CN109671952B - Microcrystalline graphene-based composite conductive slurry for lithium battery and preparation method thereof - Google Patents
Microcrystalline graphene-based composite conductive slurry for lithium battery and preparation method thereof Download PDFInfo
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- H01B1/00—Conductors or conductive bodies characterised by the conductive materials; Selection of materials as conductors
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- H—ELECTRICITY
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Abstract
The invention discloses microcrystalline graphene-based composite conductive slurry for a lithium battery and a preparation method thereof. The microcrystalline graphene-based composite conductive slurry can remarkably reduce the internal resistance of a lithium battery with a small addition amount, and improve the energy density and the rate discharge performance of the battery. The microcrystalline graphene-based composite conductive slurry prepared by the method is uniform, stable and not easy to delaminate, the process flow is simple, the preparation cost is low, and the industrial continuous production is easy to realize.
Description
Technical Field
The invention relates to the technical field of negative electrode materials, in particular to microcrystalline graphene-based composite conductive slurry for a lithium battery and a preparation method thereof.
Background
In the charge-discharge cycle of the lithium battery, the positive pole piece and the negative pole piece can generate polarization phenomena and polarization voltage, the long-term polarization voltage can accelerate the precipitation of negative pole metal lithium, and the precipitation of lithium can even pierce a battery diaphragm to cause short circuit. In order to accelerate the rapid homing of electrons, weaken polarization and ensure that the electrode has good charge and discharge performance, a certain amount of conductive agent is usually added during the manufacture of the pole piece, so that the pole piece and a current collector play a role in collecting micro-current between active substances, the contact resistance of the electrode is reduced, and the charge and discharge performance of the lithium battery is improved.
With the development of electric automobiles, the requirements of lithium ion power batteries on high multiplying power and high energy density are increased, the current and power for charging and discharging lithium batteries are greatly increased, and a conductive agent with less additive amount and more excellent comprehensive performance is required to be used for increasing the transfer speed of electrons in the electrodes, reducing the polarization of the electrodes, reducing the internal resistance and improving the performance of the batteries.
The graphene has a unique two-dimensional sheet structure and super-strong conductivity, can be in point-surface contact with electrode active substances as a novel conductive agent, can exert the maximum conductive effect with less usage, saves space, uses more active substances, and improves the capacity and rate capability of the lithium battery. The crystalline flake graphite has good orientation consistency, but a material with poor orientation and good homogeneity is required in the lithium battery electrode material, the microcrystalline graphite has tiny crystal grains, poor orientation and good homogeneity, and the prepared microcrystalline graphene has more folds and smaller laminas than the graphene prepared by large flake graphite, and can be attached to the electrode material and weaken the obstruction to ion transmission.
The graphene conductive paste is a novel efficient conductive agent, but the graphene is high in preparation cost and difficult to disperse, and has the defects of blocking ion transmission and the like. At present, graphene conductive slurry is prepared by dispersing graphene in a solvent to form a dispersion liquid, and the graphene conductive slurry has the disadvantages of complex process, high preparation cost and poor dispersion performance.
The graphene prepared by the liquid phase stripping method has few defects and few layers, is suitable for large-scale production, and is one of the hot spots of the current research in the field of large-scale graphene preparation. Chinese patent application publication No. CN 104843679A discloses a method for preparing microcrystalline graphene by solvent thermal exfoliation of microcrystalline graphite, which comprises the steps of adding microcrystalline graphite into a mixed solvent, heating the solvent, ultrasonically exfoliating, and centrifugally separating to obtain the microcrystalline graphene. The graphene prepared by the method has small concentration and low yield.
Disclosure of Invention
In view of the above, the present invention provides a microcrystalline graphene-based composite conductive paste for a lithium battery and a preparation method thereof, which can effectively solve the problems of complicated process, high preparation cost and poor dispersion performance of the existing preparation method of graphene conductive paste.
In order to achieve the purpose, the invention adopts the following technical scheme:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP into an NMP solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.1-0.5%; adding microcrystalline graphite with the particle size of 800-1000 meshes and the fixed carbon content of 99.0-99.9% into an NMP solution, wherein the concentration of the microcrystalline graphite is 10-20mg/mL, and uniformly stirring to obtain a suspension 1;
(2) heating the suspension 1 to 150-;
(3) standing the suspension 2 for 5-7 days, naturally settling the un-peeled graphite, and separating the upper suspension to obtain an NMP dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 3-5, the yield of the graphene is 5-10%, and the concentration is 0.5-1.0 mg/mL;
(4) removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to a required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 5-20 parts of microcrystalline graphene, 1-10 parts of carbon nano tubes, 5-20 parts of conductive carbon black, 1-5 parts of binder, 5-20 parts of dispersant, 0.5-1 part of activator, 20-60 parts of solvent and 3-15 parts of binder; and uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 2kW-5kW, and carrying out ultrasonic-assisted grinding for 1-5h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry.
As a preferred scheme, the carbon nanotube has a tube diameter of 5-25nm, a length of 1-5 μm, a wall thickness of 5-10 nm, and a purity: is more than 99.8 percent.
Preferably, the conductive carbon black D50=5-20nm, has a specific resistance value of 0.10-0.52 omega cm, and is prepared by modifying a silane coupling agent KH550 with a mass fraction of 2.5%.
Preferably, the activating agent in step (5) is a lithium salt of carboxylic acid.
As a preferred scheme, the binder is one or more of sodium carboxymethylcellulose, carboxyethyl cellulose and hydroxypropyl cellulose.
The microcrystalline graphene-based composite conductive slurry for the lithium battery is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 1000-3000 mPa.s.
Compared with the prior art, the invention has obvious advantages and beneficial effects, and specifically, the technical scheme includes that:
the preparation method can obtain high-purity few-layer graphene with high yield, realizes good dispersibility of the graphene and good cohesiveness of the conductive slurry, and the prepared composite conductive slurry can remarkably reduce the internal resistance of the lithium battery with less consumption, and improves the energy density and the rate discharge performance of the battery. The method has the advantages of simple process flow, low preparation cost, uniformity, stability, difficulty in layering and easiness in realizing industrial continuous production.
Drawings
FIG. 1 is a schematic diagram of a production scheme of the present invention;
FIG. 2 is a Raman spectrum of example 1 of the present invention;
FIG. 3 is an XRD pattern for example 1 of the present invention;
FIG. 4 is an SEM photograph of example 1 of the present invention.
Detailed Description
The invention discloses a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery, which comprises the following steps of:
(1) adding a surface active agent PVP (polyvinylpyrrolidone) into an NMP (N-methyl pyrrolidone) solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.1-0.5%; then microcrystalline graphite with the particle size of 800-1000 meshes and the fixed carbon content of 99.0-99.9 percent is added into the NMP solution, the concentration of the microcrystalline graphite is 10-20mg/mL, and the suspension 1 is obtained after uniform stirring.
(2) Heating the suspension 1 to 150-.
(3) Standing the turbid liquid 2 for 5-7 days, naturally settling the un-peeled graphite, and separating the upper layer suspension to obtain an NMP (N-methyl pyrrolidone) dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of the microcrystalline graphene layers is 3-5, the graphene yield is 5-10%, and the concentration is 0.5-1.0 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to a required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 5-20 parts of microcrystalline graphene, 1-10 parts of carbon nano tubes, 5-20 parts of conductive carbon black, 1-5 parts of binder, 5-20 parts of dispersant, 0.5-1 part of activator, 20-60 parts of solvent and 3-15 parts of binder; and uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 2kW-5kW, and carrying out ultrasonic-assisted grinding for 1-5h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 5-25nm, the length of 1-5 mu m, the wall thickness of 5-10 nm and the purity: 99.8 percent, the conductive carbon black D50=5-20nm, the specific resistance value is 0.10-0.52 omega cm, the conductive carbon black is prepared by modifying 2.5 percent by mass of silane coupling agent KH550, the activating agent is lithium carboxylate, and the binder is one or more of sodium carboxymethyl cellulose, carboxyethyl cellulose and hydroxypropyl cellulose.
The invention also discloses the microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by adopting the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 1000-3000 mPa.s.
The invention is illustrated in more detail below in the following examples:
example 1:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP (polyvinylpyrrolidone) into an NMP (N-methyl pyrrolidone) solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.1%; and adding microcrystalline graphite with the particle size of 800 meshes and the fixed carbon content of 99.0% into an NMP solution, wherein the concentration of the microcrystalline graphite is 10mg/mL, and uniformly stirring to obtain a suspension 1.
(2) Heating the suspension 1 to 150 ℃, stirring and refluxing for 48h at the stirring speed of 200rpm, and in the process, starting ultrasound with the ultrasound frequency of 20000Hz and the ultrasound power of 2kW, and performing ultrasound for 30min every 30min to obtain the suspension 2 with the mass fraction of 0.5 wt%.
(3) Standing the turbid liquid 2 for 5 days, naturally settling the un-peeled graphite, and separating the upper layer of suspension to obtain an NMP (N-methyl pyrrolidone) dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 3, the yield of the graphene is 10%, and the concentration is 0.5 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to be the required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 5 parts of microcrystalline graphene, 1 part of carbon nano tube, 5 parts of conductive carbon black, 1 part of binder, 5 parts of dispersant, 0.5 part of activator, 20 parts of solvent and 3 parts of binder; and (3) uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 4kW, and carrying out ultrasonic-assisted grinding for 5h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 5nm, the length of 1 mu m, the wall thickness of 5nm and the purity: the conductive carbon black is characterized by being more than 99.8 percent, the conductive carbon black D50=5nm, the specific resistance value is 0.10 omega-cm, the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5 percent, the activating agent is lithium carboxylate, and the binder is sodium carboxymethylcellulose.
The invention also discloses microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 3000 mPa.s.
Example 2:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP into an NMP solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.5%; and adding microcrystalline graphite with the particle size of 1000 meshes and the fixed carbon content of 99.9% into the NMP solution, wherein the concentration of the microcrystalline graphite is 20mg/mL, and uniformly stirring to obtain a suspension 1.
(2) Heating the suspension 1 to 200 ℃, stirring and refluxing for 72h at the stirring speed of 400rpm, starting ultrasound in the process, wherein the ultrasound frequency is 25000Hz, the ultrasound power is 3kW, and performing ultrasound for 30min every 30min to obtain a suspension 2 with the mass fraction of 1.5 wt%.
(3) Standing the suspension liquid 2 for 7 days, naturally settling the un-peeled graphite, and separating the upper suspension liquid to obtain an NMP dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 3, the yield of the graphene is 5%, and the concentration is 0.5 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to be the required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 20 parts of microcrystalline graphene, 10 parts of carbon nano tubes, 20 parts of conductive carbon black, 5 parts of a binder, 20 parts of a dispersing agent, 1 part of an activating agent, 60 parts of a solvent and 15 parts of a binder; and (3) uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 5kW, and carrying out ultrasonic-assisted grinding for 5h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 25nm, the length of 5 mu m, the wall thickness of 10nm and the purity: the conductive carbon black is characterized by being more than 99.8 percent, the conductive carbon black D50=20nm, the specific resistance value is 0.52 omega-cm, the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5 percent, the activating agent is lithium carboxylate, and the binder is carboxyethyl cellulose.
The invention also discloses microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 2000 mPa.s.
Example 3:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP into an NMP solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.2%; and adding microcrystalline graphite with the particle size of 900 meshes and the fixed carbon content of 99.2% into an NMP solution, wherein the concentration of the microcrystalline graphite is 15mg/mL, and uniformly stirring to obtain a suspension 1.
(2) Heating the suspension 1 to 160 ℃, stirring and refluxing for 50h at the stirring speed of 250rpm, starting ultrasound in the process, wherein the ultrasound frequency is 22000Hz, the ultrasound power is 2.2kW, and performing ultrasound for 30min every 30min to obtain the suspension 2 with the mass fraction of 0.8 wt%.
(3) Standing the suspension liquid 2 for 6 days, naturally settling the un-peeled graphite, and separating the upper suspension liquid to obtain an NMP dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 4, the yield of the graphene is 8%, and the concentration is 0.6 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to be the required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 10 parts of microcrystalline graphene, 5 parts of carbon nano tubes, 13 parts of conductive carbon black, 3 parts of a binder, 14 parts of a dispersing agent, 0.6 part of an activating agent, 30 parts of a solvent and 8 parts of a binder; and (3) uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 3kW, and carrying out ultrasonic-assisted grinding for 4h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 14nm, the length of 2 mu m, the wall thickness of 8nm and the purity: the conductive carbon black is characterized by being more than 99.8 percent, the conductive carbon black D50=10nm, the specific resistance value is 0.22 omega-cm, the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5 percent, the activating agent is lithium carboxylate, and the binder is hydroxypropyl cellulose.
The invention also discloses microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 1500 mPa.s.
Example 4:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP into an NMP solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.3%; and adding microcrystalline graphite with the particle size of 900 meshes and the fixed carbon content of 99.5% into an NMP solution, wherein the concentration of the microcrystalline graphite is 18mg/mL, and uniformly stirring to obtain a suspension 1.
(2) And heating the suspension 1 to 180 ℃, stirring and refluxing for 60h at the stirring speed of 300rpm, starting ultrasound in the process, wherein the ultrasound frequency is 24000Hz, the ultrasound power is 2.5kW, and performing ultrasound for 30min every 30min to obtain the suspension 2 with the mass fraction of 1.2 wt%.
(3) Standing the turbid liquid 2 for 5.5 days, naturally settling the un-peeled graphite, and separating the upper layer suspension to obtain an NMP (N-methyl pyrrolidone) dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 4, the yield of the graphene is 8%, and the concentration is 0.8 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to be the required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 16 parts of microcrystalline graphene, 7 parts of carbon nano tubes, 14 parts of conductive carbon black, 4 parts of a binder, 14 parts of a dispersing agent, 0.8 part of an activating agent, 40 parts of a solvent and 14 parts of a binder; and (3) uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 5kW, and carrying out ultrasonic-assisted grinding for 3h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 22nm, the length of 3 mu m, the wall thickness of 8nm and the purity: the conductive carbon black is characterized by being more than 99.8 percent, the conductive carbon black D50=14nm, the specific resistance value is 0.32 omega-cm, the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5 percent, the activating agent is lithium carboxylate, and the binder is a mixture of sodium carboxymethylcellulose and carboxyethyl cellulose.
The invention also discloses microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 1500 mPa.s.
Example 5:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP (polyvinylpyrrolidone) into an NMP (N-methyl pyrrolidone) solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.4%; and adding microcrystalline graphite with the particle size of 950 meshes and the fixed carbon content of 99.8% into an NMP solution, wherein the concentration of the microcrystalline graphite is 16mg/mL, and uniformly stirring to obtain a suspension 1.
(2) Heating the suspension 1 to 190 ℃, stirring and refluxing for 65h at the stirring speed of 320rpm, starting ultrasound in the process, wherein the ultrasound frequency is 2400 Hz, the ultrasound power is 2.6kW, and performing ultrasound for 30min every 30min to obtain the suspension 2 with the mass fraction of 1.4 wt%.
(3) Standing the suspension 2 for 6.5 days, naturally settling the un-peeled graphite, and separating the upper suspension to obtain an NMP dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 4, the yield of the graphene is 8%, and the concentration is 0.9 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to be the required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 14 parts of microcrystalline graphene, 4 parts of carbon nano tubes, 17 parts of conductive carbon black, 2 parts of a binder, 18 parts of a dispersing agent, 0.7 part of an activating agent, 40 parts of a solvent and 11 parts of a binder; and (3) uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 2kW, and carrying out ultrasonic-assisted grinding for 5h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 18nm, the length of 4 mu m, the wall thickness of 8nm and the purity: the conductive carbon black is characterized by being more than 99.8 percent, the conductive carbon black D50=12nm, the specific resistance value is 0.38 omega-cm, the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5 percent, the activating agent is lithium carboxylate, and the binder is sodium carboxymethylcellulose, carboxyethyl cellulose and hydroxypropyl cellulose.
The invention also discloses microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 2500 mPa.s.
Example 6:
a preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery comprises the following steps:
(1) adding a surface active agent PVP (polyvinylpyrrolidone) into an NMP (N-methyl pyrrolidone) solvent to form an NMP solution, wherein the mass concentration of the PVP is 0.35%; and adding microcrystalline graphite with the particle size of 880 meshes and the fixed carbon content of 99.4% into the NMP solution, wherein the concentration of the microcrystalline graphite is 15mg/mL, and uniformly stirring to obtain a suspension 1.
(2) Heating the suspension 1 to 190 ℃, stirring and refluxing for 70h at the stirring speed of 380rpm, starting ultrasound in the process, wherein the ultrasound frequency is 23000Hz, the ultrasound power is 2.4kW, and performing ultrasound for 30min every 30min to obtain the suspension 2 with the mass fraction of 1.3 wt%.
(3) Standing the suspension liquid 2 for 7 days, naturally settling the un-peeled graphite, and separating the upper suspension liquid to obtain an NMP dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 5, the yield of the graphene is 8%, and the concentration is 0.9 mg/mL.
(4) Removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to be the required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 18 parts of microcrystalline graphene, 3 parts of carbon nano tubes, 11 parts of conductive carbon black, 4 parts of a binder, 10 parts of a dispersing agent, 0.6 part of an activating agent, 50 parts of a solvent and 11 parts of a binder; and (3) uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine with the power of 4.5kW, starting ultrasonic waves, wherein the ultrasonic power is 4kW, and carrying out ultrasonic-assisted grinding for 5 hours to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry. The carbon nano tube has the tube diameter of 22nm, the length of 2 mu m, the wall thickness of 8nm and the purity: 99.8 percent, the conductive carbon black D50=15nm, the specific resistance value is 0.28 omega cm, the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5 percent, the activating agent is lithium carboxylate, and the binder is sodium carboxymethylcellulose.
The invention also discloses microcrystalline graphene-based composite conductive slurry for the lithium battery, which is prepared by the preparation method of the microcrystalline graphene-based composite conductive slurry for the lithium battery, and the viscosity of the microcrystalline graphene-based composite conductive slurry is 1800 mPa.s.
The design of the invention is characterized in that: the preparation method can obtain high-purity few-layer graphene with high yield, realizes good dispersibility of the graphene and good cohesiveness of the conductive slurry, and the prepared composite conductive slurry can remarkably reduce the internal resistance of the lithium battery with less consumption, and improves the energy density and the rate discharge performance of the battery. The microcrystalline graphene-based composite conductive slurry prepared by the method is uniform, stable and not easy to delaminate, the process flow is simple, the preparation cost is low, and the industrial continuous production is easy to realize.
The above description is only a preferred embodiment of the present invention, and is not intended to limit the technical scope of the present invention, so that any minor modifications, equivalent changes and modifications made to the above embodiment according to the technical spirit of the present invention are within the technical scope of the present invention.
Claims (6)
1. A preparation method of microcrystalline graphene-based composite conductive slurry for a lithium battery is characterized by comprising the following steps: the method comprises the following steps:
(1) adding a surface active agent PVP into an NMP solvent to form a mixed solution, wherein the mass concentration of the PVP is 0.1-0.5%; adding microcrystalline graphite with the particle size of 800-1000 meshes and the fixed carbon content of 99.0-99.9% into an NMP solution, wherein the concentration of the microcrystalline graphite is 10-20mg/mL, and uniformly stirring to obtain a suspension 1;
(2) heating the suspension 1 to 150-;
(3) standing the suspension 2 for 5-7 days, naturally settling the un-peeled graphite, and separating the upper suspension to obtain an NMP dispersion liquid of the microcrystalline graphene; the dispersing agent in the NMP dispersion liquid of the microcrystalline graphene is PVP, the solvent is NMP, the number of layers of the microcrystalline graphene is 3-5, the yield of the graphene is 5-10%, and the concentration is 0.5-1.0 mg/mL;
(4) removing part of NMP solvent from the microcrystalline graphene NMP dispersion liquid prepared in the step (3) through a vacuum distiller, and adjusting the mass fraction of graphene to a required concentration;
(5) adding an activating agent, a carbon nano tube, a binder and conductive carbon black into the NMP dispersion liquid of the microcrystalline graphene with the adjusted concentration under stirring, and supplementing a dispersing agent to ensure that the graphene conductive slurry comprises the following components in percentage by mass: 5-20 parts of microcrystalline graphene, 1-10 parts of carbon nano tubes, 5-20 parts of conductive carbon black, 1-5 parts of binder, 5-20 parts of dispersant, 0.5-1 part of activator, 20-60 parts of solvent and 3-15 parts of binder; and uniformly stirring to obtain mixed slurry, feeding the mixed slurry into an ultrasonic grinding machine, starting ultrasonic waves, wherein the ultrasonic power is 2kW-5kW, and carrying out ultrasonic-assisted grinding for 1-5h to obtain the stably-dispersed microcrystalline graphene-based composite conductive slurry.
2. The preparation method of the microcrystalline graphene-based composite conductive paste for the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the carbon nano tube has the tube diameter of 5-25nm, the length of 1-5 mu m, the wall thickness of 5-10 nm and the purity of more than 99.8 percent.
3. The preparation method of the microcrystalline graphene-based composite conductive paste for the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the conductive carbon black D50=5-20nm, the specific resistance value is 0.10-0.52 omega cm, and the conductive carbon black is prepared by modifying a silane coupling agent KH550 with the mass fraction of 2.5%.
4. The preparation method of the microcrystalline graphene-based composite conductive paste for the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the activating agent in the step (5) is lithium carboxylate.
5. The preparation method of the microcrystalline graphene-based composite conductive paste for the lithium battery as claimed in claim 1, wherein the preparation method comprises the following steps: the binder is one or more of sodium carboxymethylcellulose, carboxyethyl cellulose and hydroxypropyl cellulose.
6. The utility model provides a compound electrically conductive thick liquids of micrite graphite alkene base for lithium cell which characterized in that: the microcrystalline graphene-based composite conductive paste for the lithium battery is prepared by the preparation method of the microcrystalline graphene-based composite conductive paste as claimed in any one of claims 1 to 5, and the viscosity of the microcrystalline graphene-based composite conductive paste is 1000-3000mPa.
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