CN110600742A - Preparation method and application of graphene conductive slurry - Google Patents
Preparation method and application of graphene conductive slurry Download PDFInfo
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- CN110600742A CN110600742A CN201910869827.9A CN201910869827A CN110600742A CN 110600742 A CN110600742 A CN 110600742A CN 201910869827 A CN201910869827 A CN 201910869827A CN 110600742 A CN110600742 A CN 110600742A
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- 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
- H01B1/20—Conductive material dispersed in non-conductive organic material
- H01B1/24—Conductive material dispersed in non-conductive organic material the conductive material comprising 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
- 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
- H01M4/625—Carbon or graphite
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention relates to a preparation method and application of graphene conductive slurry, wherein the graphene conductive slurry is a compound of graphene and N-methylpyrrolidone (NMP). Firstly, crushing and screening the raw material flake graphite by using a jet mill; adding an oxidant and an intercalating agent into the crushed raw materials according to a certain proportion, uniformly mixing, and fully reacting in a water bath; repeatedly washing the reaction solution with deionized water, centrifuging, and drying; carrying out high-temperature puffing treatment on the dried powder to obtain a precursor; and finally, adding NMP into the precursor, and carrying out ultrasonic treatment for a certain time to obtain the graphene conductive slurry. The graphene in the slurry has the characteristics of small sheet diameter (less than or equal to 20 mu m, controllable sheet diameter), low defect and porosity. The key technical problem that graphene is used as a lithium battery positive electrode conductive agent in engineering application at present is solved. The preparation method is simple, low in cost and suitable for engineering production. The prepared graphene slurry is compounded with the carbon nanotube slurry to be used as a conductive additive to be applied to the positive electrode of the lithium battery, and the energy density and the rate capability of the lithium battery can be remarkably improved.
Description
Technical Field
The invention discloses a preparation method and application of graphene conductive slurry, and belongs to the technical field of battery manufacturing.
Background
Graphene is a novel two-dimensional nano material, has super-strong conductivity, and is the best material for the current conductivity. With simultaneous ultrahigh electronsMobility (200000 cm)2V.S) as conductive additive, the conductive additive can greatly improve the conductivity of the positive electrode material, effectively shorten the electron transmission path during the charge and discharge of the battery, and accelerate the transmission speed of the positive electrode material and the battery. The method has important significance for improving the energy density, rate capability, cycle life and the like of the lithium battery. However, the current graphene used as a conductive additive for the positive electrode of the lithium battery has the following engineering technical problems:
firstly, the graphene obtained by the existing batch preparation method has high defect and poor conductivity, is used for a battery, and has no obvious performance improvement or even worsens the performance of the battery;
secondly, due to the steric effect of ions, lithium ions are difficult to penetrate through a six-membered ring of the graphene, and when the battery works, the graphene brings certain negative effects on the transmission of the lithium ions in the electrolyte, so that the power performance of the lithium ion battery is influenced. The larger the sheet diameter, the more significant the effect of graphene on lithium ion inhibition, and the poorer the rate capability exhibited. The method can be solved by graphene banding, porosification or reducing the size and the like.
Thirdly, the graphene prepared in batch at present has a wide distribution range of the sheet diameter, and shows poor consistency of battery performance when being applied to a lithium battery as a conductive agent.
In addition, the graphene/carbon nano tube is a mainstream composite conductive agent at present, and when the graphene/carbon nano tube is applied to a battery, the addition proportion of the conductive agent can be greatly reduced, and the energy density of the battery is improved. However, graphene is compounded with carbon tubes, so that stacking and curling of graphene are more likely to occur, and performance of graphene is limited. By reducing the graphene sheet diameter, the occurrence of this phenomenon can be effectively suppressed.
Therefore, in order to exert the electrochemical performance of graphene serving as a conductive agent in the positive electrode to the maximum extent so as to prepare a high-performance battery device product, the development of the graphene conductive slurry applicable to the field of energy storage batteries is of great significance.
Disclosure of Invention
The invention aims to provide a preparation method and application of graphene conductive slurry aiming at the defects existing in the lithium battery applying graphene as a conductive additive at present, and the technical scheme ensures good dispersion of graphene in an electrode and realizes rapid transmission and diffusion of electrons and ions by preparing a small-diameter (less than or equal to 20 mu m, controllable-diameter sheet), low-defect and porous graphene nanosheet. The graphene conductive paste provided by the invention is used as a conductive additive to be applied to a lithium battery anode, so that the polarization of the battery can be greatly reduced, and the rate capability and the energy density of the battery can be remarkably improved.
In order to achieve the above object, the present invention provides a method for preparing graphene conductive paste, which comprises the following steps:
firstly, crushing a flake graphite raw material to a flake diameter of less than or equal to 20 microns, and screening to obtain small-flake graphite with uniform flake diameter;
step two, uniformly mixing the crushed crystalline flake graphite with an intercalation agent and an oxidant, and fully reacting in a water bath at the temperature of 20-100 ℃, wherein the mass ratio of the crystalline flake graphite to the intercalation agent to the oxidant is 1: 1-10: 0.1-5;
step three, adding deionized water into the reaction liquid obtained in the step two, washing, filtering and drying into powder;
placing the dried powder in a muffle furnace, and heating for 10-60 s at 800-1000 ℃ to obtain a graphene precursor;
and step five, mixing the graphene precursor with N-methyl pyrrolidone, and performing ultrasonic oscillation for more than 30min to prepare the graphene conductive slurry with the solid content of 0.1-3%.
In one implementation, a jet mill is used to crush the flake graphite.
In one implementation, the purity of the flake graphite material is greater than or equal to 98%.
In one implementation, the intercalation agent is one or a mixture of concentrated sulfuric acid, concentrated nitric acid, perchloric acid, acetic acid and phosphoric acid.
In one implementation, the oxidant is one or a mixture of more of potassium permanganate, hydrogen peroxide, potassium dichromate and chromium trioxide.
The technical scheme of the invention also provides an application of the graphene conductive paste prepared by the method, which is characterized in that: the graphene conductive slurry and the carbon nano tube conductive slurry are mixed and dispersed through a planetary mixer to obtain composite conductive slurry, and the composite conductive slurry is used as a lithium battery conductive additive and added in the anode homogenizing process.
In one implementation, the mass ratio of graphene to carbon nanotubes in the graphene conductive paste and the carbon nanotube conductive paste is 1: 0.3-3.
In one implementation, the positive active material is one or a mixture of more of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickel cobalt manganate and lithium nickel cobalt aluminate, and the median particle size value is equivalent to the graphene sheet size value.
Compared with the prior art, the technical scheme of the invention has the following beneficial effects:
firstly, compared with several typical preparation methods (such as an oxidation-reduction method, a CVD method and the like), the graphene nanosheet prepared by the method has the advantages of few defects, high conductivity, low cost and the like, and can realize batch production.
And secondly, the preparation of small-particle-diameter (less than or equal to 20 mu m and controllable-particle-diameter) porous graphene nanosheets is realized, and the graphene nanosheets are used as positive electrode materials matched with particle diameters, can improve the conductivity, ensure the diffusion rate of lithium ions and obviously improve the relevant electrochemical performance of the battery. Meanwhile, the distribution range of the diameters of the graphene nanosheets is narrow, and the consistency of the battery is ensured.
Thirdly, graphene/carbon nanotubes are the mainstream composite conductive agent at present, but the problem that graphene generated during the compounding of the graphene and the carbon nanotubes is easy to agglomerate is not effectively solved in the industry. The graphene prepared by the method has the characteristics of small sheet diameter and difficult curling on the premise of ensuring the number of thin layers, and can be well compounded with the carbon nano tube by adopting conventional lithium battery slurry mixing equipment. The method is applied to the pole pieces, and can cooperatively construct a high-efficiency conductive network.
Detailed Description
The technical solution of the present invention will be further described with reference to the following examples.
Example 1
The preparation method of the graphene slurry with the sheet diameter of 5um comprises the following steps:
crushing raw material crystalline flake graphite with purity of more than or equal to 98% to 5um in flake diameter by using an airflow crusher, and screening to obtain small-size crystalline flake graphite with uniform flake diameter;
step two, uniformly mixing the crushed crystalline flake graphite with nitric acid, perchloric acid, acetic acid and potassium permanganate, and fully reacting in a water bath at 100 ℃, wherein the mass ratio of the crystalline flake graphite to the nitric acid to the perchloric acid to the acetic acid to the potassium permanganate is 1: 0.5: 1.6: 0.6: 0.4;
step three, adding deionized water into the reaction liquid in the step two, diluting, washing, filtering and drying for 3 hours at 50 ℃;
step four, placing the dried powder in a muffle furnace, and heating for 10s at 900 ℃ to obtain a graphene precursor;
and step five, adding a proper amount of N-methyl pyrrolidone into the prepared precursor to enable the solid content to be 3%, and ultrasonically oscillating for 30min to prepare the graphene conductive slurry with the solid content of 3%.
And step six, mixing the prepared graphene conductive slurry with a certain amount of carbon nano tube slurry, ensuring that the mass ratio of graphene to carbon nano tubes is 1:1, stirring and dispersing for 30min by using a planetary stirrer, and preparing the composite conductive slurry.
And seventhly, selecting a lithium iron phosphate material with D50 being 5um, adding the composite conductive slurry serving as a conductive additive in a lithium iron phosphate positive electrode homogenizing process according to the mass ratio of 1% (based on the mass ratio of the lithium iron phosphate material), and preparing the lithium iron phosphate battery according to the lithium ion battery process.
Example 2
The preparation method of the graphene slurry with the sheet diameter of 10um comprises the following steps:
step one, crushing the raw material crystalline flake graphite with the purity of more than or equal to 98% by using an airflow crusher until the flake graphite has the diameter of 10 microns, and screening to obtain small-diameter crystalline flake graphite with uniform flake diameter.
Step two, uniformly mixing the crushed crystalline flake graphite with nitric acid and potassium permanganate, and fully reacting in a water bath at 100 ℃, wherein the mass ratio of the crystalline flake graphite to the nitric acid to the potassium permanganate is 1: 2: 0.15;
step three, adding deionized water into the reaction liquid obtained in the step 2 for dilution, washing, filtering and drying at 50 ℃ for 3 hours;
step four, placing the dried powder in a muffle furnace, and heating for 10s at 900 ℃ to obtain a graphene precursor;
and step five, adding a proper amount of N-methyl pyrrolidone into the prepared precursor to enable the solid content to be 3%, and ultrasonically oscillating for 30min to prepare the graphene conductive slurry with the solid content of 3%.
And step six, mixing the prepared graphene conductive slurry with a certain amount of carbon nano tube slurry, ensuring that the mass ratio of graphene to carbon nano tubes is 1:1, stirring and dispersing for 30min by using a planetary stirrer, and preparing the composite conductive slurry.
And seventhly, selecting a lithium cobaltate material with D50 being 10 microns, adding the composite conductive slurry serving as a conductive additive in a lithium cobaltate positive electrode homogenizing process according to 1% (mass ratio of the lithium cobaltate material), and preparing the lithium cobaltate battery according to a lithium ion battery process.
Example 3
The preparation method of the graphene slurry with the sheet diameter of 15um comprises the following steps:
step one, crushing the raw material crystalline flake graphite with the purity of more than or equal to 98% by using an airflow crusher until the flake graphite has the diameter of 15 microns, and screening to obtain small-diameter crystalline flake graphite with uniform flake diameter.
Step two, uniformly mixing the crushed flake graphite with perchloric acid, phosphoric acid and chromium trioxide, and fully reacting in a water bath at 100 ℃, wherein the mass ratio of the flake graphite to the perchloric acid to the phosphoric acid to the chromium trioxide is 1: 3: 1.5: 0.8;
step three, adding deionized water into the reaction liquid obtained in the step 2 for dilution, washing, filtering and drying at 50 ℃ for 3 hours;
step four, placing the dried powder in a muffle furnace, and heating for 10s at 900 ℃ to obtain a graphene precursor;
and step five, adding the prepared precursor into N-methyl pyrrolidone to enable the solid content to be 3%, and performing ultrasonic oscillation for 30min to prepare the graphene conductive slurry with the solid content of 3%.
And step six, mixing the prepared graphene conductive slurry with a certain amount of carbon nano tube slurry, ensuring that the mass ratio of graphene to carbon nano tubes is 1:1, stirring and dispersing for 30min by using a planetary stirrer, and preparing the composite conductive slurry.
And seventhly, selecting a nickel cobalt lithium manganate material with D50 being 15um, adding the composite conductive slurry serving as a conductive additive in a mass ratio of 1% (based on the mass ratio of the nickel cobalt lithium manganate material) in the process of homogenizing the nickel cobalt lithium manganate positive electrode, and preparing the nickel cobalt lithium manganate battery according to a lithium ion battery process.
The graphene conductive slurry prepared by the process method has small graphene sheet diameter and high flatness, can be well compounded with the carbon nano tube, and is not easy to stack and curl. Meanwhile, due to the small sheet diameter and the porous characteristic of the graphene, unhindered lithium ion transmission is guaranteed. In addition, the distribution range of the graphene sheet diameter is narrow, and the consistency of the battery is ensured. The preparation method is simple, has low cost and can realize batch production. The prepared graphene has low defect, does not influence the current industrialization technology of battery manufacturing, and is beneficial to engineering application.
Claims (8)
1. A preparation method of graphene conductive paste is characterized by comprising the following steps: the method comprises the following steps:
firstly, crushing a flake graphite raw material to a flake diameter of less than or equal to 20 microns, and screening to obtain small-flake graphite with uniform flake diameter;
step two, uniformly mixing the crushed crystalline flake graphite with an intercalation agent and an oxidant, and fully reacting in a water bath at the temperature of 20-100 ℃, wherein the mass ratio of the crystalline flake graphite to the intercalation agent to the oxidant is 1: 1-10: 0.1-5;
step three, adding deionized water into the reaction liquid obtained in the step two, washing, filtering and drying into powder;
placing the dried powder in a muffle furnace, and heating for 10-60 s at 800-1000 ℃ to obtain a graphene precursor;
and step five, mixing the graphene precursor with N-methyl pyrrolidone, and performing ultrasonic oscillation for more than 30min to prepare the graphene conductive slurry with the solid content of 0.1-3%.
2. The method for preparing graphene conductive paste according to claim 1, wherein: and physically crushing and screening the crystalline flake graphite by using an airflow crusher.
3. The method for preparing graphene conductive paste according to claim 1, wherein: the purity of the flake graphite raw material is more than or equal to 98 percent.
4. The method for preparing graphene conductive paste according to claim 1, wherein: the intercalation agent is one or a mixture of more of concentrated sulfuric acid, concentrated nitric acid, perchloric acid, acetic acid and phosphoric acid.
5. The method for preparing graphene conductive paste according to claim 1, wherein: the oxidant is one or a mixture of more of potassium permanganate, hydrogen peroxide, potassium dichromate and chromium trioxide.
6. The application of the graphene conductive paste prepared by the method of claim 1 is characterized in that: the graphene conductive slurry and the carbon nano tube conductive slurry are mixed and dispersed through a planetary mixer to prepare composite conductive slurry which is used as a conductive additive to be added in the lithium battery anode homogenizing process.
7. The application of the graphene conductive paste according to claim 6, wherein: the mass ratio of graphene to carbon nanotubes in the graphene conductive slurry to the carbon nanotube conductive slurry is 1: 0.3-3.
8. The application of the graphene conductive paste according to claim 6, wherein: the positive active material is one or a mixture of more of lithium iron phosphate, lithium cobaltate, lithium manganate, lithium nickel cobalt manganese oxide and lithium nickel cobalt aluminate, and the median particle size value D50Comparable to the graphene sheet diameter value.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113614945A (en) * | 2020-10-19 | 2021-11-05 | 宁德新能源科技有限公司 | Positive electrode, and electrochemical device and electronic device comprising same |
| CN114792576A (en) * | 2022-06-22 | 2022-07-26 | 山东华冠智能卡有限公司 | Ultrahigh-frequency graphene conductive paste, preparation method, application and electronic tag |
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| CN106744833A (en) * | 2016-11-26 | 2017-05-31 | 耿亚琼 | A kind of method that segmentation prepares graphene oxide |
| CN107706422A (en) * | 2017-07-14 | 2018-02-16 | 常州第六元素材料科技股份有限公司 | Composite mortar of graphene and CNT and preparation method thereof, anode sizing agent and its method |
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Patent Citations (3)
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| CN105060283A (en) * | 2015-08-05 | 2015-11-18 | 深圳市三顺中科新材料有限公司 | Preparation method and application of graphene slurry |
| CN106744833A (en) * | 2016-11-26 | 2017-05-31 | 耿亚琼 | A kind of method that segmentation prepares graphene oxide |
| CN107706422A (en) * | 2017-07-14 | 2018-02-16 | 常州第六元素材料科技股份有限公司 | Composite mortar of graphene and CNT and preparation method thereof, anode sizing agent and its method |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN113614945A (en) * | 2020-10-19 | 2021-11-05 | 宁德新能源科技有限公司 | Positive electrode, and electrochemical device and electronic device comprising same |
| WO2022082365A1 (en) * | 2020-10-19 | 2022-04-28 | 宁德新能源科技有限公司 | Positive electrode, and electrochemical device and electronic device comprising same |
| CN113614945B (en) * | 2020-10-19 | 2022-09-09 | 宁德新能源科技有限公司 | Positive electrode, and electrochemical device and electronic device comprising same |
| CN114792576A (en) * | 2022-06-22 | 2022-07-26 | 山东华冠智能卡有限公司 | Ultrahigh-frequency graphene conductive paste, preparation method, application and electronic tag |
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Application publication date: 20191220 |