CN112429726A - 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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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 150
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 121
- 239000006185 dispersion Substances 0.000 title claims abstract description 103
- 239000007788 liquid Substances 0.000 title claims abstract description 74
- 238000002360 preparation method Methods 0.000 title claims abstract description 18
- 239000002270 dispersing agent Substances 0.000 claims abstract description 68
- 238000000034 method Methods 0.000 claims abstract description 17
- 229910002804 graphite Inorganic materials 0.000 claims description 31
- 239000010439 graphite Substances 0.000 claims description 31
- 239000000243 solution Substances 0.000 claims description 16
- 238000003756 stirring Methods 0.000 claims description 13
- 239000011259 mixed solution Substances 0.000 claims description 12
- 239000002245 particle Substances 0.000 claims description 11
- 239000002904 solvent Substances 0.000 claims description 9
- 239000002002 slurry Substances 0.000 claims description 8
- 239000006258 conductive agent Substances 0.000 claims description 6
- 239000000203 mixture Substances 0.000 claims description 5
- 229920000642 polymer Polymers 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 3
- 239000002131 composite material Substances 0.000 claims 1
- 239000002064 nanoplatelet Substances 0.000 abstract description 7
- 239000004094 surface-active agent Substances 0.000 abstract description 4
- 230000009286 beneficial effect Effects 0.000 abstract description 3
- 230000002195 synergetic effect Effects 0.000 abstract description 2
- 230000000052 comparative effect Effects 0.000 description 11
- 239000000463 material Substances 0.000 description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 9
- 239000008367 deionised water Substances 0.000 description 8
- 229910021641 deionized water Inorganic materials 0.000 description 8
- 230000000694 effects Effects 0.000 description 8
- 238000002156 mixing Methods 0.000 description 8
- 239000007787 solid Substances 0.000 description 8
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 6
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- WHNWPMSKXPGLAX-UHFFFAOYSA-N N-Vinyl-2-pyrrolidone Chemical compound C=CN1CCCC1=O WHNWPMSKXPGLAX-UHFFFAOYSA-N 0.000 description 5
- 229920003081 Povidone K 30 Polymers 0.000 description 5
- 229920003082 Povidone K 90 Polymers 0.000 description 5
- 239000007970 homogeneous dispersion Substances 0.000 description 5
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 description 4
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 239000004372 Polyvinyl alcohol Substances 0.000 description 3
- 238000000265 homogenisation Methods 0.000 description 3
- 229920002451 polyvinyl alcohol Polymers 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- CSCPPACGZOOCGX-UHFFFAOYSA-N Acetone Chemical compound CC(C)=O CSCPPACGZOOCGX-UHFFFAOYSA-N 0.000 description 2
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910021383 artificial graphite Inorganic materials 0.000 description 2
- 239000011230 binding agent Substances 0.000 description 2
- 238000010586 diagram Methods 0.000 description 2
- 238000001035 drying Methods 0.000 description 2
- 238000005485 electric heating Methods 0.000 description 2
- 239000007770 graphite material Substances 0.000 description 2
- 238000000227 grinding Methods 0.000 description 2
- 238000009776 industrial production Methods 0.000 description 2
- 239000010410 layer Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 239000002736 nonionic surfactant Substances 0.000 description 2
- 229920000139 polyethylene terephthalate Polymers 0.000 description 2
- 239000005020 polyethylene terephthalate Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 229920000036 polyvinylpyrrolidone Polymers 0.000 description 2
- 239000001267 polyvinylpyrrolidone Substances 0.000 description 2
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 description 2
- 238000001179 sorption measurement Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 229910010584 LiFeO2 Inorganic materials 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- 238000005411 Van der Waals force Methods 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000012752 auxiliary agent Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 125000004432 carbon atom Chemical group C* 0.000 description 1
- 239000004020 conductor Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007423 decrease Effects 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 238000004299 exfoliation Methods 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 239000011229 interlayer Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000002135 nanosheet Substances 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- -1 polyethylene terephthalate Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 239000000523 sample Substances 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 238000000527 sonication Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- YNHJECZULSZAQK-UHFFFAOYSA-N tetraphenylporphyrin Chemical compound C1=CC(C(=C2C=CC(N2)=C(C=2C=CC=CC=2)C=2C=CC(N=2)=C(C=2C=CC=CC=2)C2=CC=C3N2)C=2C=CC=CC=2)=NC1=C3C1=CC=CC=C1 YNHJECZULSZAQK-UHFFFAOYSA-N 0.000 description 1
- 238000009736 wetting Methods 0.000 description 1
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- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/15—Nano-sized carbon materials
- C01B32/182—Graphene
- C01B32/184—Preparation
- C01B32/19—Preparation by exfoliation
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01B—CABLES; CONDUCTORS; INSULATORS; SELECTION OF MATERIALS FOR THEIR CONDUCTIVE, INSULATING OR DIELECTRIC PROPERTIES
- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
- H01B1/04—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors mainly consisting of carbon-silicon compounds, carbon or silicon
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
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- H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
- H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
- H05B3/00—Ohmic-resistance heating
- H05B3/10—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor
- H05B3/12—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material
- H05B3/14—Heating elements characterised by the composition or nature of the materials or by the arrangement of the conductor characterised by the composition or nature of the conductive material the material being non-metallic
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- C01B2204/28—Solid content in solvents
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Abstract
The invention provides a graphene dispersion liquid and a preparation method and application thereof. The method has the advantages that the size and the number of the graphene nanoplatelets are changed along with the change of the size and the number of the graphene nanoplatelets in the physical stripping process to match with a proper molecular weight dispersing agent, so that the use amount of the dispersing agent can be reduced while the high-efficiency stripping is realized; secondly, the graphene dispersion liquid prepared by the invention contains low molecular weight and high molecular weight surfactants which have synergistic effect and are beneficial to stable dispersion of graphene; finally, the dispersing agent is added in batches, so that the damage of multiple times of pre-dispersing treatment on the structure of the high-molecular dispersing agent is avoided, and the controllability of the technological process is improved.
Description
Technical Field
The invention belongs to the technical field of conductive materials, and particularly relates to a graphene dispersion liquid and a preparation method and application thereof.
Background
Graphene is a polymer made of carbon atoms in sp2The hybrid tracks form a hexagonal honeycomb lattice two-dimensional carbon nanomaterial. Due to the uniqueness of the structure, the graphene has the characteristics of high electric conductivity, high heat conductivity, high strength, high specific surface and the like. The physical stripping preparation method can prepare the high-electric-conductivity and heat-conduction graphene material without damaging the graphite lamellar structure, has a simple process, is easy for industrial production, and is more and more concerned by the industrial industry. However, two key problems need to be solved in the process of preparing graphene dispersion liquid by physical stripping, namely, on one hand, the solution fully infiltrates the surface of the graphite material to facilitate the stripping effect of mechanical force on the graphite material, and on the other hand, the stripped graphene is stabilized to prevent the graphene from being stacked again. The nonionic surfactant is easily adsorbed to the surface of the graphite flake to soak and strip graphite, and when the molecular chain of the nonionic dispersant is long enough and fully extended, the steric hindrance of the graphene flake causes the interlayer spacing to be far greater than the distance generated by van der Waals force, so that the graphene is dispersed, and the graphene dispersing agent is an excellent dispersing agent material in the process of preparing graphene dispersing liquid by physical stripping. It should be noted that, during the preparation of graphene dispersion liquid by physical exfoliation, the graphene sheet layers become thinner, the number of graphene sheets increases, and the sheet diameter decreases, so the demand for matching dispersant systems also changes. Currently, in order to achieve better peeling and dispersing effects, it is generally necessary to add a higher concentration of dispersant. For example, CN111129470A takes polyvinylpyrrolidone and/or tetraphenylporphyrin as dispersant to physically strip and prepare high-solid content graphene dispersion liquid, although the solid content of graphene can reach 10-15%, a large amount of dispersant is added (the dispersant accounts for more than 20% of the total solid content). Too much dispersant dosage can not only increase the cost, but also introduce too many impurities in downstream application, which affects the application performance of the graphene dispersion liquid. For example, as lithiumWhen the conductive agent material of the ion battery is used, the specific capacity and the cycling stability of the lithium ion battery can be influenced by excessive dispersant.
Researches show that the dispersing effects of different molecular weight high molecular weight nonionic surfactants on graphene nanoplatelets are different. Namely, if the molecular weight of the dispersant is small, the adsorption effect is relatively weak, the adsorption amount is relatively small, the steric hindrance effect is limited, and relatively poor dispersion stability is shown; if the molecular weight of the dispersant is too large, a plurality of graphene nanosheets are adsorbed on the same molecular chain, and the dispersion stability of the graphene is also affected.
Disclosure of Invention
The invention aims to overcome the problems in the prior art and provides a graphene dispersion liquid and a preparation method and application thereof.
The technical scheme adopted by the invention is as follows:
in a first aspect of the present invention, there is provided:
a graphene dispersion liquid comprises graphene, a dispersing agent and a solvent, wherein the dispersing agent comprises a high molecular weight dispersing agent and a low molecular weight dispersing agent.
Preferably, the graphene dispersion liquid comprises, by mass, 5-10 parts of the graphene, 0.5-1 part of the dispersant and 89-95 parts of the solvent.
Preferably, the mass ratio of the high molecular weight dispersant to the low molecular weight dispersant is (1-4): (6-9).
Preferably, the high molecular weight is an average molecular weight of 10 to 40 ten thousand, and the low molecular weight is an average molecular weight of 1 to 10 ten thousand.
Preferably, the high molecular weight is 15 to 40 ten thousand in average molecular weight, and the low molecular weight is 1 to 6 ten thousand in average molecular weight.
Preferably, the dispersant is one or more of nonionic polymer dispersants.
Preferably, the dispersant is at least one selected from the group consisting of polyvinylpyrrolidone, polyvinyl alcohol, and polyethylene glycol.
Preferably, the graphite is at least one selected from the group consisting of flake graphite, artificial graphite, expanded graphite, and expandable graphite.
Preferably, the solvent is at least one selected from the group consisting of water, ethanol, acetone, N-methylpyrrolidone (NMP), and N, N-Dimethylformamide (DMF).
In a second aspect of the present invention, there is provided:
a preparation method of a graphene dispersion liquid comprises the following steps:
(1) dispersing a high molecular weight dispersant and a low molecular weight dispersant into a solvent respectively to obtain a mixed solution A and a mixed solution B correspondingly;
(2) stirring graphite, adding the graphite into the mixed solution A, and performing pre-dispersion to obtain a pre-dispersion solution;
(3) and adding the mixed solution B into the pre-dispersion solution, and continuously performing pre-dispersion to obtain the graphene dispersion solution with the composition.
Preferably, the volume ratio of the mixed solution a to the mixed solution B is (7-9): (1-3).
Preferably, the particle size D50 of the graphite in the step (2) is 20-100 microns.
Preferably, the graphite is at least one selected from the group consisting of flake graphite, artificial graphite, expanded graphite, and expandable graphite.
Preferably, the particle size D50 of the graphene in the pre-dispersion liquid is 5-20 microns.
Preferably, the pre-dispersion is at least one selected from the group consisting of sonication, sanding and homogenization.
Preferably, the power of the ultrasonic wave is 600W to 3000W, and the time of the ultrasonic wave is 1h to 20 h.
Preferably, the rotational speed of the sanding is 500 rpm-2000 rpm, the temperature of the sanding is 25-50 ℃, and the time of the sanding is 0.5-5 h.
Preferably, the homogenization pressure is 50 to 200MPa, and the homogenization frequency is 1 to 20 times.
In a third aspect of the present invention, there is provided:
the application of the graphene dispersion liquid in a conductive agent and/or a battery and/or an electric heating slurry is disclosed, wherein the graphene dispersion liquid is the graphene dispersion liquid or is prepared by the preparation method of the graphene dispersion liquid.
The invention has the beneficial effects that:
(1) dispersing agents with different molecular weights are added according to the change of the particle size and the number of the graphene in the graphite stripping and dispersing process, so that the solvent fully wets the graphite surface, and the stripping and the dispersing of the graphene in the pre-dispersing process are facilitated.
(2) The graphite has large sheet diameter and small quantity at the beginning, a small amount of high molecular weight surfactant can be used for adsorbing and wetting the graphite, and the ultrahigh steric hindrance of the high molecular weight surfactant is favorable for uniform dispersion of the graphite. With the pre-dispersion treatment, the graphite is gradually stripped into graphene micro-sheets, the sheet diameter and the thickness are reduced, and the number of the graphene micro-sheets is greatly increased, which is shown as the viscosity of the material is increased. At the moment, a small amount of low-molecular-weight dispersing agent is introduced, so that the material can be completely wetted, the viscosity of the system is obviously reduced, and the material is continuously subjected to pre-dispersion stripping to form a stable graphene dispersion liquid. The method has the advantages that the size and the number of the graphene nanoplatelets are changed along with the change of the size and the number of the graphene nanoplatelets in the physical stripping process to match with a proper molecular weight dispersing agent, so that the use amount of the dispersing agent can be reduced while the high-efficiency stripping is realized; secondly, the graphene dispersion liquid prepared by the invention contains low molecular weight and high molecular weight surfactants which have synergistic effect and are beneficial to stable dispersion of graphene; finally, the dispersing agent is added in batches, so that the damage of multiple times of pre-dispersing treatment on the structure of the high-molecular dispersing agent is avoided, and the controllability of the technological process is improved.
(3) According to the invention, the high-solid content graphene dispersion liquid can be uniformly dispersed under the condition of lower dispersant dosage, the dispersant accounts for less than 8% of the total solid content, and the proportion of the dispersant is obviously reduced compared with that of 15-50% of the dispersant in the current market; the less dispersant consumption not only reduces the cost, but also reduces the influence of the dispersant on the performance of the product at the application end, for example, the mass of the dispersant which can not store energy is reduced in the lithium ion battery, and the mass specific capacitance of the lithium ion battery can be improved; in the electrothermal slurry, the influence of a dispersant material on the lapping effect of the graphene conductive agent material is reduced, so that higher conductivity is represented.
(4) The invention only needs to add dispersants with different molecular weights in the pre-dispersion process, has simple process and is suitable for industrial production.
Drawings
FIG. 1 is a schematic diagram of a pre-dispersion process of a graphene dispersion according to the present invention; 1-graphite, 2-high molecular weight dispersant, 3-graphene microchip aggregate, 4-graphene microchip and 5-low molecular weight dispersant.
Fig. 2 is a Scanning Electron Microscope (SEM) image of the graphene dispersion prepared in example 1.
FIG. 3 is an X-ray diffraction (XRD) spectrum of the graphene dispersion of example 1 and comparative examples 1-2.
FIG. 4 shows graphene dispersions of example 3 and comparative example 3 as conductive agents for LiFeO2Rate characteristic curve of lithium ion battery.
Detailed Description
In order to make the objects, technical solutions and technical effects of the present invention more clear, the present invention will be described in further detail with reference to specific embodiments. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention.
In the preparation process of the graphene dispersion liquid, a schematic diagram of a pre-dispersion process is shown in fig. 1.
In the following examples or comparative examples, the contents of the respective substances were calculated in the following manner:
the total content of the dispersing agent in the graphene dispersion liquid is equal to the total mass of the dispersing agent/the mass of the graphene dispersion liquid;
the content of graphene in the graphene dispersion liquid is equal to the mass of graphene/the mass of the graphene dispersion liquid;
the dispersant in the graphene dispersion liquid accounts for the total mass of the dispersant/(the total mass of the dispersant + the mass of graphene)
Example 1: a graphene dispersion liquid and a preparation method thereof are as follows:
dispersing 1g of PVP-K90(MW 360000) into 643g of deionized water, adding 80g of expanded graphite with the particle size D50 of 50 mu m, mechanically stirring and uniformly mixing, and then carrying out high-pressure homogeneous dispersion for 2 times under the pressure of 100Mpa to obtain a pre-dispersion liquid; and adding 276g of deionized water solution containing 3g of PVP-K30(MW 40000) into the pre-dispersion liquid, uniformly stirring, and uniformly dispersing for 3 times to obtain a uniformly and stably dispersed graphene dispersion liquid.
The total content of the dispersing agent in the graphene dispersion liquid is 0.4%, the content of the graphene is 8%, and the dispersing agent accounts for 4.7% of the total solid content; the SEM spectrogram is shown in figure 2, the graphene nanoplatelets are uniformly dispersed, and no obvious stacking phenomenon is found.
Example 2: a graphene dispersion liquid and a preparation method thereof are as follows:
dispersing 1.2g of polyvinyl alcohol (MW 180000) into 808.8g of deionized water, adding 90g of expanded graphite with the particle size D50 of 20 microns, mechanically stirring and uniformly mixing, and then sanding for 30min at 1500rpm by using a sand mill to obtain a dispersion liquid; 90g of deionized water solution containing 4.8g of polyvinyl alcohol (MW 20000) is added into the pre-dispersion liquid, and after uniform stirring, sanding is carried out for 1h, so as to obtain uniform and stable dispersion graphene dispersion liquid.
The content of the dispersing agent in the graphene dispersion liquid is 0.6%, the content of the graphene is 10%, and the dispersing agent accounts for 5.6% of the total solid content.
Example 3: a graphene dispersion liquid and a preparation method thereof are as follows:
dispersing 2g PVP-K90(MW 360000) into 750g N-methyl pyrrolidone solution, adding 60g expanded graphite with the particle size D50 of 30 mu m, mechanically stirring and uniformly mixing, and then sanding for 1h at the rotating speed of 1000rpm by using a sand mill to obtain a dispersion liquid; and adding 188g of N-methyl pyrrolidone solution containing 3g of PVP-K30(MW 40000) into the pre-dispersion liquid, stirring uniformly, and sanding for 2h to obtain the uniformly and stably dispersed graphene dispersion liquid.
The content of the dispersing agent in the graphene dispersion liquid is 0.5%, the content of the graphene is 6%, and the dispersing agent accounts for 7.6% of the total solid content.
Comparative example 1: a graphene dispersion liquid and a preparation method thereof are as follows:
dispersing 1g of PVP-K90(MW 40000) into 643g of deionized water, adding 80g of expanded graphite with the particle size D50 of 50 microns, mechanically stirring and uniformly mixing, and then carrying out high-pressure homogeneous dispersion for 2 times under the pressure of 100MPa to obtain a pre-dispersion liquid; 276g of deionized water solution containing 3g of PVP-K90(MW 360000) is added into the pre-dispersion liquid, and the graphene dispersion liquid is obtained after the uniform stirring and the homogeneous dispersion for 3 times.
Comparative example 2: a graphene dispersion liquid and a preparation method thereof are as follows:
dispersing 1g of PVP-K30(MW 40000) into 643g of deionized water, adding 80g of expanded graphite with the particle size D50 of 50 microns, mechanically stirring and uniformly mixing, and then carrying out high-pressure homogeneous dispersion for 2 times under the pressure of 100MPa to obtain a pre-dispersion liquid; 276g of deionized water solution containing 3g of PVP-K30(MW 40000) is added into the pre-dispersion liquid, and the graphene dispersion liquid is obtained after the uniform stirring and the 3-time homogeneous dispersion.
The X-ray diffraction (XRD) tests of the graphene dispersions of example 1 and comparative examples 1-2 are respectively performed, and the results are shown in fig. 3, which shows that the diffraction peak intensity of the (002) crystal face of the graphene corresponding to the graphite microcrystalline structure in example 1 is relatively low, which indicates that the number of graphene layers in example 1 is low, and the peeling effect is better.
Comparative example 3: a graphene dispersion liquid and a preparation method thereof are as follows:
dispersing 2g of PVP-K30(MW 40000) into 750g of N-methylpyrrolidone solution, adding 60g of expanded graphite with the particle size D50 of 30 mu m, mechanically stirring and uniformly mixing, and then sanding for 1h at the rotating speed of 1000rpm by using a sand mill to obtain a dispersion liquid; 188g of N-methyl pyrrolidone solution containing 3g of PVP-K90(MW 360000) is added into the pre-dispersion liquid, and after the mixture is uniformly stirred, the mixture is ground for 2 hours to obtain graphene dispersion liquid.
Application example 1:
mixing the graphene dispersion liquid prepared in the examples 1-2 and the comparative examples 1-2, conductive carbon black, a binder and an auxiliary agent according to a certain proportion, grinding by a three-roll mill, and sieving to obtain the graphene electric heating slurry. And then coating the graphene electrothermal slurry on a polyethylene terephthalate (PET) film, drying, and testing the resistivity of the material by using a four-probe tester.
Table 1 graphene electro-thermal paste formulation and resistivity test
The data in Table 1 show that the coating resistivity of the graphene electrothermal slurry prepared by the graphene dispersion liquid prepared in the embodiments 1-2 of the invention can be reduced by about one order of magnitude compared with the coating resistivity of the graphene electrothermal slurry prepared in the comparative examples 1-2. The invention is shown to realize high-efficiency stripping by matching with a proper molecular weight dispersant according to the change of the size and the number of the graphene nanoplatelets in the physical stripping process, and can realize uniform dispersion when being applied to the graphene electrothermal slurry, thereby showing higher conductivity.
Application example 2:
the graphene dispersions (graphene content 6%) prepared in example 3 and comparative example 3 were mixed with conductive carbon black, lithium iron phosphate (LiFeO)2) Powder, binder polyvinylidene fluoride (PVDF), solvent NMP according to 33.3: 2: 32: 4: 28.7 mixing, grinding in vacuum, coating on aluminum foil, and drying to obtain electrode; and then, a lithium ion battery is assembled by taking the metal lithium sheet as a negative electrode to carry out electrochemical test. The results are shown in FIG. 4.
It can be seen that the graphene dispersion liquid in example 3 used as a conductive agent for a lithium ion battery shows higher rate characteristics compared with the graphene dispersion liquid in comparative example 3, which indicates that the graphene dispersion liquid in example 3 of the present invention can be uniformly dispersed in a lithium battery electrode to form a three-dimensional network structure, and shows ideal conductivity.
The above embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above embodiments, and any other changes, modifications, substitutions, combinations, and simplifications which do not depart from the spirit and principle of the present invention should be construed as equivalents thereof, and all such changes, modifications, substitutions, combinations, and simplifications are intended to be included in the scope of the present invention.
Claims (10)
1. A graphene dispersion, characterized in that: the graphene/graphene composite material comprises graphene, a dispersing agent and a solvent, wherein the dispersing agent comprises a high molecular weight dispersing agent and a low molecular weight dispersing agent.
2. The graphene dispersion liquid according to claim 1, wherein: the graphene dispersion liquid comprises, by mass, 5-10 parts of graphene, 0.5-1 part of a dispersing agent and 89-95 parts of a solvent.
3. The graphene dispersion liquid according to claim 1, wherein: the mass ratio of the high molecular weight dispersant to the low molecular weight dispersant is (1-4): (6-9).
4. The graphene dispersion liquid according to claim 1 or 3, wherein: the high molecular weight is 10-40 ten thousand of average molecular weight, and the low molecular weight is 1-10 ten thousand of average molecular weight.
5. The graphene dispersion liquid according to claim 1 or 2, characterized in that: the dispersant is one or more of nonionic polymer dispersants.
6. A preparation method of graphene dispersion liquid is characterized by comprising the following steps: the method comprises the following steps:
(1) dispersing a high molecular weight dispersant and a low molecular weight dispersant into a solvent respectively to obtain a mixed solution A and a mixed solution B correspondingly;
(2) stirring graphite, adding the graphite into the mixed solution A, and performing pre-dispersion to obtain a pre-dispersion solution;
(3) adding the mixed solution B into the pre-dispersion solution, and continuously performing pre-dispersion to obtain the graphene dispersion solution with the composition of any one of claims 1-5.
7. The method for producing a graphene dispersion liquid according to claim 6, characterized in that: the volume ratio of the mixed solution A to the mixed solution B is (7-9): (1-3).
8. The method for producing a graphene dispersion liquid according to claim 6, characterized in that: the particle size D50 of the graphite in the step (2) is 20-100 microns.
9. The method for producing a graphene dispersion liquid according to claim 6, characterized in that: the particle size D50 of graphene in the pre-dispersion liquid is 5-20 microns.
10. The application of the graphene dispersion liquid in a conductive agent and/or a battery and/or an electrothermal slurry is characterized in that: the graphene dispersion liquid is the graphene dispersion liquid as defined in any one of claims 1 to 5, or is prepared by the preparation method of the graphene dispersion liquid as defined in any one of claims 6 to 9.
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