obtain surface functionalized graphene;
(2) Mixing deionized water with the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio (500-1500): 1, adding a surfactant during first ultrasonic treatment, standing, and then performing second ultrasonic treatment to obtain a uniformly mixed solution;
(3) Centrifuging the mixed solution obtained in the step (2), and collecting the upper layer liquid to obtain a dispersion liquid;
(4) Mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to react under the protection of inert gas, and cooling to obtain the graphene dispersion liquid;
the mass ratio of the graphene to the hexadecyl trimethyl ammonium bromide in the step (1) is 1 (25-35);
the power of the first ultrasonic wave in the step (2) is 270-350W;
the power of the second ultrasonic wave in the step (2) is 650-750W;
the surfactant in the step (2) is a combination of sodium glycocholate, sodium cocoate and coconut diethanolamide;
the mass ratio of the sodium glycocholate to the sodium cocoate to the coconut diethanolamide is (2-4) to 1 (5-8).
2. The method according to claim 1, wherein the mass ratio of the graphene to the cetyltrimethylammonium bromide in the step (1) is 1 (27-32).
3. The method of claim 1, wherein the temperature of the mixing of step (1) is 10-30 ℃.
4. The method of claim 3, wherein the temperature of the mixing of step (1) is 15-20 ℃.
5. The method according to claim 1, wherein the liquid-solid ratio of the deionized water in the step (2) to the surface functionalized graphene obtained in the step (1) is (800-1200): 1.
6. The method of claim 1, wherein the power of the first ultrasound in step (2) is 300-320W.
7. The method of claim 1, wherein the time of the first ultrasound in step (2) is 50-70min.
8. The method of claim 7, wherein the time of the first ultrasound in step (2) is 55-65min.
9. The method of claim 1, wherein the standing time in step (2) is 20-40min.
10. The method of claim 9, wherein the standing time of step (2) is 25-35min.
11. The method of claim 1, wherein the power of the second ultrasound in step (2) is 680-720W.
12. The method of claim 1, wherein the time of the second ultrasound in step (2) is 50-70min.
13. The method of claim 12, wherein the second ultrasound of step (2) is performed for a period of 55-65min.
14. The method according to claim 1, wherein the mass ratio of the added amount of the surfactant in the step (2) to the surface-functionalized graphene obtained in the step (1) is (1-10): 100.
15. The method according to claim 14, wherein the mass ratio of the added amount of the surfactant in the step (2) to the surface-functionalized graphene obtained in the step (1) is (2-6): 100.
16. The method of claim 1, wherein the adding of the surfactant in the step (2) is started when the first ultrasonic treatment is performed by 1/3 to 2/3, and is completely added when the first ultrasonic treatment is performed.
17. The method according to claim 1, wherein the rotation speed of the centrifugation in the step (3) is 80-150r/min.
18. The method of claim 17, wherein the rotation speed of the centrifugation in step (3) is 100-120r/min.
19. The method of claim 1, wherein the centrifugation of step (3) is performed for a period of 10-35min.
20. The method of claim 19, wherein the centrifugation of step (3) is carried out for a period of 15-30min.
21. The method according to claim 1, wherein the mass ratio of the added amount of the sodium hydride in the step (4) to the surface-functionalized graphene obtained in the step (1) is (2-4): 100.
22. The method according to claim 21, wherein the mass ratio of the sodium hydride added in the step (4) to the surface-functionalized graphene obtained in the step (1) is 3.
23. The method of claim 1, wherein the temperature of the reaction of step (4) is 70-100 ℃.
24. The method of claim 23, wherein the temperature of the reaction of step (4) is 80-90 ℃.
25. The method of claim 1, wherein the reaction time of step (4) is 90-150min.
26. The method of claim 25, wherein the reaction time in step (4) is 120-130min.
27. The method of claim 1, wherein the temperature after cooling in step (4) is 20-30 ℃.
28. The method of claim 27, wherein the post-cooling temperature of step (4) is 24-28 ℃.
29. Method according to claim 1, characterized in that it comprises the following steps:
(1) Mixing graphene and hexadecyl trimethyl ammonium bromide according to the mass ratio of 1 (25-35) at 10-30 ℃ under an oxygen-free condition to obtain surface functionalized graphene;
(2) Mixing deionized water and the surface functionalized graphene obtained in the step (1) according to a liquid-solid ratio (500-1500): 1, carrying out primary ultrasonic treatment for 50-70min under the power of 270-350W, starting adding a surfactant consisting of sodium glycocholate, sodium cocoate and coconut oil acid diethanolamide according to a mass ratio (2-4): 1 (5-8) when the primary ultrasonic treatment is carried out for 1/3-2/3, completely adding the surfactant when the primary ultrasonic treatment is finished, wherein the mass ratio of the addition amount of the surfactant to the surface functionalized graphene obtained in the step (1) is (1-10): 100, standing for 20-40min, and carrying out secondary ultrasonic treatment for 50-70min under the power of 650-750W to obtain a uniformly mixed solution;
(3) Centrifuging the mixed solution obtained in the step (2) at the rotating speed of 80-150r/min for 10-35min, and collecting the upper layer liquid to obtain a dispersion liquid;
(4) And (4) mixing sodium hydride with the dispersion liquid obtained in the step (3), heating to 70-100 ℃ under the protection of nitrogen, reacting for 90-150min, cooling to 20-30 ℃ to obtain the graphene dispersion liquid, wherein the mass ratio of the addition amount of the sodium hydride to the surface functionalized graphene obtained in the step (1) is (2-4): 100.
30. A graphene dispersion prepared according to the method of any one of claims 1-29.
31. Use of the graphene dispersion according to claim 30 for preparing an electrode slurry.
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