CN114188532B - Graphene anode material and preparation method and application thereof - Google Patents
Graphene anode material and preparation method and application thereof Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 202
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 164
- 239000010405 anode material Substances 0.000 title claims abstract description 83
- 238000002360 preparation method Methods 0.000 title claims abstract description 23
- 239000002245 particle Substances 0.000 claims abstract description 24
- 238000001237 Raman spectrum Methods 0.000 claims abstract description 12
- 239000013543 active substance Substances 0.000 claims abstract description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 45
- 229910001416 lithium ion Inorganic materials 0.000 claims description 45
- 239000002994 raw material Substances 0.000 claims description 39
- 239000007773 negative electrode material Substances 0.000 claims description 36
- 229910002804 graphite Inorganic materials 0.000 claims description 24
- 239000010439 graphite Substances 0.000 claims description 24
- 239000011230 binding agent Substances 0.000 claims description 18
- 239000006258 conductive agent Substances 0.000 claims description 15
- 229910052799 carbon Inorganic materials 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 14
- 239000002002 slurry Substances 0.000 claims description 11
- 239000007789 gas Substances 0.000 claims description 10
- 230000008569 process Effects 0.000 claims description 9
- 238000002441 X-ray diffraction Methods 0.000 claims description 8
- 239000002270 dispersing agent Substances 0.000 claims description 8
- 238000004458 analytical method Methods 0.000 claims description 7
- 239000002033 PVDF binder Substances 0.000 claims description 6
- 238000000576 coating method Methods 0.000 claims description 6
- 238000009830 intercalation Methods 0.000 claims description 6
- 230000002687 intercalation Effects 0.000 claims description 6
- 229920002981 polyvinylidene fluoride Polymers 0.000 claims description 6
- 239000011248 coating agent Substances 0.000 claims description 5
- 238000001035 drying Methods 0.000 claims description 5
- 239000006229 carbon black Substances 0.000 claims description 4
- 238000002156 mixing Methods 0.000 claims description 4
- 238000005096 rolling process Methods 0.000 claims description 4
- OTYYBJNSLLBAGE-UHFFFAOYSA-N CN1C(CCC1)=O.[N] Chemical compound CN1C(CCC1)=O.[N] OTYYBJNSLLBAGE-UHFFFAOYSA-N 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 13
- 239000010410 layer Substances 0.000 description 43
- 239000006183 anode active material Substances 0.000 description 10
- 238000007873 sieving Methods 0.000 description 8
- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 5
- XUIMIQQOPSSXEZ-UHFFFAOYSA-N Silicon Chemical compound [Si] XUIMIQQOPSSXEZ-UHFFFAOYSA-N 0.000 description 5
- 239000011229 interlayer Substances 0.000 description 5
- 238000011160 research Methods 0.000 description 4
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 3
- 229910013870 LiPF 6 Inorganic materials 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 229910002092 carbon dioxide Inorganic materials 0.000 description 3
- 239000001569 carbon dioxide Substances 0.000 description 3
- 239000011889 copper foil Substances 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 229910003002 lithium salt Inorganic materials 0.000 description 3
- 159000000002 lithium salts Chemical class 0.000 description 3
- 229910021382 natural graphite Inorganic materials 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 229910052710 silicon Inorganic materials 0.000 description 3
- 239000010703 silicon Substances 0.000 description 3
- 239000002356 single layer Substances 0.000 description 3
- 239000002904 solvent Substances 0.000 description 3
- 238000003756 stirring Methods 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 230000005540 biological transmission Effects 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 239000011258 core-shell material Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 2
- 238000000921 elemental analysis Methods 0.000 description 2
- BNKAXGCRDYRABM-UHFFFAOYSA-N ethenyl dihydrogen phosphate Chemical compound OP(O)(=O)OC=C BNKAXGCRDYRABM-UHFFFAOYSA-N 0.000 description 2
- 230000002349 favourable effect Effects 0.000 description 2
- 239000012530 fluid Substances 0.000 description 2
- 230000006872 improvement Effects 0.000 description 2
- -1 lithium hexafluorophosphate Chemical compound 0.000 description 2
- 239000011302 mesophase pitch Substances 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 239000004005 microsphere Substances 0.000 description 2
- 239000003960 organic solvent Substances 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 230000002441 reversible effect Effects 0.000 description 2
- 239000011863 silicon-based powder Substances 0.000 description 2
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910012851 LiCoO 2 Inorganic materials 0.000 description 1
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 1
- 238000004220 aggregation Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
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- 150000001721 carbon Chemical group 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000011246 composite particle Substances 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000010438 heat treatment Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 1
- 229910021437 lithium-transition metal oxide Inorganic materials 0.000 description 1
- 239000000203 mixture Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000009827 uniform distribution Methods 0.000 description 1
- 230000037303 wrinkles Effects 0.000 description 1
Classifications
-
- 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
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/133—Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1393—Processes of manufacture of electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
-
- 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
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- Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Inorganic Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a graphene anode material, a preparation method and application thereof, wherein the Raman spectrum I D/IG of the graphene anode material meets the requirement that I D/IG is less than or equal to 0.1 and less than or equal to 2, and the average particle size of the graphene anode material is 500-2500 nm. The graphene material can be directly used as a negative electrode active substance, and can remarkably improve the performances of a negative electrode, a battery, and the like.
Description
Technical Field
The invention relates to a graphene anode material, a preparation method and application thereof, and belongs to the field of carbon materials and application thereof.
Background
The lithium ion battery has the advantages of high energy density, long cycle life, strong adaptability to the external environment and the like, and is widely applied to the fields of portable electronic equipment, new energy automobiles and the like. The lithium ion battery mainly comprises a positive electrode, a negative electrode and electrolyte, wherein a common positive electrode material mainly comprises lithium transition metal oxide, such as lithium iron phosphate (LiFePO 4), lithium cobaltate (LiCoO 2), ternary materials and the like, and a common negative electrode material mainly comprises graphite, such as natural graphite and the like. For the negative electrode, graphite can provide lower and smooth working voltage, and has long cycle life and high coulombic efficiency, but has lower theoretical capacity, namely 372mA h g -1, which greatly limits the improvement of electrochemical performance of the lithium ion battery (Journal of ENERGY CHEMISTRY 2020;49; 233-242). Therefore, developing high-performance anode materials is an effective way to optimize the performance of lithium ion batteries and promote the development of lithium ion batteries to the application of electric equipment.
Graphene is a novel carbon nanomaterial with a two-dimensional structure, is considered to be the thinnest material with the greatest strength at present, and has great application potential in the aspect of electrode materials. The current graphene is usually compounded with substances such as silicon and the like to form a composite material and then is applied to a battery cathode so as to ensure the capacity, the circularity and other performances of the battery, for example, patent document CN102306757A discloses a lithium ion battery silicon graphene composite cathode material which consists of silicon powder, graphene and amorphous carbon, wherein the graphene forms a three-dimensional conductive network with an internal cavity, and the silicon powder is wrapped in the internal cavity to form spherical or spheroidal composite particles; CN109592674a discloses a graphene anode material, which comprises graphene, soluble mesophase pitch and mesophase micron-sized carbon microspheres, wherein the soluble mesophase pitch is coated on the surfaces of the mesophase micron-sized carbon microspheres to form core-shell particles, and the core-shell particles are distributed in the graphene. Therefore, the development of a novel graphene material, which improves the performance of the graphene material as a negative electrode active material, has an important meaning for improving the performances such as the circularity of a negative electrode and a battery, and is an important subject faced by the person skilled in the art.
Disclosure of Invention
The invention provides a graphene anode material, a preparation method and application thereof, wherein the graphene anode material can be directly used as an anode active material, can obviously improve the performances of an anode, a battery, and the like, and effectively overcomes the defects existing in the prior art.
In one aspect of the invention, a graphene anode material is provided, wherein a Raman spectrum I D/IG of the graphene anode material meets 0.1-2 of I D/IG; the average particle size of the graphene anode material is 500-2500 nm.
According to an embodiment of the present invention, the X-ray diffraction (XRD) analysis result of the graphene anode material shows that: the diffraction angle 2 theta of the (002) interlayer distance is 23-25 degrees; and/or the specific surface area of the graphene anode material is 1m 2/g～5m2/g; and/or, the carbon content of the graphene anode material is not less than 99.99%; and/or the graphene anode material comprises graphene with the number of layers of 1-10.
In another aspect of the present invention, a preparation method of the graphene anode material is provided, including: and crushing the graphene raw material by adopting an airflow crusher to obtain the graphene anode material.
According to one embodiment of the invention, in the crushing treatment process, the rotating speed of the jet mill is 100-50000r/min; and/or the time of the crushing treatment is 1-48h.
According to an embodiment of the present invention, the method further includes a preparation process of a graphene raw material, the preparation process of the graphene raw material including: adding a graphite raw material into a reaction kettle, and introducing gas into the reaction kettle until the gas introduced into the reaction kettle is in a supercritical state, so that the graphite raw material undergoes intercalation reaction in the supercritical state; after 120+/-50 minutes of reaction, the reaction is finished, and the pressure of the reaction kettle is relieved, so that the reacted graphite raw material is stripped, and the graphene raw material is obtained.
In another aspect of the present invention, there is provided a negative electrode sheet including a negative electrode current collector and a negative electrode active material layer on a surface of the negative electrode current collector, the negative electrode active material layer including a negative electrode active material including the above graphene negative electrode material, a conductive agent, and a binder.
According to an embodiment of the present invention, in the anode active material layer, the mass content of the anode active material is 50% to 94%.
According to an embodiment of the present invention, the conductive agent includes carbon black; and/or, in the negative electrode active material layer, the mass content of the conductive agent is 1.5% -45.5%; and/or the binder comprises polyvinylidene fluoride; in the negative electrode active material layer, the mass content of the binder is 4.5-45.5%.
In another aspect of the present invention, a method for preparing the negative electrode sheet is provided, including: mixing the negative electrode active material, the conductive agent, the binder and the dispersing agent to prepare slurry; the dispersant comprises nitrogen methyl pyrrolidone; and (3) coating the slurry on the surface of a current collector, and drying and rolling to form a negative electrode active material layer to obtain the negative electrode sheet.
In another aspect of the present invention, a lithium ion battery is provided, including the above-mentioned negative electrode sheet.
According to the invention, the I D/IG of the graphene anode material meets 0.1- D/IG -2, has proper defect density and small particle size, and the ultra-fine graphene (namely the graphene anode material) with the characteristics is introduced into the anode piece as an anode active material, so that the anode piece is beneficial to the intercalation and deintercalation of lithium ions, has good energy storage capacity for the lithium ions, has the advantages of good conductivity, mechanical property, high capacity and the like, can be directly used as the anode active material, does not need to be compounded with materials such as silicon and the like, is more convenient to use, can remarkably improve the capacity, the circularity and the like of the anode and a battery, and researches show that the battery adopting the graphene anode material as the anode active material has wider voltage platform and excellent multiplying power performance, can provide lower and stable working voltage, and has high reversible capacity (under the condition of 200mAg -1, the reversible capacity can reach more than 542mA g -1) at different current densities; in addition, the graphene anode material provided by the invention has the advantages of simple preparation process, high efficiency and the like, and has important significance for practical industrial application.
Drawings
Fig. 1 is a scanning electron microscope image of the graphene anode material prepared in example 1;
fig. 2 is a graph of the rate performance of the lithium ion battery of example 1;
FIG. 3 is a graph showing the cycling performance of the lithium ion battery of example 1 at a current of 400mA g -1;
Fig. 4 is a graph showing the rate performance of a lithium ion battery using the graphene anode material of example 2, graphite, and conventional graphene as anode active materials, respectively;
Fig. 5 is a charge-discharge graph of a lithium ion battery employing the graphene anode material of example 2, graphite, and conventional graphene as anode active materials, respectively, at a current density of 200mA g -1;
fig. 6 is a transmission electron microscope image of the graphene anode material prepared in example 3;
fig. 7 is a graph of the rate performance of the lithium ion battery of example 3;
Fig. 8 is a charge-discharge curve of the lithium ion battery of example 3 at 600mA g -1;
Fig. 9 is a charge-discharge curve of the lithium ion battery of example 3 at 800mA g -1;
FIG. 10 is a Raman spectrum of the graphene anode material prepared in example 3;
Fig. 11 is an X-ray diffraction (XRD) pattern of the graphene anode material prepared in example 2.
Detailed Description
The present invention will be described in further detail below for the purpose of better understanding of the aspects of the present invention by those skilled in the art. The following detailed description is merely illustrative of the principles and features of the present invention, and examples are set forth for the purpose of illustration only and are not intended to limit the scope of the invention. All other embodiments, which can be made by those skilled in the art based on the examples of the invention without making any inventive effort, are intended to be within the scope of the invention.
According to the graphene anode material provided by the invention, the Raman spectrum I D/IG of the graphene anode material meets the requirement that I D/IG is less than or equal to 0.1 and less than or equal to 2; the average particle size of the graphene anode material is 500-2500 nm.
Specifically, raman spectrum I D/IG is the ratio of peak height I 1350(ID) of 1350cm -1 to peak height I 1580(IG) of 1580cm -1 in the raman spectrum of the graphene anode material. For example, I D/IG is, for example, a range of 0.1, 0.3, 0.5, 0.7, 0.9, 1.2, 1.5, 1.8, 2, or any two thereof, with I D/IG < 2 generally preferred.
For example, the average particle size of the graphene anode material may be in the range of 500nm, 1000nm, 1500nm, 2000nm, 2500nm, or any two of these. In specific implementation, the average particle size of the graphene anode material can be measured by using a conventional particle size tester in the field such as a nanometer laser particle sizer.
In general, the X-ray diffraction (XRD) analysis result of the graphene anode material shows that the diffraction angle 2θ of the (002) layer spacing is 5 ° to 90 ° (i.e., the XRD ray diffraction range is 5 ° to 90 °), for example, 5 °, 10 °, 15 °, 20 °, 23 °, 25 °, 30 °, 40 °, 50 °, 60 °, 70 °, 80 °, 90 °, or a range composed of any two of them.
Through further research, the graphene anode material has good crystallinity, and an X-ray diffraction (XRD) analysis result shows that the graphene anode material has a diffraction angle of superfine graphene, namely, a diffraction angle 2 theta of (002) interlayer spacing is 23-25 degrees, and the graphene anode material is favorable for further improving the performance of the graphene anode material serving as an anode active substance.
In some embodiments, the graphene anode material has a specific surface area in the range of 1m 2/g～5m2/g, e.g., 1m 2/g、2m2/g、3m2/g、4m2/g、5m2/g, or any two of these.
In some embodiments, the carbon content of the graphene anode material is not less than 99.99%, and the balance may be hydrogen and other components. In specific implementation, elemental analysis can be performed on the graphene anode material to determine the carbon content therein, and the elemental analysis can be performed by using instruments and methods conventional in the art, which are not particularly limited.
The graphene is composed of single-layer carbon atom layers, belongs to a two-dimensional crystal structure, and specifically can comprise at least one of graphene with 1-10 layers (namely, the graphene has a layered structure formed by 1-10 layers of single-layer graphene), namely, the graphene anode material comprises graphene with 1 layer, graphene with 2 layers, graphene with 3 layers, graphene with 4 layers, graphene with 5 layers, graphene with 6 layers, graphene with 7 layers, graphene with 8 layers, graphene with 9 layers and graphene with 10 layers, and most of the graphene layers are concentrated in 1-4 layers.
Specifically, the graphene anode material may be graphene with the number of layers of n (i.e., consisting of n layers of single-layer graphites), 1.ltoreq.n.ltoreq.10, n being, for example, 1, 2, 3, 4, 5,6,7, 8, 9, 10 or a range of any two of them, preferably 1.ltoreq.n.ltoreq.7. The graphene negative electrode material is graphene with n layers, which means that most of the graphene in the graphene negative electrode material has n layers, that is, most of the graphene is graphene with n layers, and due to factors such as preparation process errors, few or very few graphene with n layers may exist.
The preparation method of the graphene anode material comprises the following steps: and crushing the graphene raw material by adopting an airflow crusher to obtain the graphene anode material. According to the research of the invention, the graphene raw material can be crushed by the preparation method, so that graphene with smaller particle size (namely the graphene anode material) can be obtained, a certain stripping effect is realized, the number of layers and thickness of the obtained graphene with smaller particle size are reduced, more importantly, the surface smoothness of the obtained graphene can be ensured, the obtained graphene has proper defect density, meanwhile, the integrity of the lamellar structure of the graphene anode material is ensured, and the research shows that the surface of the prepared graphene anode material is smooth and basically has no phenomena of interlayer fracture, wrinkle and the like. In addition, the preparation method has the advantages of simple operation, low cost and the like.
In general, in the crushing treatment process, the rotating speed of the jet mill is 100-50000r/min, namely, the graphene raw material is stirred and crushed under the condition that the rotating speed is 100-50000r/min, so that the graphene anode material is prepared. The rotational speed of the jet mill is, for example, 100r/min、1000r/min、3000r/min、5000r/min、7000r/min、10000r/min、20000r/min、30000r/min、40000r/min、50000r/min or a range of any two of these. The time of the pulverization treatment may be generally in the range of 1 to 48 hours, for example, 1 hour, 5 hours, 10 hours, 20 hours, 30 hours, 40 hours, 48 hours, or any two thereof.
In some embodiments, the number of times of the crushing treatment may be 5 to 15 times, which is more favorable for obtaining the graphene anode material with small particle size. In the specific implementation, the graphene raw material is added into an airflow crusher to be crushed, then the crushed product is sieved to remove large particulate matters in the crushed product, and the obtained small particulate product is added into the airflow crusher to be crushed, and the crushing-sieving process is repeated for 5-15 times, so that the graphene anode material is prepared. The mesh number of the screen used for sieving can be generally 200-10000 meshes, in the process of smashing and sieving, the screen with the mesh number of m1 is firstly adopted for sieving, large particles are removed, the obtained primary small particles are smashed again, then the screen with the mesh number of m2 is adopted for sieving, the large particles are removed, the obtained secondary small particles are smashed again, then the screen with the mesh number of m3 is adopted for sieving … … and so on, until the smashing and sieving process is repeated, and the graphene anode material is obtained, wherein m1, m2 and m3 … … are sequentially increased (namely the pore diameters of the used screens are sequentially reduced).
In addition, in the concrete implementation, the material to be crushed (such as the graphene raw material) can be added into the jet mill for crushing for 3-6 times, namely, the material to be crushed can be averagely divided into 3-6 parts, and the materials are respectively added into the jet mill for crushing treatment.
In the present invention, the graphene raw material may be prepared by using supercritical fluid, and in some preferred embodiments, the preparation process of the graphene raw material includes: adding a graphite raw material into a reaction kettle, and introducing gas into the reaction kettle until the gas introduced into the reaction kettle is in a supercritical state, so that the graphite raw material undergoes intercalation reaction in the supercritical state; and after the reaction is finished, the reaction kettle is depressurized to strip the reacted graphite raw material, so as to obtain the graphene raw material. Alternatively, the temperature in the supercritical state may be 50±5 ℃, and the pressure may be such that the gas is in the supercritical state, the gas may include carbon dioxide, and the graphite raw material may include natural graphite.
In the preparation process, the number of layers of the graphene raw material used can be 1-10, and the carbon content of the graphene raw material can be not less than 99.9% (generally, the carbon content of the prepared graphene anode material is basically equal to that of the graphene raw material used).
The negative electrode sheet comprises a negative electrode current collector and a negative electrode active material layer positioned on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, a conductive agent and a binder, and the negative electrode active material comprises the graphene negative electrode material. Wherein, the negative electrode active material may be all graphene negative electrode materials.
In some embodiments, in the anode active material layer, the mass content of the anode active material is 50% to 94%, for example, 50%, 60%, 70%, 80%, 90%, 94% or a range of any two of them, the mass content of the conductive agent may be 1.5% to 45.5%, and the mass content of the binder may be 4.5% to 45.5%.
Specifically, the conductive agent may include carbon black, and the binder may include polyvinylidene fluoride (PVDF), which is more beneficial to matching with the graphene anode material described above, and optimizing the anode sheet performance. However, the present invention is not limited thereto, and other materials such as conventional conductive agents and binders in the art may be used.
Specifically, in the above-mentioned negative electrode sheet, the negative electrode active material layers may be provided on both the front and back surfaces of the negative electrode current collector, or the negative electrode active material layers may be provided on one surface of the negative electrode current collector, and may be selected as required in specific implementation. The negative electrode current collector may be a conventional negative electrode current collector in the art such as copper foil, and the present invention is not particularly limited thereto.
The preparation method of the negative plate comprises the following steps: mixing a negative electrode active material, a conductive agent, a binder, and a dispersant, wherein the dispersant comprises N-methyl pyrrolidone (NMP), to prepare a slurry; and (3) coating the slurry on the surface of a current collector, and drying and rolling to form a negative electrode active material layer to obtain a negative electrode plate. According to the process, the negative plate is prepared by a coating method, NMP is used as a dispersing agent (or solvent), so that components such as a graphene negative electrode material and a conductive agent are uniformly dispersed, and phenomena such as particle aggregation are avoided, so that the negative plate with excellent performance is prepared. In particular, the binder may be dissolved in a solvent, and then the obtained binder solution may be mixed with materials such as a negative electrode active material, a conductive agent, a dispersing agent, etc. to prepare a slurry, and the mass concentration of the binder in the binder solution may be generally 5 to 9%, and the solvent for dissolving the binder may include NMP, etc.
Wherein, the slurry can be coated on the surface of the negative electrode current collector by adopting a conventional coating device in the field such as a knife coater, and the slurry can be dried at 80-120 ℃ after being coated on the surface of the negative electrode current collector, and then rolled and cut into sheets meeting the requirements of shape and size by adopting a tablet press, and can be further dried at 80-120 ℃ to obtain the negative electrode sheet.
The lithium ion battery comprises the negative plate. The lithium ion battery may be, for example, but not limited to, a button cell battery, which may be manufactured according to a conventional method in the art.
The lithium ion battery further comprises a positive plate and a diaphragm, wherein the diaphragm is positioned between the positive plate and the negative plate and is used for spacing the positive plate and the negative plate. The present invention may employ a positive electrode sheet, such as a lithium sheet, and a separator, such as a commercially available celgard2400 separator, etc., which are conventional in the art, and may be commercially available or self-made.
In addition, the lithium ion battery further contains an electrolyte, and the electrolyte may include an organic solvent and a lithium salt, wherein the organic solvent may include vinyl phosphate and/or dimethyl carbonate, the lithium salt may include lithium hexafluorophosphate (LiPF 6), and the concentration of the lithium salt in the electrolyte is, for example, 0.8 to 1.5mol/L, but the composition of the electrolyte is not limited thereto.
For the purpose of promoting an understanding of the principles of the invention, reference will now be made in detail to specific examples, some but not all of which are illustrated in the accompanying drawings. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In the following examples, the battery performance was tested by using a new wilt charge and discharge tester, including a rate performance test, a charge and discharge characteristic test, a cycle performance test, etc., and the constant current charge and discharge test was performed with a voltage range of 0.01 to 3V and a current density range of 200 to 1000mA g -1.
Example 1
1. Supercritical fluid preparation of graphene raw materials: adding natural graphite into a reaction kettle, introducing carbon dioxide into the reaction kettle, heating to about 50 ℃, controlling the pressure to enable the carbon dioxide introduced into the reaction kettle to be in a supercritical state, enabling graphite raw materials to conduct intercalation reaction in the supercritical state, after the reaction is completed for about 120min, enabling the reaction kettle to release pressure, and stripping the reacted graphite raw materials to obtain the graphene raw materials.
2. Preparation of graphene anode material
(1) Adding 30g of graphene raw material into an airflow pulverizer for 5-6 times, stirring and pulverizing at a rotating speed of 500-3000r/min for 24-30h to obtain a pulverized product;
(2) Sieving the crushed product with a sieve with mesh number of 2000-6000 meshes, and collecting small particle products passing through the sieve;
(3) Repeating the step (1) and the step (2) for 9 times (namely, crushing 10 times) to obtain the graphene anode material.
The raman spectrum I D/IG =0.9 of the graphene material is tested, the average particle size is about 2600nm, and the xrd analysis result shows that: diffraction angle with ultrafine graphene, i.e., (002) layer spacing, 2θ=25.9°; the specific surface area is 1.8m 2/g, the number of layers is 4, and the carbon content is more than 99.99%.
In addition, the graphene anode material is analyzed by adopting a Scanning Electron Microscope (SEM), and the result is shown in fig. 1, so that the characteristics of smooth and even surface, uniform distribution and the like of the graphene can be seen.
3. Preparation of negative electrode sheet
Mixing the graphene anode material, carbon black and PVDF solution (the PVDF mass concentration is 7%) with NMP, and uniformly stirring by a magnetic stirrer (the stirring time is about 9 h) to prepare slurry;
And coating the slurry on the surface of the copper foil by adopting a knife coater, then putting the copper foil into an oven for drying at 100 ℃, then adopting a tablet press for rolling and cutting into sheets with the diameter of 13mm, and then drying in a vacuum oven at 80 ℃ for 12 hours to obtain the negative electrode sheet.
4. Preparation of lithium ion batteries
The lithium sheet is used as a positive electrode sheet (reference electrode), and the positive electrode sheet, a celgard2400 diaphragm and a negative electrode sheet are formed into a button cell in a glove box filled with argon, wherein electrolyte used by the button cell consists of vinyl phosphate, dimethyl carbonate and LiPF 6, and the concentration of LiPF 6 is 1mol/L.
5. Lithium ion battery performance test
(1) The rate performance graph of the lithium ion battery is shown in fig. 2, and it can be seen that the capacity of the lithium ion battery at 200mA g -1 current density is about 542mA h g -1.
(2) The graph of the cycle performance of the lithium ion battery at the current of 400mA g -1 is shown in figure 3, and it can be seen that the capacity of the lithium ion battery for 100 circles at the current density of 400mA g -1 is 431mA h g -1, and the capacity of the lithium ion battery after the lithium ion battery is cycled is not attenuated, so that the lithium ion battery has good cycle performance.
Example 2
Example 2 is different from example 1 in that in step (3) of preparing a graphene anode material, steps (1) and (2) are repeated 12 times in total (i.e., crushed 13 times in total), and the other conditions are the same as example 1.
Through testing, the Raman spectrum I D/IG =0.6 of the graphene anode material has an average particle size of about 800nm; XRD analysis results showed that: diffraction angle 2 θ=25.4° having an ultrafine graphene, i.e., (002) layer spacing (XRD pattern thereof is shown in fig. 11); the specific surface area is 2.7m 2/g, the number of layers is 3, and the carbon content is more than 99.99%.
The rate performance curve of the lithium ion battery of example 2 is shown in fig. 4 (see the curve corresponding to the graphene anode material in fig. 4), and the charge and discharge curves of the lithium ion battery under the current density condition of 200mA g -1 are shown in fig. 5 (see the curve corresponding to the graphene anode material in fig. 5);
In addition, the graphene anode material in the embodiment 1 is replaced by conventional coarse graphene, a lithium ion battery is prepared according to the process of the embodiment, the measured rate performance curve of the lithium ion battery is shown in fig. 4 (see curve corresponding to conventional graphene in fig. 4), and the charge and discharge curve of the lithium ion battery under the current density condition of 200mA g -1 is shown in fig. 5 (see curve corresponding to conventional graphene in fig. 5); wherein, the raman spectrum I D/IG =2 of the crude graphene has an average particle size of about 3000nm to 30000nm, and the xrd analysis result shows that: it has a diffraction angle of coarse graphene, i.e., (002) diffraction angle of interlayer spacing 2θ=26°; the specific surface area is 1.5m 2/g, the number of layers is 8-15, and the carbon content is 99.99%;
A lithium ion battery was prepared according to the procedure of example 1 by replacing the graphene anode material in example 1 with commercial graphite, and the rate performance curve of the lithium ion battery was measured and shown in fig. 4 (see the curve corresponding to graphite in fig. 4), and the charge and discharge curves of the lithium ion battery under the current condition of 200mA g -1 are shown in fig. 5 (see the curve corresponding to graphite in fig. 5).
As can be seen from fig. 4 and 5, the capacity of the lithium ion battery of example 2 under different current density conditions and different cycle times is significantly higher than that of the lithium ion battery using graphite and conventional graphite, and the lithium ion battery of example 2 has a wider plateau under a current condition of 200mA g -1 and a voltage of 0.5V.
Example 3
Example 2 is different from example 1 in that in step (3) of preparing a graphene anode material, steps (1) and (2) are repeated 14 times in total (i.e., crushed 15 times in total), and the remaining conditions are the same as example 1.
The raman spectrum of the graphene material is shown in fig. 10, the raman spectrum I D/IG =0.2, the average particle size is about 500nm, and the xrd analysis result shows that: diffraction angle with ultrafine graphene, i.e., (002) diffraction angle of interlayer spacing 2θ=25°; the specific surface area is 3.9m 2/g, the number of layers is 2, and the carbon content is more than 99.99%.
A Transmission Electron Microscope (TEM) image of the graphene anode material of example 3 was measured and shown in fig. 6, and it can be seen from fig. 6 that the surface of the graphene anode material is flat and has a complete lamellar structure (the structures of the graphene anode materials of examples 1 and 2 are similar to those of the graphene anode material of example 3).
The rate performance curve of the lithium ion battery of example 3 is shown in fig. 7, the charge-discharge curve of the lithium ion battery under the current density condition of 600mA g -1 is shown in fig. 8, the charge-discharge curve under the current density condition of 800mA g -1 is shown in fig. 9, the specific capacities of the lithium ion battery under the current of 600mA g -1、800mA g-1 are about 135mA h g -1 and 107mA h g -1 respectively, and the lithium ion battery still has a wider 0.5V voltage platform under high current.
The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (7)
1. A graphene anode material is characterized in that a Raman spectrum I D/IG of the graphene anode material meets 0.1-0. D/IG -0.9; the average particle size of the graphene anode material is 500-2500 nm; the X-ray diffraction (XRD) analysis result of the graphene anode material shows that: the diffraction angle 2 theta of the (002) layer spacing is 23-25 degrees; the specific surface area of the graphene anode material is 1m 2/g ~5m2/g; the carbon content of the graphene anode material is not less than 99.99%; the graphene anode material comprises graphene with the number of layers of 1-10;
the graphene anode material is directly used for anode active substances;
the preparation process of the graphene anode material comprises the following steps:
Crushing a graphene raw material by adopting an airflow crusher to obtain the graphene anode material; in the crushing treatment process, the rotating speed of the jet mill is 100-50000r/min; and/or the time of the crushing treatment is 1-48h;
The preparation process of the graphene raw material comprises the following steps: adding a graphite raw material into a reaction kettle, and introducing gas into the reaction kettle until the gas introduced into the reaction kettle is in a supercritical state, so that the graphite raw material undergoes intercalation reaction in the supercritical state; after 120+/-50 minutes of reaction, the reaction is finished, and the pressure of the reaction kettle is relieved, so that the reacted graphite raw material is stripped, and the graphene raw material is obtained.
2. The method for preparing the graphene anode material according to claim 1, comprising: crushing a graphene raw material by adopting an airflow crusher to obtain the graphene anode material; in the crushing treatment process, the rotating speed of the jet mill is 100-50000r/min; and/or the time of the crushing treatment is 1-48h;
The preparation process of the graphene raw material comprises the following steps: adding a graphite raw material into a reaction kettle, and introducing gas into the reaction kettle until the gas introduced into the reaction kettle is in a supercritical state, so that the graphite raw material undergoes intercalation reaction in the supercritical state; after 120+/-50 minutes of reaction, the reaction is finished, and the pressure of the reaction kettle is relieved, so that the reacted graphite raw material is stripped, and the graphene raw material is obtained.
3. A negative electrode sheet comprising a negative electrode current collector and a negative electrode active material layer on the surface of the negative electrode current collector, wherein the negative electrode active material layer comprises a negative electrode active material, a conductive agent and a binder, and the negative electrode active material comprises the graphene negative electrode material of claim 1.
4. The negative electrode sheet according to claim 3, wherein the mass content of the negative electrode active material in the negative electrode active material layer is 50% to 94%.
5. The negative electrode sheet according to claim 3 or 4, wherein,
The conductive agent includes carbon black; and/or the number of the groups of groups,
In the negative electrode active material layer, the mass content of the conductive agent is 1.5% -45.5%; and/or the number of the groups of groups,
The binder comprises polyvinylidene fluoride;
in the negative electrode active material layer, the mass content of the binder is 4.5% -45.5%.
6. The method for producing a negative electrode sheet according to any one of claims 3 to 5, comprising:
mixing the negative electrode active material, the conductive agent, the binder and the dispersing agent to prepare slurry; the dispersant comprises nitrogen methyl pyrrolidone;
and (3) coating the slurry on the surface of a current collector, and drying and rolling to form a negative electrode active material layer to obtain the negative electrode sheet.
7. A lithium ion battery comprising the negative electrode sheet of any one of claims 3-5.
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