CN115924897A - Device and method for centrifugally stripping single-layer/few-layer graphene dispersion liquid - Google Patents
Device and method for centrifugally stripping single-layer/few-layer graphene dispersion liquid Download PDFInfo
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
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- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to the technical field of graphene production, in particular to a device and a method for centrifugally stripping single-layer/few-layer graphene dispersion liquid; the device comprises a centrifugal stripping device and a pre-dispersing tank, wherein the centrifugal stripping device is connected with the pre-dispersing tank through a material circulating pipeline; the centrifugal stripping device comprises a tank body, a rotor is arranged in the tank body, the rotor comprises a central shaft and blades arranged on the central shaft and arranged along the circumferential direction of the central shaft, the central shaft is connected with a first motor, and the distance between the outer end parts of the blades and the inner wall of the tank body is 1-3mm; the device for centrifugally stripping the single-layer/few-layer graphene dispersion liquid greatly enhances the synchronism of the centrifugal motion of the medium driven by the rotating rotor, and ensures the relative consistency and uniformity of the motion track of the medium.
Description
Technical Field
The invention relates to the technical field of graphene production, in particular to a device and a method for centrifugally stripping single-layer/few-layer graphene dispersion liquid.
Background
The graphene dispersion liquid is convenient to use, can be added into a composite material system by simple stirring, and is gradually accepted in practical production application.
At present, the preparation method of the graphene dispersion liquid mainly comprises 2 methods:
one method is to modify graphene powder, mix the modified graphene powder with a dispersant solvent, prepare a graphene dispersion liquid by means of high-speed stirring/ultrasound/grinding and the like, and the high-speed stirring/ultrasound/shearing/grinding mainly has the functions of infiltrating large particles of the graphene powder, performing micron-scale secondary aggregation and nano-scale primary aggregation on the graphene powder, and performing depolymerization. The graphene prepared by the method has a plurality of defects, and the process has influence on the environment.
The other method is a method utilizing mechanical stripping, namely, graphite sheets are directly opened in a liquid phase through mechanical stripping acting force to be stripped into graphene dispersion liquid. The raw materials of the method are graphite and expanded graphite with certain van der Waals acting force between layers, and the dispersing equipment is mainly an ultrasonic/homogenizing/grinding machine and the like. The ultrasonic treatment mainly comprises the steps of utilizing an intercalation expansion reagent to enter a graphite layer and then performing strong ultrasonic oscillation to expand and open a graphite sheet layer; homogeneity has super strong cavitation, vibration, impact and shearing acting force, can destroy molecular bond force, and often quickly shears large graphite and expanded graphite particles into small particles; the grinding machine, whether a disc type, a turbine or a pin, has a large gap between a central rotor and an inner cavity, expands the centrifugal friction force of a medium from the center of a circle to the outside, weakens the movement strength of an edge zone, has poor uniformity, and is often used for depolymerizing large particles, small aggregates and secondary particles of graphite/expanded graphite. Therefore, graphene dispersion liquid obtained by the existing mechanical stripping method basically has a small particle size of 5-40um, the probability of 10 layers or less is low, 10-20 layers are more, and 20-100 layers of graphite micro-sheets are common, so that the problems of thick sheet layer, more layers, easy sedimentation and the like are caused, and the electrochemical performance is unstable and is good and bad.
Therefore, the graphite flake has less than 10 flakes, more single/few flakes, uniform distribution, less defects, moderate particle size, and very urgent is the exfoliation technology and product for precisely controlling exfoliated graphite flakes.
Disclosure of Invention
The purpose of the invention is: an apparatus for centrifugally peeling a single/few-layer graphene dispersion is provided to solve at least one of the above technical problems.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a device for centrifugally stripping single-layer/few-layer graphene dispersion liquid comprises a centrifugal stripping device and a pre-dispersion tank, wherein the centrifugal stripping device is connected with the pre-dispersion tank through a material circulating pipeline;
the centrifugal stripping device comprises a tank body, a rotor is arranged in the tank body, the rotor comprises a central shaft and blades which are arranged on the central shaft and are arranged at equal intervals along the circumferential direction of the central shaft, the central shaft is connected with a first motor, the distance between the outer end parts of the blades and the inner wall of the tank body is 1-3mm, and the diameter of the inner cavity of the tank body is 234 +/-2 mm.
Furthermore, a low-speed stirring device and a high-speed stirring device are arranged in the pre-dispersion tank.
Furthermore, the peripheries of the pre-dispersing tank and the centrifugal stripping device are provided with circulating cooling jackets.
Further, the shape of the blades is annular, and the distance between adjacent blades is larger than the arc length of the blades.
Further, the centrifugal stripping device is filled with a centrifugal medium, the filling amount of the centrifugal medium is 80% of the volume of the cavity, and the diameter of the centrifugal medium is 0.3-1.0mm.
Another object of the invention is: provided is a centrifugal separation method for an apparatus for centrifugally separating a single-layer/few-layer graphene dispersion, which is used to solve at least one of the above technical problems.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows:
a centrifugal exfoliation method of an apparatus for centrifugally exfoliating a single/few-layer graphene dispersion, the centrifugal exfoliation method comprising the steps of:
filling a centrifugal medium in a centrifugal stripping device, adding graphite powder, a dispersing agent and a solvent in a pre-dispersing device, stirring and dispersing, conveying the materials into the centrifugal stripping device through a circulating pipeline, setting centrifugal stripping parameters, carrying out centrifugal motion on the materials and the medium in a centrifugal stripping cavity, connecting the materials and the medium with the pre-dispersing tank in series for closed loop, carrying out circulating motion for 6 +/-0.5 h, and then discharging the products for parameter evaluation.
Furthermore, the centrifugal speed in the centrifugal parameters is 500-3000rpm, the speed is low firstly and then high, and the temperature in the cavity does not exceed 70 ℃ in the centrifugal stripping process.
Furthermore, the particle size of the graphite powder is 50-100 meshes, and the expansion ratio is 200-600 times.
Further, the solvent is one or a combination of more of N-methyl pyrrolidone (NMP), ethanol, isopropanol and water; dispersing agent polyvinylpyrrolidone PVP and its modified copolymer, polyvinylidene fluoride and its modified copolymer, polyacrylic acid and its modified copolymer.
Further, the mass ratio of the graphite powder to the dispersing agent is 1.26.
The technical scheme adopted by the invention has the beneficial effects that:
according to the device for centrifugally stripping the single-layer/few-layer graphene dispersion liquid, the distance between the outer end of each blade and the inner wall of the tank body is set to be 1-3mm, so that the synchronism of a medium driven by a rotating rotor to centrifugally move is greatly enhanced, and the relative consistency and uniformity of the movement track of the medium are ensured.
The filling amount of a centrifugal medium in the centrifugal stripping device is 80% of the volume of the cavity, the diameter of the centrifugal medium is 0.3mm, and when the centrifugal linear speed is 11m/s, the single-layer/few-layer graphene dispersion liquid with 3-5 layers can be stripped in a large batch, so that the stable and large-batch production of the high-quality single-layer/few-layer graphene dispersion liquid is realized.
Drawings
FIG. 1 is a schematic view of a centrifugal peeling apparatus according to the present invention;
FIG. 2 is a schematic diagram of the centrifugal motion friction of the medium 1, the medium 2, the medium 3 and the medium 4 in the inner cavity of the centrifugal peeling device (R is the radius of the grinding cavity, R is the radius of the medium, and the collision friction among the medium 1, the medium 2, the medium 3 and the medium 4 is the centrifugal motion friction force F);
FIG. 3 experiment 1 product SEM of centrifugal 0.3mm media and material from a centrifugal stripping apparatus;
FIG. 4 experiment 1 centrifugal peeling apparatus centrifuge product TEM of 0.3mm media and material;
FIG. 5 product SEM of experiment 2 centrifugal 0.6mm media and material from the centrifugal peel device;
FIG. 6 product SEM of comparative experiment 1, 25CE pin mill centrifuging 0.3mm media versus material;
FIG. 7 product TEM of comparative experiment 1, 25CE pin mill centrifuged 0.3mm media and material;
figure 8 product SEM of comparative experiment 2, 25CE pin mill centrifugation 0.6mm media versus material.
In the figure: 1. the device comprises a central shaft, 2, a rotor, 3, a motor I, 4, a material circulating pipeline, 5, a high-speed stirring paddle, 6, a circulating cooling jacket, 7, a low-speed stirring paddle, 8, an electromagnetic valve, 9, a pump body, 10, a low-speed motor, 11 and a high-speed motor.
Detailed Description
The present invention is not limited to the following embodiments, and those skilled in the art can implement the present invention in other embodiments according to the disclosure of the present invention, or make simple changes or modifications on the design structure and idea of the present invention, and fall into the protection scope of the present invention. It should be noted that the embodiments and features of the embodiments may be combined with each other without conflict.
Referring to fig. 1, the apparatus for centrifugally stripping a single-layer/few-layer graphene dispersion according to the present invention includes a centrifugal stripping apparatus and a pre-dispersion tank, the centrifugal stripping apparatus and the pre-dispersion tank are connected through a material circulation pipeline 4, a circulation pump body 9 is installed on the material circulation pipeline 4, the circulation pump body 9 according to the present invention is a diaphragm pump, and an electromagnetic valve 8 is installed on a pipeline between the pre-dispersion tank and the circulation pump body 9; the centrifugal stripping device comprises a tank body, a rotor 2 is arranged in the tank body, the rotor 2 comprises a central shaft 1 and blades which are arranged on the central shaft 1 and arranged along the circumferential direction of the central shaft, the central shaft 1 is connected with a motor I3, and the distance between the outer end parts of the blades and the inner wall of the tank body is 1-3mm, specifically 1mm, 1.2mm, 1.5mm, 1.8mm, 2mm, 2.2mm, 2.5mm, 2.8mm and 3mm; install low-speed agitating unit and high-speed agitating unit in the predispersion jar in advance, set up low-speed agitating unit and high-speed agitating unit simultaneously in the predispersion jar, can be with material intensive mixing, low-speed agitating unit includes the (mixing) shaft, low-speed stirring rake 7 and installs the low-speed motor 10 at the predispersion tank top in advance, high-speed agitating unit includes the (mixing) shaft, high-speed stirring rake 5 and installs the high-speed motor 11 at the predispersion tank top in advance, the circulative cooling presss from both sides cover 6 is installed to the periphery of predispersion jar and centrifugal stripping off device in advance. The inner diameter of the centrifugal stripping device is 234mm, and a centrifugal medium with the diameter of 0.3-1.0mm and 80% of the volume of the cavity is filled in the centrifugal stripping device.
1. The working principle of the device for centrifugally stripping the single-layer/few-layer graphene dispersion liquid is as follows: graphite powder, a dispersing agent and a solvent are fully stirred and dispersed in a pre-dispersing tank through a high-speed stirring device and a low-speed stirring device, then the mixture is pumped into an inner cavity of a centrifugal stripping device through a pump body 9, a rotor 2 rotating at a high speed is driven through a motor I3, and the high-strength centrifugal motion friction force is generated in cooperation with the medium in the inner cavity to perform a friction stripping effect on a processed material. The materials to be processed are subjected to centrifugal friction stripping for multiple times, and then are stirred at high and low speeds in the tank body, so that the materials can be uniformly soaked, sheared and subjected to centrifugal friction stripping treatment.
In addition, high-speed centrifugal friction can produce great heat, and install circulative cooling jacket 6 additional in the device inner chamber periphery to take away the heat through circulative cooling jacket 6, alleviateed the influence of high temperature to the processing material.
Fig. 2 is a schematic diagram of centrifugal motion friction of media 1, 2, 3 and 4 in the inner cavity of the centrifugal peeling device (R is the radius of the grinding cavity, R is the radius of the media, and collision friction among the media 1, 2, 3 and 4 is centrifugal motion friction force F).
2. The centrifugal peel strength in the present invention was evaluated as follows:
the medium centrifugally moves in the cavity of the centrifugal stripping device, the medium is impacted and rubbed with each other in the moving process to generate strong centrifugal movement friction force, calculation is carried out according to the centrifugal movement track, and the centrifugal friction strength
The following were used: />
F 1 Is the centrifugal kinetic friction of No. 1 medium, F 2 The centrifugal motion friction force of No. 2 medium, the mass of m-ball as medium, the linear velocity of medium in centrifugal motion, F Difference between Is the difference of the centrifugal motion friction force between two media, the S ball is the surface area of the media, the V ball is the volume of a single medium, rho is the density of the media, P is the friction strength between the single media, ni is the number of the media, and m is the total mass of the balls,
is the total friction strength between the media.
According to the above calculation, the centrifugal friction strength between the media is inversely proportional to the square of the radius of the cavity of the centrifugal peeling device, is proportional to the total mass of the media, is inversely proportional to the radius of the media, and is proportional to the square of the linear velocity of the centrifugal movement. 75kg of centrifugal medium (zirconium balls are adopted in the invention) is filled in an inner cavity (the diameter is 234 mm) of the centrifugal stripping device, the medium with different diameters (0.3-1.0 mm) and the material to be processed are replaced, the centrifugal friction strength of the medium is calculated by deduction and shown in table 1 after the medium and the material to be processed are centrifugally moved at the linear speed of 11 m/s. The diameter of the medium is gradually reduced from 1.0mm to 0.3mm, and the centrifugal friction strength is increased from 0.042GPa to 0.141GPa.
Table 1 shows the relationship between the centrifugal friction strength and the diameter of a medium by filling 75kg of the medium into the inner cavity (diameter: 234 mm) of a centrifugal peeling device and performing centrifugal motion at a linear velocity of 11m/s
According to the literature (Z Liu, et al, acta Mechenica Sinica, 2012, 28 (4): 978): the van der Waals acting force of the mutual connection between the graphite sheets is stronger, the peeling strength of the expanded or other treated graphite sheets is 0.2MPa-7GPa, and the tearing strength of the single crystal graphite sheets is about 0.14GPa. Comparing table 1, it can be seen that: 1) When the diameter of the centrifugal medium is equal to 0.3mm, the centrifugal friction strength of the medium in the centrifugal stripping device is equal to 0.14GPa, and the single crystal graphite sheet layer can be really stripped; 2) When the diameter of the medium is 0.4-1.0mm, the centrifugal friction strength is in the range of 0.2MPa-7GPa, and graphite sheets which are likely to peel off and have very obvious attenuation of Van der Waals acting force exist.
Therefore, the centrifugal peeling device in the invention has the following advantages: the friction strength of the medium in centrifugal motion is uniform. 3. Comparison of experiments
3.1 conditions of the experiment
1) Centrifugation medium: the diameter of the zirconium balls is in mm, and the diameter is from 0.3mm to 1.0mm.
2) Raw materials for peeling single-layer/few-layer graphene: (1) The particle size is 50-100 mesh expanded graphite, preferably 80 mesh, and the expansion ratio is 200-600 times, preferably 400 times. (2) The solvent is one or a combination of N-methyl pyrrolidone NMP, ethanol, isopropanol and water. (3) Dispersing agent polyvinylpyrrolidone PVP and its modified copolymer, polyvinylidene fluoride and its modified copolymer, polyacrylic acid and its modified copolymer.
3) Our designed centrifugal exfoliation apparatus: diameter 234mm in the cavity, medium (zirconium beads) filling mass 75kg, centrifuge revolution: 500-3000rpm (revolutions per minute), preferably 1350rpm, and the temperature in the cavity does not exceed 70 ℃ during centrifugal stripping.
The comparison experiment adopts ordinary 25CE stick round pin mill, and zirconium pearl filling mass is 75kg, and internal diameter 234mm grinds the revolution: 500-1800rpm (rotation per minute), preferably 1350rpm, and the temperature in the cavity does not exceed 70 ℃ during grinding.
3.2 Material proportioning
Materials to be processed: mixing expanded graphite, dispersant and solvent to obtain a mixed solution with a certain solid content, and stirring in a pre-dispersing tank (0.5-1 h/100 kg).
3.3 centrifugal peeling
Pumping the material to be processed into a centrifugal stripping device or a 25CE pin grinder, controlling a certain revolution, carrying out low speed and high speed, carrying out centrifugal motion on the material to be processed and a medium in a cavity of the centrifugal stripping device or the 25CE pin grinder, and circulating the material to be processed and a pre-dispersing tank back and forth in the cavity of the centrifugal stripping device and the pre-dispersing tank (1.5-3 h/100 kg).
3.4 evaluation
And (3) obtaining a uniformly dispersed dispersion after centrifugal stripping, mainly testing the solid content, viscosity CPS and conductivity of the dispersion, coating the dispersion on an aluminum foil, drying, and testing a scanning electron microscope and the like.
1) Dispersion liquid solid content = (expanded graphite weight + dispersant weight)/(expanded graphite weight + dispersant weight + solvent weight).
2) Viscosity: one cup of the dispersion was taken from a 50ml beaker and placed under the viscometer, the test spindle (spindle # 4) was adjusted at 30rpm and the viscosity was recorded and averaged over three points.
3) Mixing with lithium iron phosphate.
The weight of the lithium iron phosphate material, carbon black, single layer/few layer graphene dispersion (NMP system), PVDF, and NMP (N-methylpyrrolidone) was first weighed. The material ratio is lithium iron phosphate: carbon black: few-layer graphene: PVDF = 97.5. The solid content of a mixed material of the lithium iron phosphate material and the PVDF (lithium iron phosphate + carbon black + few-layer graphene + PVDF)/(lithium iron phosphate + carbon black + few-layer graphene + PVDF + NMP) =52%.
A material mixing step: firstly, putting a certain amount of NMP solution into a 50mL volumetric flask, starting magnetic stirring, and then adding a certain amount of PVDF; after dissolving, adding a certain amount of few-layer graphene dispersion liquid; stirring for about 30min, and adding a certain amount of lithium iron phosphate; then continuously stirring the mixture for 12 hours on a magnetic stirrer to obtain the evenly mixed paste.
Drying the paste: and (3) baking the uniformly mixed paste in a vacuum oven at 120 ℃ for 3h, closing the oven, naturally cooling to room temperature, and grinding to obtain powder.
4) And (6) testing the conductivity. The powder is filled into a powder cavity of a four-probe tester, tabletting is carried out under the action of 15MPa, the conductivity value of the powder is tested by using a four-probe, and the average value of three points is taken.
5) And (5) carrying out scanning electron microscope SEM test. Coating the dispersion after centrifugal stripping on an aluminum foil, baking for 1h in a vacuum oven at 120 ℃, cutting into 1 × 1cm small blocks, placing on an SEM material platform, collecting secondary electrons excited during sample surface scanning through a detector, and observing the microstructure of the sample.
6) And (4) carrying out TEM test on a projection electron microscope. And (3) placing 1ml of the dispersion after centrifugal stripping in 50ml of ethanol, ultrasonically dispersing for 1h, sampling by using a dropper, dripping on a copper mesh carrier, and observing the microstructure of the dispersion under TEM.
3.5 detailed experiments
Experiment 1: taking 2.12kg of graphite powder, 2.67kg of a dispersing agent and 200kg of a solvent (N-methyl pyrrolidone NMP) to stir and disperse in a pre-dispersing tank, conveying the graphite powder to an inner cavity (the diameter is 234mm, 75kg of 0.3mm zirconium beads are filled in the inner cavity) of a centrifugal stripping device at a certain speed controlled by a diaphragm pump, firstly setting 700rpm to start centrifugal motion, then increasing the speed to 1350rpm (the linear speed is 11 m/s), centrifugally moving the material and a medium (zirconium beads) in the centrifugal stripping cavity, connecting the material and the pre-dispersing tank in series for closed loop, circularly moving for 6 hours back and forth, then discharging the product, and carrying out parameter evaluation.
Experiment 2: taking 2.12kg of graphite powder, 2.67kg of a dispersing agent and 200kg of a solvent (N-methyl pyrrolidone NMP) to stir and disperse in a pre-dispersing tank, conveying the graphite powder to an inner cavity (which is straight through 234mm and is filled with 75kg of 0.6mm zirconium beads) of a centrifugal stripping device at a certain speed controlled by a diaphragm pump, firstly setting 700rpm to start centrifugal motion, then increasing the speed to 1350rpm (linear speed of 11 m/s), centrifugally moving the material and a medium (zirconium beads) in the centrifugal stripping cavity, connecting the material and the pre-dispersing tank in series for closed loop, circularly moving the material and the medium (zirconium beads) for 6 hours back and forth, then discharging the product, and carrying out parameter evaluation.
Comparative experiment 1: taking 2.12kg of graphite powder, 2.67kg of a dispersing agent and 200kg of a solvent (N-methyl pyrrolidone NMP), stirring and dispersing in a pre-dispersion tank, conveying to an inner cavity (which is 234mm straight and is filled with 75kg of 0.3mm zirconium beads) of a 25CE pin grinding machine at a certain speed controlled by a diaphragm pump, firstly setting 700rpm to start centrifugal motion, then accelerating to 1350rpm (linear speed is 11 m/s), centrifugally moving the material and a medium (zirconium beads) in a centrifugal stripping cavity, connecting the material and the pre-dispersion tank in series for closed loop, circulating back and forth for 6 hours, then discharging the product, and carrying out parameter evaluation.
Comparative experiment 2: taking 2.12kg of graphite powder, 2.67kg of a dispersing agent and 200kg of a solvent (N-methyl pyrrolidone NMP) to stir and disperse in a pre-dispersing tank, conveying the graphite powder to an inner cavity of a 25CE (straight through 234mm, the inner cavity is filled with 75kg of 0.6mm zirconium beads) pin grinding machine at a certain speed controlled by a diaphragm pump, firstly setting 700rpm to start centrifugal motion, then increasing the speed to 1350rpm (linear speed is 11 m/s), centrifugally moving the material and a medium (zirconium beads) in a centrifugal stripping cavity, connecting the material and the pre-dispersing tank in series for closed loop, circularly moving the material and the medium (zirconium beads) for 6 hours back and forth, then discharging the product, and carrying out parameter evaluation.
Table 2 table of test results of each experimental protocol
FIG. 3 product SEM of experiment 1 centrifugal 0.3mm media and material from centrifugal stripping apparatus
FIG. 4 experiment 1 centrifugal stripping device centrifugal 0.3mm medium and material product TEM
FIG. 5 experiment 2 product SEM of centrifugal 0.6mm media and material from centrifugal peeling device
FIG. 6 product SEM of comparative experiment 1, 25CE pin mill centrifuging 0.3mm media versus material;
FIG. 7 product TEM of comparative experiment 1, 25CE pin mill centrifuged 0.3mm media and material;
figure 8 product SEM of comparative experiment 2, 25CE pin mill centrifuge 0.6mm media and material.
4. Analysis of results
1) Experiment 1, the centrifugal stripping device designed by us is used for centrifuging materials by a medium of 0.3mm to obtain a dispersion liquid with the solid content of 6.01 percent, the viscosity of 2040CPS and the conductivity of 60.3 mS/cm after mixing materials in a lithium iron phosphate material. As can be seen from the SEM of fig. 3, the dispersion had a large number of single-layer or few-layer graphene sheets, which were sufficiently exfoliated. As can be seen from the TEM in fig. 4, the number of graphene sheets in the dispersion was 3 to 5.
2) Experiment 2, the centrifugal stripping apparatus designed by us was used to centrifuge the material with a medium of 0.6mm to obtain a dispersion with a solid content of 6.02%, a viscosity of 1200CPS, and a conductivity of 39.1 mS/cm after mixing in the lithium iron phosphate material.
As can be seen from the SEM in fig. 5, the graphite sheet layer in the dispersion was thick, i.e., 10 or more layers.
3) In comparison with experiment 1, the material was centrifuged in a 0.3mm medium using a 25CE pin mill to obtain a dispersion having a solids content of 6.06%, a viscosity of 1360CPS and a conductivity of 42.8 mS/cm after mixing in a lithium iron phosphate material.
The SEM in FIG. 6 shows that the graphite sheet layer in the dispersion was thick, and the TEM in FIG. 7 shows that the number of graphene sheets in the dispersion was 10 to 20.
4) In comparative experiment 2, the material was centrifuged with a 25CE pin mill in a medium of 0.6mm to obtain a dispersion having a solid content of 6.03%, a viscosity of 870CPS and a conductivity of 34.8mS/cm after mixing in the lithium iron phosphate material.
As can be seen from the SEM in fig. 8, the graphite flakes in the dispersion were thicker, 20 or more.
5) Viscosity comparative analysis: in general, the larger the specific surface area of the carbon material, the higher the viscosity of the dispersion. After the graphite is centrifugally exfoliated, the more the exfoliation is sufficient, i.e., the greater the number of single/few-layer graphene, the greater the specific surface area and the higher the viscosity. The data of the experiments 1 and 2 are compared in comprehensive experiments 1 and 2, and a) shows that the adopted medium is small and the centrifugal peel strength is high; b) Under the condition of the medium with the same diameter, the centrifugal peeling strength of the centrifugal peeling device designed by the inventor is obviously superior to that of a common 25CE pin grinding machine.
6) SEM and TEM comparative analysis of experiment 1 and comparative experiment 1: a) The dispersion liquid of experiment 1 contains a large amount of single-layer or few-layer graphene which is fully peeled off, and the number of the layers is 3-5; b) In the dispersion liquid of experiment 2, the graphite sheet layer is thick, and the number of the graphite sheet layers is 10-20; c) Under the condition of medium with the same diameter, the centrifugal stripping device designed by the inventor can more easily strip dispersed monolayer/few-layer graphene than a common 25CE pin grinding machine.
7) Comparative analysis of the mixture conductivity in lithium iron phosphate (1% sp + 0.5% graphene) revealed: experiment 1 shows that the conductivity of the graphene is 60.3 mS/cm at most, which is obviously superior to that of experiment 2 and compared experiments 1 and 2, and that the single-layer/few-layer graphene obtained in experiment 1 has higher specific surface area, is fully dispersed in lithium iron phosphate, and forms richer conductive grids; the graphite sheet structures which are mainly 10-20 layers and even thicker are obtained in the experiment 2 and the comparative experiments 1 and 2, the conductive network structures in the lithium iron phosphate are relatively few, and the overall conductivity is low.
Finally, it should be noted that the above embodiments are only used for illustrating the technical solutions of the present invention, and not for limiting the protection scope of the present invention, although the present invention is described in detail with reference to the preferred embodiments, it should be understood by those skilled in the art that modifications or equivalent substitutions can be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.
Claims (10)
1. A device for centrifugally stripping single-layer/few-layer graphene dispersion liquid is characterized in that: the device comprises a centrifugal stripping device and a pre-dispersing tank, wherein the centrifugal stripping device is connected with the pre-dispersing tank through a material circulating pipeline;
the centrifugal stripping device comprises a tank body, a rotor is arranged in the tank body, the rotor comprises a central shaft and blades which are arranged on the central shaft and are arranged at equal intervals along the circumferential direction of the central shaft, the central shaft is connected with a first motor, the distance between the outer end parts of the blades and the inner wall of the tank body is 1-3mm, and the diameter of an inner cavity of the tank body is 234 +/-2 mm.
2. The apparatus of claim 1, wherein the apparatus is configured to centrifugally exfoliate the single-layer/few-layer graphene dispersion: and a low-speed stirring device and a high-speed stirring device are arranged in the pre-dispersion tank.
3. The apparatus of claim 1, wherein the apparatus is configured to centrifugally exfoliate the single-layer/few-layer graphene dispersion: and circulating cooling jackets are arranged at the peripheries of the pre-dispersion tank and the centrifugal stripping device.
4. The apparatus of claim 1, wherein the apparatus is configured to centrifugally exfoliate the single-layer/few-layer graphene dispersion: the blades are annular in shape, and the distance between every two adjacent blades is larger than the arc length of each blade.
5. The apparatus of claim 1, wherein the apparatus is configured to centrifugally exfoliate the single-layer/few-layer graphene dispersion: the centrifugal stripping device is filled with a centrifugal medium, the filling amount of the centrifugal medium is 80% of the volume of the cavity, and the diameter of the centrifugal medium is 0.3-1.0mm.
6. The centrifugal exfoliation method of an apparatus for centrifugally exfoliating a single/few-layer graphene dispersion of any one of claims 1-5, wherein: the centrifugal peeling method comprises the following steps:
filling a centrifugal medium in a centrifugal stripping device, adding graphite powder, a dispersing agent and a solvent in a pre-dispersing device, stirring and dispersing, conveying the materials into the centrifugal stripping device through a circulating pipeline, setting centrifugal stripping parameters, carrying out centrifugal motion on the materials and the medium in a centrifugal stripping cavity, connecting the materials and the medium with the pre-dispersing tank in series for closed loop, carrying out circulating motion for 6 +/-0.5 h, and then discharging the products for parameter evaluation.
7. The centrifugal peeling method according to claim 6, characterized in that: the centrifugal speed is 500-3000rpm in the centrifugal parameters, the speed is low firstly and then the speed is high, and the temperature in the cavity is not more than 70 ℃ in the centrifugal stripping process.
8. The centrifugal peeling method according to claim 6, characterized in that: the particle size of the graphite powder is 50-100 meshes, and the expansion ratio is 200-600 times.
9. The centrifugal peeling method according to claim 6, characterized in that: the solvent is one or a combination of more of N-methyl pyrrolidone NMP, ethanol, isopropanol and water; dispersing agent polyvinylpyrrolidone PVP and its modified copolymer, polyvinylidene fluoride and its modified copolymer, polyacrylic acid and its modified copolymer.
10. The centrifugal peeling method according to claim 6, characterized in that: the mass ratio of the graphite powder to the dispersing agent is 1.26.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN116812560A (en) * | 2023-08-31 | 2023-09-29 | 江苏希诚新材料科技有限公司 | Pneumatic conveying device for carbon nano powder |
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| CN109095462A (en) * | 2018-07-26 | 2018-12-28 | 北京旭碳新材料科技有限公司 | A kind of graphene and its preparation method and application |
| CN114479546A (en) * | 2021-11-08 | 2022-05-13 | 浙江省海洋开发研究院 | Preparation method and application of easily-dispersible graphene slurry |
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| CN106865530A (en) * | 2016-12-23 | 2017-06-20 | 成都新柯力化工科技有限公司 | A kind of method that stripping prepares the high-speed mixer of Graphene and its peels off Graphene |
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