CN107706399B - One-dimensional carbon fiber/carbon nanotube composite material, preparation method and application thereof - Google Patents
One-dimensional carbon fiber/carbon nanotube composite material, preparation method and application thereof Download PDFInfo
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Abstract
The invention relates to a one-dimensional carbon fiber/carbon nanotube composite material, a preparation method and application thereof. The method comprises the steps of carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on conductive slurry in sequence, wherein the conductive slurry is mixed slurry of carbon fibers and carbon nanotubes, or slurry of the carbon fibers or slurry of the carbon nanotubes. The method of the invention can solve the problem that the carbon nano tube and the carbon fiber are easy to agglomerate, obtain the one-dimensional carbon fiber/carbon nano tube composite material with good dispersity and stability, improve the strength of the carbon fiber, improve the antistatic property and improve the safety performance of the prepared battery, and the lithium battery prepared by adopting the one-dimensional carbon fiber/carbon nano tube composite material can greatly improve the rate capability of the lithium battery, and the 30C capacity reaches more than 76.4 percent of 1C capacity.
Description
Technical Field
The invention belongs to the field of new energy materials such as lithium batteries and the like, relates to a carbon fiber/carbon nanotube composite material, a preparation method and application thereof, and particularly relates to a one-dimensional carbon fiber/carbon nanotube composite material, a preparation method and application thereof in a lithium ion battery.
Background
Carbon fibers are one-dimensional carbon materials and have been used as negative electrode materials in early lithium batteries, but natural graphite and artificial graphite, which are spherical in shape, are gradually substituted for the carbon fibers because of low ion mobility in the longitudinal direction and poor rate capability.
In recent years, the conductivity of lithium batteries has been improved by various methods, and the lithium batteries are expected to be well used. CN 104779378A provides a preparation method of a germanium-mesoporous carbon fiber composite lithium battery cathode material, which comprises the steps of preparing mixed solutions of LN and PAN with different proportions, obtaining LN/PAN composite fibers by adopting electrostatic spinning, and placing the LN/PAN composite fibers in a containerEtching in a solvent, and then carrying out preoxidation and carbonization treatment to obtain carbon fibers with special mesoporous structures; finally, the prepared carbon fiber with the mesoporous structure and GeCl4Compounding, in a tube furnace N2/H2The Ge @ MCF composite material is prepared by calcining in a mixed atmosphere, the obtained composite material is used as a nano reactor to prepare the mesoporous carbon fiber composite germanium electrode material, and the confinement effect of the mesoporous carbon fiber is utilized to be applied to a lithium battery, so that the composite germanium electrode material has good cycling stability and higher specific capacity. CN 102668194B provides a cathode active material precursor and an active material for a rechargeable lithium battery including hollow filamentous nanocarbon, and a method of manufacturing the same. The cathode active material precursor for a rechargeable lithium battery, the invention of which comprises hollow filamentous nanocarbons, is a composite cathode active material precursor for a rechargeable lithium battery.
However, the above invention has limited improvement on the ion conductivity of the carbon fiber, and limited improvement on the rate capability when applied to a lithium battery, and is difficult to meet the requirements of practical application, so that it is necessary to provide a one-dimensional carbon composite material with high ion conductivity and excellent strength to improve the rate capability of the lithium battery, thereby meeting the requirements of practical application.
Disclosure of Invention
Aiming at the problems in the prior art, the invention aims to provide a one-dimensional carbon fiber/carbon nanotube composite material, a preparation method thereof and application thereof in a lithium ion battery, the method can well solve the problem that carbon fibers and carbon nanotubes are difficult to disperse in solid, not only can fully play the excellent conductivity of the carbon nanotubes, but also can improve the strength of the carbon fibers, prevent static electricity and improve the practicability and safety of the carbon fibers applied to the battery, and the lithium battery prepared from the one-dimensional carbon fiber/carbon nanotube composite material can greatly improve the rate capability of the lithium battery, and the 30C capacity is more than 76.4% of 1C capacity.
The one-dimensional carbon fiber/carbon nanotube composite material of the invention refers to: the carbon fiber/carbon nanotube composite material is a one-dimensional structure.
In order to achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a preparation method of a one-dimensional carbon fiber/carbon nanotube composite material, which comprises the steps of carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on conductive slurry in sequence;
the conductive slurry may be a mixed slurry of carbon fibers and carbon nanotubes, a slurry of carbon fibers, or a slurry of carbon nanotubes, and is preferably a mixed slurry of carbon fibers and carbon nanotubes.
As a preferred embodiment of the method of the present invention, the solid content of the conductive paste is 1% to 20%, for example, 1%, 3%, 5%, 7%, 9%, 10%, 12%, 15%, 17%, 18.5%, or 20%.
Preferably, the conductive paste is a mixed paste of carbon fibers and carbon nanotubes, and the mass ratio of the carbon nanotubes to the carbon fibers in the mixed paste is 0.1:99.9-10:90, such as 0.1:99.9, 0.3:99.7, 0.5:99.5, 0.8:99.2, 1:99, 1.3:98.7, 1.5:98.5, 2:98, 2.5:97.5, 3:97, 3.6:96.4, 4:96, 4.5:95.5, 5:95, 5.5:94.5, 6:94, 7:93, 7.5:92.5, 8:92, 9:91, 10:90, or the like.
Preferably, the low energy ball milling is ball milling at a rotational speed of 10Hz to 70Hz, such as 10Hz, 15Hz, 20Hz, 22Hz, 25Hz, 30Hz, 40Hz, 45Hz, 50Hz, 55Hz, 60Hz, 65Hz, or 70Hz, etc.
Preferably, the time of the low energy ball milling is 0.5h to 20h, such as 0.5h, 1h, 2h, 2.5h, 3h, 4h, 5h, 5.5h, 6h, 7h, 9h, 10h, 12h, 14h, 15h, 17h, 18h or 20h, and the like.
Preferably, the milling balls used during the low energy ball milling have a size of 5mm to 10mm, such as 5mm, 5.5mm, 6mm, 6.2mm, 6.5mm, 7mm, 7.5mm, 8mm, 8.5mm, 9mm, or 10mm, etc.
Preferably, the milling balls used in the low energy ball milling process are zirconium balls and/or ceramic balls, but are not limited to the above-listed milling balls, and other milling balls commonly used in the art can also be used in the present invention.
Preferably, the equipment adopted by the low-energy ball mill is an attritor mill.
Preferably, the shear dispersion is: the shearing is carried out at a rotation speed of 1000rpm to 4000rpm, for example, 1000rpm, 1250rpm, 1500rpm, 1600rpm, 1800rpm, 2000rpm, 2200rpm, 2400rpm, 2800rpm, 3000rpm, 3250rpm, 3500rpm, 3700rpm, 3800rpm, 4000rpm, or the like.
Preferably, the time for shear dispersion is 0.1h to 2h, such as 0.1h, 0.5h, 1h, 1.2h, 1.4h, 1.5h, 1.75h, 2h, or the like.
Preferably, the equipment used for shearing dispersion is a high-shear disperser, and the high-shear disperser disclosed by the invention is equipment commonly used in the field, and the specific type of the equipment is not limited.
Preferably, the high energy ball milling is performed at a rotation speed of 700rpm to 1500rpm, for example, 700rpm, 800rpm, 900rpm, 1000rpm, 1150rpm, 1250rpm, 1300rpm, 1400rpm, 1500rpm, or the like.
Preferably, the time of the high energy ball milling is 1h to 10h, such as 1h, 2h, 3h, 3.5h, 4h, 5h, 6h, 6.5h, 7h, 8h, 8.5h, 9h or 10h, etc.
Preferably, the size of the milling balls used in the high energy ball milling process is 0.3mm to 1mm, such as 0.3mm, 0.5mm, 0.7mm, 0.8mm, 0.9mm, or 1mm, etc.
Preferably, the grinding balls used in the high-energy ball milling process are zirconium balls and/or ceramic balls, but are not limited to the above-listed grinding balls, and other grinding balls commonly used in the art can also be used in the present invention.
Preferably, the high-energy nanocrystallization is performed by homogenizing with a high-energy nanocrystallization machine.
Preferably, the pressure during the high-energy nanocrystallization is 10MPa to 50MPa, for example, 10MPa, 15MPa, 18MPa, 20MPa, 22.5MPa, 25MPa, 27MPa, 30MPa, 32MPa, 34MPa, 36MPa, 38MPa, 40MPa, 43MPa, 45MPa, or 50MPa, and the like.
Preferably, the time for high-energy nanocrystallization is 1h to 5h, such as 1h, 2h, 2.2h, 2.3h, 2.4h, 2.5h, 2.6h, 2.8h, 3h, 3.2h, 3.3h, 3.5h, 3.6h, 3.7h, 3.85h, 4h or 5h, and the like.
Preferably, the carbon fibers have a diameter of 1 μm to 100 μm, for example 1 μm, 3 μm, 4.5 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm, 10 μm, 12 μm, 13.5 μm, 15 μm, 17 μm, 18.5 μm, 20 μm, 22 μm, 24 μm, 26.5 μm, 28 μm, 30 μm, 32.5 μm, 35 μm, 37 μm, 40 μm, 42 μm, 45 μm, 48 μm, 50 μm, 55 μm, 60 μm, 65 μm, 70 μm, 80 μm, 84 μm, 88 μm, 92 μm, 95 μm, 100 μm or the like.
Preferably, the carbon fiber has a specific surface area of 1m2/g-100m2G, e.g. 1m2/g、5m2/g、10m2/g、20m2/g、35m2/g、50m2/g、60m2/g、70m2/g、80m2/g、90m2In g or 100m2And/g, etc.
Preferably, the carbon nanotubes have a diameter of 10nm to 100nm, such as 10nm, 20nm, 30nm, 40nm, 50nm, 60nm, 70nm, 75nm, 80nm, 90nm, 100nm, or the like.
Preferably, the carbon nanotube has a specific surface area of 50m2/g-300m2A/g, of, for example, 50m2/g、65m2/g、75m2/g、90m2/g、100m2/g、110m2/g、125m2/g、140m2/g、160m2/g、170m2/g、180m2/g、195m2/g、215m2/g、230m2/g、245m2/g、260m2/g、270m2/g、280m2G or 300m2And/g, etc.
The preparation of the one-dimensional carbon fiber/carbon nanotube composite material is closely related to the shape matching of the carbon fibers and the carbon nanotubes, and comprises the matching of parameters such as the diameter of the carbon fibers, the diameter of the carbon nanotubes and the like.
Preferably, the preparation process of the mixed slurry of carbon fibers and carbon nanotubes is as follows: dispersing carbon fibers and carbon nanotubes into a dispersion liquid composed of an organic high molecular polymer and a solvent to obtain a mixed slurry of the carbon fibers and the carbon nanotubes.
Preferably, there are two ways of dispersing carbon fibers and carbon nanotubes into the dispersion, one being: respectively dispersing carbon fibers and carbon nanotubes into the dispersion liquid; the other is as follows: the carbon fiber and the carbon nano tube are mixed uniformly to obtain mixed powder, and then the mixed powder is dispersed into the dispersion liquid.
Preferably, the preparation process of the slurry of carbon fibers is as follows: carbon fibers are dispersed in a dispersion liquid composed of an organic high molecular polymer and a solvent to obtain a slurry of carbon fibers.
Preferably, the preparation process of the slurry of carbon nanotubes is as follows: the carbon nanotubes are dispersed in a dispersion liquid composed of an organic high molecular polymer and a solvent to obtain a slurry of the carbon nanotubes.
Preferably, in the process of preparing the mixed slurry of carbon fibers and carbon nanotubes, the slurry of carbon fibers, and the slurry of carbon nanotubes, the organic high molecular polymer in the dispersion used independently includes any one or a mixture of at least two of polyvinylpyrrolidone (PVP), Polyvinylidene fluoride (PVDF), Polytetrafluoroethylene (PTFE), Polyvinyl chloride (PVC), Acrylonitrile-Styrene-Butadiene copolymer (Acrylonitrile Butadiene Styrene, ABS), Polyethylene (PE), polypropylene (PP), or Polystyrene (PS).
Preferably, the solvent in the dispersion used in the process of preparing the mixed slurry of carbon fibers and carbon nanotubes, the slurry of carbon fibers, and the slurry of carbon nanotubes independently includes N-methylpyrrolidone (1-Methyl-2-pyrrolidone, NMP), H2Any one or a mixture of at least two of O, methanol or ethanol.
As a preferred technical scheme of the preparation method, the method comprises the following steps:
(1) adding an organic high molecular polymer into a solvent to ensure that the solid content is 0.1-5% to obtain a dispersion liquid;
(2) uniformly mixing the carbon nano tube and the carbon fiber according to the mass ratio of 0.1:99.9-10:90 to obtain mixed powder, and then dispersing the mixed powder into the dispersion liquid obtained in the step (1) to obtain conductive slurry, wherein the solid content of the conductive slurry is 1-20%;
(3) and (3) sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on the conductive slurry obtained in the step (2) to obtain the carbon fiber/carbon nanotube composite material.
As another preferable embodiment of the preparation method of the present invention, the method comprises the steps of:
(A) adding an organic high molecular polymer into a solvent to ensure that the solid content is 0.1-5% to obtain a dispersion liquid;
(B) respectively putting carbon nano tubes and carbon fibers into the dispersion liquid obtained in the step (A) to obtain conductive slurry, wherein the mass ratio of the carbon nano tubes to the carbon fibers in the conductive slurry is 0.1:99.9-10:90, and the solid content of the conductive slurry is 1% -20%;
(C) and (C) sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on the conductive slurry obtained in the step (B) to obtain the carbon fiber/carbon nanotube composite material.
As another preferable technical solution of the preparation method of the present invention, the method comprises the steps of:
(a) adding an organic high molecular polymer into a solvent to ensure that the solid content is 0.1-5% to obtain a dispersion liquid;
(b) dispersing carbon nanotubes into a part of the dispersion liquid obtained in the step (a) to obtain slurry of the carbon nanotubes, and sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization to obtain first slurry;
(c) dispersing carbon fibers into the other part of the dispersion liquid obtained in the step (a) to obtain slurry of the carbon fibers, and sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization to obtain second slurry;
(d) and mixing the first slurry and the second slurry for 0.1-5 h to obtain the carbon fiber/carbon nanotube composite material.
In a second aspect, the present invention provides a one-dimensional carbon fiber/carbon nanotube composite material, which is prepared by the method of the first aspect.
In a third aspect, the present invention provides a use of the one-dimensional carbon fiber/carbon nanotube composite material according to the second aspect for preparing a lithium ion battery.
Compared with the prior art, the invention has the following beneficial effects:
(1) the invention creatively adopts the step design of carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on slurry of the carbon fibers and/or the carbon nanotubes (namely mixed slurry of the carbon fibers and the carbon nanotubes, or slurry of the carbon fibers, or slurry of the carbon nanotubes) in sequence, so that the solid is uniformly dispersed, the dispersibility and stability of the carbon nanotubes and the carbon fibers are improved, the strength of the carbon fibers and the conductivity of the obtained composite material are improved, the function of preventing static electricity is also played, and the safety of preparing the battery is further enhanced.
(2) The one-dimensional carbon fiber/carbon nanotube composite material is prepared by uniformly implanting carbon nanotubes in carbon fibers, so that the excellent conductivity of the carbon nanotubes is fully exerted, the rate capability of the carbon fibers applied to a lithium battery is greatly improved, and the one-dimensional carbon fiber/carbon nanotube composite material shows very good rate capability when applied to the lithium battery under the conditions of increasing consumption and supply shortage of natural graphite resources, can effectively replace the traditional material, and solves the problem of resource shortage.
(3) The lithium battery prepared by the one-dimensional carbon fiber/carbon nanotube composite material can greatly improve the rate capability of the lithium battery, and the 30C capacity reaches more than 76.4 percent of the 1C capacity.
Drawings
FIG. 1 is an SEM image of a one-dimensional carbon fiber/carbon nanotube composite material prepared in example 1 of the present invention;
FIG. 2 is a graph of the rate capability of a battery prepared using the one-dimensional carbon fiber/carbon nanotube composite material of example 1 of the present invention;
fig. 3 is a schematic process flow diagram of a process for preparing a one-dimensional carbon fiber/carbon nanotube composite material according to embodiment 1 of the present invention.
Detailed Description
The technical scheme of the invention is further explained by the specific implementation mode in combination with the attached drawings.
Battery assembly and performance testing:
assembling the battery: the test adopts a half-cell test, and firstly, the ternary material and the nano carbon conductive agent (SP) are put into a vacuum oven and baked for 4 hours at 120 ℃. Weighing an NMP solution containing 5% (by weight) of PVDF, then weighing the one-dimensional carbon fiber/carbon nanotube composite material and the nanocarbon conductive agent, putting the three-component material SP, the one-dimensional carbon fiber/carbon nanotube composite material and PVDF, NMP, in a ratio of 95:1:1.5:2.5:50 (wherein PVDF and the material are in a solid ratio), into a homogenizing box, homogenizing for 10min by a homogenizer, and preparing into a paste. The paste was placed on one side of a copper foil, scraped onto the copper foil with a 200 μm draw bar until the surface was smooth, and then baked in a forced air drying oven at 100 ℃ for 8 h. And tabletting and cutting the baked pole piece into electrode pieces in various shapes (rectangular strip, strip or round and the like), accurately weighing the electrode pieces, putting the electrode pieces into a vacuum drying oven, and baking the electrode pieces for 8 hours at 100 ℃ under a vacuum condition to obtain the positive plate.
In a glove box under argon atmosphere, a lithium sheet is taken as a counter electrode, and the positive electrode sheet and the counter electrode prepared by the steps are mixed with 1mol/L LiPF6The EC (ethylene carbonate)/EMC (ethyl methyl carbonate) (the volume ratio of EDC to EMC is 1:1) solution is used as electrolyte (or other electrolyte with the same performance), and 8 pairs (or more than number) of sealed half batteries conforming to the electrode system are assembled in a glove box.
And (3) performance testing:
the half-cells were tested for electrochemical performance on a cell program tester. Test conditions the battery capacity was tested under rate conditions of 1C, 3C, 5C, 10C, 20C and 30C, respectively.
Example 1
(1) The organic high molecular polymer PVP is added into a solvent NMP to obtain a dispersion liquid with the solid content of 1%.
(2) Mixing Carbon Nano Tube (CNT) powder and Carbon Fiber (CF) powder according to the mass ratio of 0.1:99.9, uniformly dispersing the carbon nano tube powder and the Carbon Fiber (CF) powder to obtain mixed powder, and mixing the mixed powder with the dispersion liquid obtained in the step (1) to ensure that the solid content of the obtained conductive paste is 3%.
(3) And (3) firstly, carrying out low-energy ball milling on the conductive slurry obtained in the step (2), wherein the low-energy ball milling adopts an apparatus of an upright ball mill, the grinding balls are zirconium balls, ceramic balls and the like with the sizes of 5-6 mm, the rotating speed of the low-energy ball milling is 30Hz, and the low-energy ball milling time is 4 h.
(4) Then, the mixture is subjected to shear dispersion, wherein the shear speed is 1500rpm, and the shear dispersion time is 1 h.
(5) And then performing high-energy ball milling, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.3-0.5 mm, the rotating speed of the high-energy ball milling is 1500rpm, and the time of the high-energy ball milling is 8 hours.
(6) Finally, the high-energy nanocrystallization is carried out, the pressure of the high-energy nanocrystallization is 10MPa, and the time of the high-energy nanocrystallization is 3 hours. The solid is uniformly dispersed in the solvent, and uniform and stable slurry of the one-dimensional carbon fiber/carbon nanotube composite material is obtained.
The schematic process flow of the preparation of the one-dimensional carbon fiber/carbon nanotube composite material in this example 1 is shown in fig. 3.
And (3) testing results:
fig. 1 is an SEM image of the one-dimensional carbon fiber/carbon nanotube composite material prepared in example 1 of the present invention, and it can be seen from the image that the diameter of the carbon fiber is 5 μm, the diameter of the carbon nanotube is 100nm, and the carbon nanotube is uniformly dispersed on the surface of the carbon fiber without aggregation.
Fig. 2 is a rate performance diagram of a battery prepared from the one-dimensional carbon fiber/carbon nanotube composite material prepared in example 1 of the present invention, and it can be seen from the diagram that the rate performance of the battery is greatly improved, the 30C capacity reaches 80% of the 1C capacity, and the composite material of the present invention exhibits better rate performance compared with a normal carbon fiber material.
Example 2
(1) Adding the mixture of organic high molecular polymer PVP and PVDF into solvent H2In O, a dispersion having a solids content of 5% was obtained.
(2) And (2) putting the Carbon Nanotubes (CNT) into a part of the dispersion liquid in the step (1) to obtain slurry of the carbon nanotubes with the solid content of 5%.
(3) Firstly, performing low-energy ball milling on the slurry of the carbon nano tube in the step (2), wherein equipment adopted by the low-energy ball milling is an upright ball mill, grinding balls are zirconium balls, ceramic balls and the like with the sizes of 10-20 mm, the rotating speed of the low-energy ball milling is 70Hz, and the low-energy ball milling time is 8 hours; then shearing and dispersing for 1h at the shearing speed of 4000 rpm; then high-energy ball milling is carried out, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.4-0.6 mm, the rotating speed of the high-energy ball milling is 1000rpm, and the time of the high-energy ball milling is 9 hours; and finally, performing high-energy nanocrystallization, wherein the pressure of the high-energy nanocrystallization is 50MPa, and the time of the high-energy nanocrystallization is 4 hours. The solid is uniformly dispersed in the solvent to obtain a uniform and stable first slurry.
(4) And (2) putting the Carbon Fibers (CF) into another part of the dispersion liquid in the step (1) to obtain slurry of the carbon fibers with the solid content of 5%.
(5) Carrying out low-energy ball milling on the carbon fiber slurry obtained in the step (4), wherein equipment adopted by the low-energy ball milling is an upright ball mill, grinding balls are zirconium balls, ceramic balls and the like with the sizes of 8-15 mm, the rotating speed of the low-energy ball milling is 50Hz, and the low-energy ball milling time is 12 h; then shearing and dispersing at the shearing speed of 2000rpm for 0.5 h; then high-energy ball milling is carried out, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.7-0.9 mm, the rotating speed of the high-energy ball milling is 1250rpm, and the time of the high-energy ball milling is 7 hours; and finally, performing high-energy nanocrystallization, wherein the pressure of the high-energy nanocrystallization is 45MPa, and the time of the high-energy nanocrystallization is 3 h. The solid is uniformly dispersed in the solvent to obtain a uniform and stable second slurry.
(6) And mixing the first slurry and the second slurry for 3h, wherein the mass ratio of the carbon nanotubes in the first slurry to the carbon fibers in the second slurry is 3:97 during mixing, so that uniform and stable slurry of the one-dimensional carbon fiber/carbon nanotube composite material is obtained.
And (3) testing results: the rate capability of the lithium battery prepared by adopting the one-dimensional carbon fiber/carbon nanotube composite material is greatly improved, and the 30C capacity reaches 78.5 percent of the 1C capacity.
Example 3
(1) The organic high molecular polymer PE was added to the solvent NMP to obtain a dispersion having a solid content of 0.1%.
(2) Mixing Carbon Nano Tube (CNT) and Carbon Fiber (CF) powder according to a mass ratio of 1:99, uniformly dispersing the Carbon Nano Tube (CNT) and the Carbon Fiber (CF) powder to obtain mixed powder, and mixing the mixed powder with the dispersion liquid obtained in the step (1) to obtain the conductive paste with the solid content of 16%.
(3) And (3) firstly, carrying out low-energy ball milling on the conductive slurry obtained in the step (2), wherein the low-energy ball milling adopts an apparatus of an upright ball mill, the grinding balls are zirconium balls, ceramic balls and the like with the sizes of 8-10 mm, the rotating speed of the low-energy ball milling is 45Hz, and the low-energy ball milling time is 12.5 h.
(4) Then, the mixture is subjected to shear dispersion, wherein the shear speed is 1300rpm, and the shear dispersion time is 1.5 h.
(5) And then performing high-energy ball milling, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.4-0.6 mm, the rotating speed of the high-energy ball milling is 1300rpm, and the time of the high-energy ball milling is 6 hours.
(6) And finally, performing high-energy nanocrystallization, wherein the pressure of the high-energy nanocrystallization is 30MPa, and the time of the high-energy nanocrystallization is 3 h. The solid is uniformly dispersed in the solvent, and uniform and stable slurry of the one-dimensional carbon fiber/carbon nanotube composite material is obtained.
And (3) testing results: the lithium battery prepared by the one-dimensional carbon fiber/carbon nanotube composite material has greatly improved rate capability, and the 30C capacity reaches 81.2 percent of 1C capacity.
Example 4
(1) Adding the mixture of organic high molecular polymer PVC and PP into solvent H2In O, a dispersion having a solid content of 2.5% was obtained.
(2) Mixing Carbon Nano Tube (CNT) and Carbon Fiber (CF) powder according to a mass ratio of 5:95, uniformly dispersing the Carbon Nano Tube (CNT) and the Carbon Fiber (CF) powder to obtain mixed powder, and mixing the mixed powder with the dispersion liquid obtained in the step (1) to obtain the conductive paste with the solid content of 8%.
(3) And (3) firstly, carrying out low-energy ball milling on the conductive slurry obtained in the step (2), wherein the low-energy ball milling adopts an apparatus of an upright ball mill, the grinding balls are zirconium balls, ceramic balls and the like with the sizes of 16-20 mm, the rotating speed of the low-energy ball milling is 60Hz, and the low-energy ball milling time is 5 h.
(4) Then, the mixture is subjected to shear dispersion, wherein the shear speed is 3000rpm, and the shear dispersion time is 1 h.
(5) And then performing high-energy ball milling, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.7-0.8 mm, the rotating speed of the high-energy ball milling is 1400rpm, and the time of the high-energy ball milling is 8 hours.
(6) Finally, the high-energy nanocrystallization is carried out, the pressure of the high-energy nanocrystallization is 35MPa, and the time of the high-energy nanocrystallization is 2 hours. The solid is uniformly dispersed in the solvent, and uniform and stable slurry of the one-dimensional carbon fiber/carbon nanotube composite material is obtained.
And (3) testing results: the rate capability of the lithium battery prepared by adopting the one-dimensional carbon fiber/carbon nanotube composite material is greatly improved, and the 30C capacity reaches 76.4 percent of the 1C capacity.
Example 5
(1) An organic high molecular polymer PS was added to a solvent NMP to obtain a dispersion having a solid content of 4%.
(2) And (2) putting Carbon Nanotubes (CNTs) into a part of the dispersion liquid in the step (1) to obtain a slurry of the carbon nanotubes with a solid content of 12.5%.
(3) Firstly, performing low-energy ball milling on the slurry of the carbon nano tube in the step (2), wherein the low-energy ball milling adopts an upright ball mill as equipment, grinding balls are zirconium balls, ceramic balls and the like with the size of 8-10 mm, the rotating speed of the low-energy ball milling is 40Hz, and the low-energy ball milling time is 10 h; then shearing and dispersing at the shearing speed of 2800rpm for 0.5 h; then high-energy ball milling is carried out, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.4-0.6 mm, the rotating speed of the high-energy ball milling is 1100rpm, and the time of the high-energy ball milling is 5 hours; and finally, performing high-energy nanocrystallization, wherein the pressure of the high-energy nanocrystallization is 40MPa, and the time of the high-energy nanocrystallization is 2 hours. The solid is uniformly dispersed in the solvent to obtain a uniform and stable first slurry.
(4) And (2) putting the Carbon Fibers (CF) into another part of the dispersion liquid in the step (1) to obtain slurry of the carbon fibers with the solid content of 12.5%.
(5) Carrying out low-energy ball milling on the carbon fiber slurry obtained in the step (4), wherein equipment adopted by the low-energy ball milling is an upright ball mill, grinding balls are zirconium balls, ceramic balls and the like with the sizes of 10-15 mm, the rotating speed of the low-energy ball milling is 35Hz, and the low-energy ball milling time is 15 h; then shearing and dispersing for 0.5h at the shearing speed of 2500 rpm; then high-energy ball milling is carried out, wherein the high-energy ball milling adopts a horizontal fine mill as equipment, the grinding balls are zirconium balls, ceramic balls and the like with the size of 0.8-0.9 mm, the rotating speed of the high-energy ball milling is 1500rpm, and the time of the high-energy ball milling is 6 hours; finally, high-energy nanocrystallization is carried out, the pressure of the high-energy nanocrystallization is 35MPa, and the time of the high-energy nanocrystallization is 2 hours. The solid is uniformly dispersed in the solvent to obtain a uniform and stable second slurry.
(6) And mixing the first slurry and the second slurry for 5 hours, wherein the mass ratio of the carbon nanotubes in the first slurry to the carbon fibers in the second slurry is 5.5:94.5, and uniform and stable slurry of the one-dimensional carbon fiber/carbon nanotube composite material is obtained.
And (3) testing results: the rate capability of the lithium battery prepared by adopting the one-dimensional carbon fiber/carbon nanotube composite material is greatly improved, and the 30C capacity reaches 78.3 percent of the 1C capacity.
The applicant states that the present invention is illustrated in detail by the above examples, but the present invention is not limited to the above detailed methods, i.e. it is not meant that the present invention must rely on the above detailed methods for its implementation. It should be understood by those skilled in the art that any modification of the present invention, equivalent substitutions of the raw materials of the product of the present invention, addition of auxiliary components, selection of specific modes, etc., are within the scope and disclosure of the present invention.
Claims (21)
1. The preparation method of the one-dimensional carbon fiber/carbon nanotube composite material is characterized by comprising the steps of carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on conductive slurry in sequence;
the conductive slurry is a mixed slurry of carbon fibers and carbon nanotubes, and the mass ratio of the carbon nanotubes to the carbon fibers in the mixed slurry is 0.1:99.9-10: 90;
the low-energy ball milling comprises the following steps: performing ball milling at the rotation speed of 10Hz-70Hz, wherein the size of the grinding balls used in the low-energy ball milling process is 5mm-10 mm;
the shear dispersion is as follows: shearing at the rotation speed of 1000-4000 rpm;
the high-energy ball milling comprises the following steps: performing ball milling at the rotation speed of 700rpm-1500rpm, wherein the size of grinding balls used in the high-energy ball milling process is 0.3mm-1 mm;
homogenizing by a high-energy nanocrystallization machine, wherein the pressure in the high-energy nanocrystallization process is 10-50 MPa;
the equipment adopted by the low-energy ball mill is an upright ball mill, and the equipment adopted by the shearing dispersion is a high-shear dispersion machine.
2. The method according to claim 1, wherein the solid content of the electroconductive paste is 1% to 20%.
3. The method of claim 1, wherein the low energy ball milling is performed for a time of 0.5h to 20 h.
4. The preparation method according to claim 1, wherein the grinding balls used in the low-energy ball milling process are zirconium balls and/or ceramic balls.
5. The method of claim 1, wherein the shear dispersion time is 0.1h to 2 h.
6. The preparation method of claim 1, wherein the high energy ball milling time is 1h to 10 h.
7. The preparation method according to claim 1, wherein the grinding balls used in the high-energy ball milling process are zirconium balls and/or ceramic balls.
8. The method according to claim 1, wherein the time for the high-energy nanocrystallization is 1 to 5 hours.
9. The production method according to claim 1, wherein the carbon fiber has a diameter of 1 μm to 100 μm.
10. The production method according to claim 1, wherein the carbon fiber has a specific surface area of 1m2/g-100m2/g。
11. The method according to claim 1, wherein the carbon nanotubes have a diameter of 10nm to 100 nm.
12. The production method according to claim 1, wherein the carbon nanotube has a specific surface area of 50m2/g-300m2/g。
13. The method of claim 1, wherein the mixed slurry of carbon fibers and carbon nanotubes is prepared by: dispersing carbon fibers and carbon nanotubes into a dispersion liquid composed of an organic high molecular polymer and a solvent to obtain a mixed slurry of the carbon fibers and the carbon nanotubes.
14. The method of claim 13, wherein the carbon fibers and the carbon nanotubes are dispersed in the dispersion in a manner of: respectively dispersing carbon fibers and carbon nanotubes into the dispersion liquid; or mixing the carbon fiber and the carbon nano tube uniformly to obtain mixed powder, and dispersing the mixed powder into the dispersion liquid.
15. The method according to claim 13, wherein the organic high molecular polymer in the dispersion comprises any one or a mixture of at least two of polyvinylpyrrolidone PVP, polyvinylidene fluoride PVDF, polytetrafluoroethylene PTFE, polyvinyl chloride PVC, acrylonitrile-styrene-butadiene copolymer ABS, polyethylene PE, polypropylene PP, or polystyrene PS.
16. The method of claim 13, wherein the solvent in the dispersion comprises N-methylpyrrolidone (NMP), H2Any one or a mixture of at least two of O, methanol or ethanol.
17. The method for preparing according to claim 1, characterized in that it comprises the following steps:
(1) adding an organic high molecular polymer into a solvent to ensure that the solid content is 0.1-5% to obtain a dispersion liquid;
(2) uniformly mixing the carbon nano tube and the carbon fiber according to the mass ratio of 0.1:99.9-10:90 to obtain mixed powder, and then dispersing the mixed powder into the dispersion liquid obtained in the step (1) to obtain conductive slurry, wherein the solid content of the conductive slurry is 1-20%;
(3) and (3) sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on the conductive slurry obtained in the step (2) to obtain the carbon fiber/carbon nanotube composite material.
18. The method for preparing according to claim 1, characterized in that it comprises the following steps:
(A) adding an organic high molecular polymer into a solvent to ensure that the solid content is 0.1-5% to obtain a dispersion liquid;
(B) respectively putting carbon nano tubes and carbon fibers into the dispersion liquid obtained in the step (A) to obtain conductive slurry, wherein the mass ratio of the carbon nano tubes to the carbon fibers in the conductive slurry is 0.1:99.9-10:90, and the solid content of the conductive slurry is 1% -20%;
(C) and (C) sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization on the conductive slurry obtained in the step (B) to obtain the carbon fiber/carbon nanotube composite material.
19. The method for preparing according to claim 1, characterized in that it comprises the following steps:
(a) adding an organic high molecular polymer into a solvent to ensure that the solid content is 0.1-5% to obtain a dispersion liquid;
(b) dispersing carbon nanotubes into a part of the dispersion liquid obtained in the step (a) to obtain slurry of the carbon nanotubes, and sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization to obtain first slurry;
(c) dispersing carbon fibers into the other part of the dispersion liquid obtained in the step (a) to obtain slurry of the carbon fibers, and sequentially carrying out low-energy ball milling, shearing dispersion, high-energy ball milling and high-energy nanocrystallization to obtain second slurry;
(d) and mixing the first slurry and the second slurry for 0.1-5 h to obtain the carbon fiber/carbon nanotube composite material.
20. A one-dimensional carbon fiber/carbon nanotube composite material prepared by the method of any one of claims 1-19.
21. Use of the one-dimensional carbon fiber/carbon nanotube composite of claim 20 in a lithium ion battery.
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