CN112694086A - Modified graphite material, preparation method and application thereof, and lithium ion battery - Google Patents
Modified graphite material, preparation method and application thereof, and lithium ion battery Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical class [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 117
- 239000007770 graphite material Substances 0.000 title claims abstract description 54
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 title claims abstract description 23
- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 23
- 238000002360 preparation method Methods 0.000 title claims abstract description 16
- 239000002245 particle Substances 0.000 claims abstract description 39
- 229910002804 graphite Inorganic materials 0.000 claims abstract description 38
- 239000010439 graphite Substances 0.000 claims abstract description 38
- 238000003763 carbonization Methods 0.000 claims abstract description 37
- 229910021389 graphene Inorganic materials 0.000 claims abstract description 30
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims abstract description 22
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims abstract description 22
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims abstract description 22
- 238000010438 heat treatment Methods 0.000 claims abstract description 20
- 238000000576 coating method Methods 0.000 claims abstract description 18
- 239000002002 slurry Substances 0.000 claims abstract description 18
- 239000011248 coating agent Substances 0.000 claims abstract description 17
- 238000005087 graphitization Methods 0.000 claims abstract description 13
- 239000007864 aqueous solution Substances 0.000 claims abstract description 11
- 239000002994 raw material Substances 0.000 claims abstract description 9
- 230000004927 fusion Effects 0.000 claims description 26
- 239000012298 atmosphere Substances 0.000 claims description 24
- 238000000034 method Methods 0.000 claims description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 18
- 238000003756 stirring Methods 0.000 claims description 13
- 230000001681 protective effect Effects 0.000 claims description 8
- 238000001816 cooling Methods 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 6
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 6
- 239000007773 negative electrode material Substances 0.000 claims description 6
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 6
- 230000008569 process Effects 0.000 claims description 6
- 239000002006 petroleum coke Substances 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- 239000008367 deionised water Substances 0.000 claims description 4
- 229910021641 deionized water Inorganic materials 0.000 claims description 4
- 239000010941 cobalt Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 229910052742 iron Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 239000005662 Paraffin oil Substances 0.000 claims description 2
- 239000002480 mineral oil Substances 0.000 claims description 2
- 235000010446 mineral oil Nutrition 0.000 claims description 2
- 239000003921 oil Substances 0.000 claims description 2
- 230000000052 comparative effect Effects 0.000 description 24
- 238000012360 testing method Methods 0.000 description 7
- 229910021383 artificial graphite Inorganic materials 0.000 description 6
- 230000000694 effects Effects 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 5
- 239000000463 material Substances 0.000 description 4
- 239000006185 dispersion Substances 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 238000007796 conventional method Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
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- 238000012986 modification Methods 0.000 description 2
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- 239000003208 petroleum Substances 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 239000007858 starting material Substances 0.000 description 2
- 238000010998 test method Methods 0.000 description 2
- 238000001291 vacuum drying Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- WHNWPMSKXPGLAX-UHFFFAOYSA-N N-Vinyl-2-pyrrolidone Chemical compound C=CN1CCCC1=O WHNWPMSKXPGLAX-UHFFFAOYSA-N 0.000 description 1
- 229920003081 Povidone K 30 Polymers 0.000 description 1
- 229910003481 amorphous carbon Inorganic materials 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000011329 calcined coke Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 230000006866 deterioration Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000007789 gas Substances 0.000 description 1
- 229910021469 graphitizable carbon Inorganic materials 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- VNWKTOKETHGBQD-UHFFFAOYSA-N methane Chemical compound C VNWKTOKETHGBQD-UHFFFAOYSA-N 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000011163 secondary particle Substances 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
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Images
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/205—Preparation
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/20—Graphite
- C01B32/21—After-treatment
-
- 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
- H01M4/36—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
- 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
-
- 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 discloses a modified graphite material, a preparation method and application thereof, and a lithium ion battery. The preparation method of the modified graphite material comprises the following steps: s1, preparing graphite particles: sequentially carrying out heat treatment and graphitization on a graphite raw material to obtain graphite particles; s2, primary coating: fusing the graphite particles and the oily graphene slurry, and performing first carbonization to obtain primary coated graphite particles; s3, secondary coating: and fusing the primary coated graphite particles with a polyvinylpyrrolidone aqueous solution, and performing second carbonization to obtain the modified graphite material. The lithium ion battery prepared by the modified graphite material has high discharge capacity and excellent rate capability and impedance performance.
Description
Technical Field
The invention relates to a modified graphite material, a preparation method and application thereof, and a lithium ion battery.
Background
With the exhaustion of energy and the growing deterioration of the environment, it is increasingly important to find alternative clean energy. The lithium ion battery as a new generation of energy storage material has the advantages of light weight, long service life, high specific energy density, no pollution, no memory effect and the like, and is widely applied to electronic equipment such as mobile phones, computers, digital cameras and the like. The lithium ion battery mainly comprises a positive electrode material, a negative electrode material, a diaphragm and an electrolyte, and the performance of the negative electrode material determines the performance of the battery. The artificial graphite is the most extensive material in the cathode material, and has the advantages of abundant reserves, low price, stable electrochemical performance, actual energy density close to theoretical energy density and the like. Generally, the artificial graphite material of the graphitized product has the defects of poor rate capability and impedance performance, and has a limited application prospect, and the purpose of improving the rate is achieved by adopting amorphous carbon coating. At present, most of the conventional artificial graphite materials are coated once, and the capacity of the artificial graphite materials is slightly reduced compared with that of graphitized products. Therefore, the method has great application prospect in preparing products with higher capacity and better rate performance.
Disclosure of Invention
The invention provides a modified graphite material, a preparation method and application thereof and a lithium ion battery, aiming at overcoming the defects of low capacity, poor rate capability and poor impedance performance of an artificial graphite material when the artificial graphite material is used for the lithium ion battery in the prior art. The lithium ion battery prepared by the modified graphite material has high discharge capacity and excellent rate capability and impedance performance.
In order to achieve the purpose, the invention adopts the following technical scheme:
the invention provides a preparation method of a modified graphite material, which comprises the following steps:
s1, preparing graphite particles: sequentially carrying out heat treatment and graphitization on a graphite raw material to obtain graphite particles;
s2, primary coating: fusing the graphite particles and the oily graphene slurry, and performing first carbonization to obtain primary coated graphite particles;
s3, secondary coating: and fusing the primary coated graphite particles with a polyvinylpyrrolidone (PVP) aqueous solution, and performing second carbonization to obtain the modified graphite material.
In the present invention, in step S1, the graphite raw material may be a graphitizable carbon material conventional in the art, and is preferably petroleum coke.
In the present invention, in step S1, the particle size D50 of the graphite raw material is preferably 8 to 12 μm, for example, 10 μm. The particle size of the graphite starting material is generally obtained by comminution, which may be carried out in a manner and with equipment conventional in the art. The crushing apparatus is preferably a roll mill.
In the present invention, in step S1, the temperature of the heat treatment may be 550 to 650 ℃. The time of the heat treatment can be 8-22 h. Preferably, the temperature of the heat treatment is 630 ℃, and the time of the heat treatment is 8 h.
The heat treatment is preferably carried out under a protective atmosphere. The protective atmosphere may be an inert atmosphere or a nitrogen atmosphere.
The heat treatment may be carried out using equipment conventional in the art, preferably a horizontal coating kettle. The purpose of the heat treatment is to remove volatile components in the graphite raw material and to achieve surface modification. The surface modification means that the surface of the crushed graphite raw material is rounded through heat treatment, so that the shape characteristics of the tip are reduced, and the shape of the tip is better.
In the present invention, in step S1, the graphitization may be performed by using an apparatus conventional in the art, preferably an acheson graphitization furnace.
The graphitization temperature can be 2800-3200 ℃. The graphitization time can be 20-60 h. Preferably, the graphitization temperature is 3000 ℃, and the graphitization time is 30 h.
In the present invention, in step S2, the oily graphene paste may be a commercially available product that is conventional in the art, such as oily graphene paste available from ningbo graphene technologies, ltd.
The oily graphene slurry preferably meets the following technical parameters: the water content is less than or equal to 1%, the particle size D50 of the graphene is 7-14 mu m, the viscosity is less than or equal to 3500mPas, the iron content is less than or equal to 10PPm, the cobalt content is less than or equal to 5PPm, and the nickel content is less than or equal to 5 PPm.
The content of graphene in the oily graphene slurry is preferably 5.0 ± 0.2 wt%.
The oily graphene slurry may also be prepared using a method conventional in the art. The preparation method of the graphene slurry generally comprises the following steps: heating graphene and a solvent in a water bath and stirring. The temperature of the water bath is preferably between 40 ℃ and 80 ℃, more preferably between 60 ℃ and 70 ℃. The stirring time is preferably 60 to 90 min. The solvent may be a solvent conventionally used for oily graphene slurry, such as white oil, paraffin oil, mineral oil, and the like.
In the present invention, in step S2, the mass ratio of the graphite particles to the oily graphene slurry may be 100: (6-20), preferably 100: 9.
In step S2, the purpose of the fusion is to achieve dispersion and uniform coating of the oily graphene slurry and the graphite particles.
The fusion can be carried out in a fusion machine conventional in the art. The rotating speed of the fusion machine can be 250-1400 r/min. The fusion time can be 8-60 min. Preferably, the rotating speed of the fusion machine is 280r/min, and the fusion time is 20 min. The conditions for the fusion are preferably normal temperature and air atmosphere.
In the present invention, in step S2, the temperature of the first carbonization is preferably 950 to 1350 ℃. The first carbonization time is preferably 0.5 to 24 hours. The first carbonization process preferably comprises a constant temperature of 1150 ℃ for 22 h.
The first carbonization is generally carried out under a protective atmosphere, which may be an inert atmosphere or a nitrogen atmosphere. The first carbonization may be performed in a carbonization apparatus conventional in the art, such as a carbonization furnace, an atmosphere protection high temperature chamber furnace, and the like.
In the present invention, in step S3, the mass ratio of polyvinylpyrrolidone to water in the polyvinylpyrrolidone aqueous solution may be (3 to 8):10, and preferably (5 to 7): 10.
The aqueous polyvinylpyrrolidone solution may be prepared by a method conventional in the art. The method for preparing the aqueous polyvinylpyrrolidone solution generally comprises the following steps: and stirring polyvinylpyrrolidone and water at 80-90 ℃, and cooling. The water is preferably deionized water. The stirring may be carried out by methods conventional in the art, ensuring uniform dispersion of the components. The stirring speed is preferably 60r/min, and the stirring time is preferably 1-2 h. The cooling is generally carried out by naturally cooling to room temperature in the air.
In step S3, the mass ratio of the primary coated graphite particles to the polyvinylpyrrolidone aqueous solution may be 100: (10-20), preferably 100: 15.
In the present invention, in step S3, the purpose of the fusion is to achieve dispersion and uniform coating of the polyvinylpyrrolidone aqueous solution and the primary coated graphite particles. The fusion is performed as described above.
In the present invention, in step S3, the temperature of the second carbonization is preferably 550 to 850 ℃. The second carbonization time is preferably 5 to 30 hours. The second carbonization process preferably comprises a constant temperature of 22h at 700 ℃. The second carbonization is generally carried out under a protective atmosphere, which may be an inert atmosphere or a nitrogen atmosphere. The second carbonization may be performed in a carbonization apparatus conventional in the art, which preferably protects a high temperature box furnace from the atmosphere.
In the present invention, the first carbonization and the second carbonization may be performed in the same apparatus, preferably in an atmosphere-protected high-temperature box furnace.
The invention also provides a modified graphite material which is prepared according to the preparation method of the modified graphite material.
In the present invention, the modified graphite material preferably has the following properties: the particle size is 12-15 mu m; the specific surface area is 3.5-5.5m2(ii)/g; tap density is more than or equal to 0.95g/cm3(ii) a The compacted density is more than or equal to 1.5g/cm3。
The invention also provides a lithium ion battery, and the negative electrode material of the lithium ion battery comprises the modified graphite material. The lithium ion battery preferably has the following properties: the discharge capacity is more than or equal to 360 mAh/g; the first discharge efficiency is more than or equal to 89 percent.
The invention also provides application of the modified graphite material as a negative electrode material in a lithium ion battery.
On the basis of the common knowledge in the field, the above preferred conditions can be combined randomly to obtain the preferred embodiments of the invention.
The reagents and starting materials used in the present invention are commercially available.
The positive progress effects of the invention are as follows:
the modified graphite material is prepared by adopting a secondary coating method, the preparation method is simple, and the method is suitable for mass production. The lithium ion battery prepared by the modified graphite material has high capacity, excellent rate capability and impedance performance and excellent comprehensive performance.
Drawings
Fig. 1 is an SEM image of the modified graphite material obtained in example 1.
Fig. 2 is an ac impedance diagram of a lithium ion battery prepared using the modified graphite material prepared in example 1 in effect example 2.
Fig. 3 is a graph showing the discharge rate performance of a lithium ion battery prepared in effect example 3 using the modified graphite material prepared in example 1.
Detailed Description
The invention is further illustrated by the following examples, which are not intended to limit the scope of the invention. The experimental methods without specifying specific conditions in the following examples were selected according to the conventional methods and conditions, or according to the commercial instructions.
In the following examples and comparative examples:
the petroleum coke is ordinary petroleum calcined coke purchased from Daqing petrochemical division of China Petroleum and gas resources Co.
The oily graphene slurry is purchased from Ningbo yuanxinen graphene science and technology Co., Ltd; the oily graphene slurry meets the following technical parameters: the water content is less than or equal to 1%, the particle size D50 of the graphene is 7-14 mu m, the viscosity is less than or equal to 3500mPas, the iron content is less than or equal to 10PPm, the cobalt content is less than or equal to 5PPm, and the nickel content is less than or equal to 5 PPm; the content of graphene in the oily graphene slurry is 5.0 +/-0.2 wt%.
Polyvinylpyrrolidone was purchased from Shanghai Noita chemical Co., Ltd, and its model number was PVP-K30.
The horizontal coating kettle is purchased from Wuxi Qingxin powder equipment Co., Ltd, and the model is WHR-500L.
The fusion machine is purchased from Sn-free New photo powder science and technology Co., Ltd, and has the model of TF-LS-5 HP.
The atmosphere protection high temperature box furnace is available from Miyaelectric furnace Co., Ltd, Yixing, and has a model of RF-60-13.
Example 1
A preparation method of a modified graphite material comprises the following steps:
s1, preparing graphite particles: crushing petroleum coke to 10 mu m of D50, placing the crushed petroleum coke in a horizontal coating kettle, and carrying out heat treatment for 8h at 630 ℃ under the protection of high-purity nitrogen; then transferring the material to an Acheson graphitizing furnace, and graphitizing for 30h at 3000 ℃ to obtain graphite particles;
s2, primary coating: placing graphite particles and oily graphene slurry (the mass ratio is 100:9) into a fusion machine for fusion, wherein the rotating speed of the fusion machine is 280r/min, and the fusion time is 20 min;
transferring the material to a carbonization furnace in an inert atmosphere for first carbonization, wherein the first carbonization process is constant temperature at 1150 ℃ for 22 hours to obtain primary coated graphite particles;
s3, secondary coating:
adding polyvinylpyrrolidone (PVP) and deionized water (the mass ratio is 7:10) into a 5000mL three-neck flask, heating to 80-90 ℃, stirring at the rotating speed of 60r/min for 2h to ensure that the two components are uniformly dispersed, cooling in air, and pouring out to form a PVP aqueous solution;
placing the primary coated graphite particles and PVP aqueous solution (the mass ratio is 100:15) in a fusion machine for fusion, wherein the rotating speed of the fusion machine is 280r/min, and the fusion time is 20 min;
and transferring the material to an atmosphere protection high-temperature box furnace under inert atmosphere for second carbonization, wherein the second carbonization process is carried out at the constant temperature of 700 ℃ for 22 hours to obtain the modified graphite material.
Example 2
Except in step S3, PVP: the procedure and conditions were the same as in example 1 except that deionized water was 5: 10.
Comparative example 1
Primary-coated graphite particles were prepared as comparative example 1 following steps S1 and S2 in example 1.
Comparative example 2
Graphite particles were obtained as comparative example 2 in accordance with step S1 in example 1.
Effect example 1
The modified graphite materials obtained in examples 1-2 and comparative examples 1-2 were each subjected to the following tests using methods conventional in the art:
(1) the SEM picture of the modified graphite material prepared in example 1 was tested using a scanning electron microscope Phenom XL, and the test results are shown in FIG. 1. As can be seen from fig. 1, the modified graphite material particles have a slightly bonded structure of secondary particles.
(2) The particle size of the modified graphite material was measured using a laser particle size distribution instrument MS3000, and the results are shown in table 1. The particle size of the modified graphite materials in examples 1-2 was slightly increased compared to comparative examples 1-2.
(3) The tap density of the modified graphite material was measured using a tap machine TF-100B, as shown in Table 1. The tap densities of the modified graphite materials of examples 1-2 were comparable and remained at a higher level than those of comparative examples 1-2.
(4) The specific surface area of the modified graphite material was measured by a specific surface area measuring instrument NOVATouch2000, and the measurement results are shown in table 1. The specific surface area of the modified graphite materials in examples 1 to 2 was increased as compared with those in comparative examples 1 to 2.
(5) The compacted density of the modified graphite material was measured using an FT-100F powder auto-compaction densitometer, as shown in Table 1. The modified graphite materials of examples 1-2 had slightly lower compacted densities than comparative example 1, but were less than comparative example 2.
TABLE 1
Effect example 2
1. Lithium ion battery preparation
The modified graphite materials prepared in examples 1-2 and comparative examples 1-2 were used to prepare lithium-ion button cells as follows.
(1) Preparation of a negative electrode: weighing the modified graphite material, the conductive carbon black SP, the CMC and the SBR according to the mass ratio of 95:1:2:2, uniformly stirring in water to prepare negative electrode slurry, uniformly coating the negative electrode slurry on copper foil by using a coater, putting the coated electrode piece into a vacuum drying oven at the temperature of 110 ℃, performing vacuum drying for 4 hours, and pressing the electrode piece to prepare the negative electrode.
(2) CR-2430 button cell assembly: in a German Braun glove box filled with argon, the electrolyte was 1M LiPF6+ EC: EMC: DMC 1: 1 (volume ratio) and a metallic lithium plate was used as the counter electrode.
2. Electrical Performance testing
Electrochemical performance tests were performed on CR-2430 button cells on an ArbinBT bt2000 model us cell tester.
(1) Discharge capacity and first discharge efficiency
Under the conditions that the charge and discharge voltage range is 0.005V to 1.0V and the charge and discharge rate is 0.1C, the discharge capacity and the discharge efficiency were measured according to the test methods conventionally used in the art, and the test results are shown in table 1. As can be seen from Table 1, the discharge capacity of the lithium ion batteries of examples 1-2 is slightly smaller than that of comparative example 1, but is significantly improved (by 8.2mAh/g at most) compared with that of comparative example 2. The first discharge efficiency of the lithium ion batteries of examples 1 to 2 was lower than that of comparative example 2, but was improved as compared with comparative example 1.
(2) Impedance performance test
The impedance performance test was performed according to the impedance test method conventionally used in the art, and the test results are shown in fig. 2. FIG. 2 is a graph of the AC impedance of examples 1-2 and comparative examples 1-2, the impedance being the diameter of the "semicircle" in the graph: the impedance of example 1 was 7.17 Ω, and the impedance of example 2 was 7.01 Ω; the impedance of comparative example 1 was 8.00 Ω, and the impedance of comparative example 2 was 7.45 Ω. It can be seen that examples 1 to 2 have lower charge transfer resistances than comparative examples 1 to 2.
(3) Rate capability test
According to the conventional method for testing the rate performance in the field, the discharge capacity at 0.2C discharge rate is taken as a reference, and the charge-discharge rate is gradually increased as follows: 0.2C, 0.5C, 1.0C, 2.0C, and 3.0C, and the ratio (retention ratio%) of the discharge capacity of 0.2C to the discharge capacity of 0.2C obtained was plotted to obtain a rate performance graph of examples 1 to 2 and comparative examples 1 to 2, as shown in fig. 3. As can be seen from fig. 3, at 3.0C, the retention ratio of example 1 was 6.81%, the retention ratio of example 2 was 5.84%, the retention ratio of comparative example 1 was 4.68%, and the retention ratio of comparative example 2 was 5.71%. It can be seen that examples 1 to 2 have better discharge rate performance than comparative examples 1 to 2.
In conclusion, the modified graphite material prepared by the method provided by the invention overcomes the problem of rate reduction caused by capacity improvement through one-time coating, and has higher discharge capacity, excellent impedance performance and rate performance.
Claims (10)
1. A preparation method of a modified graphite material comprises the following steps:
s1, preparing graphite particles: sequentially carrying out heat treatment and graphitization on a graphite raw material to obtain graphite particles;
s2, primary coating: fusing the graphite particles and the oily graphene slurry, and performing first carbonization to obtain primary coated graphite particles;
s3, secondary coating: and fusing the primary coated graphite particles with a polyvinylpyrrolidone aqueous solution, and performing second carbonization to obtain the modified graphite material.
2. The method for preparing a modified graphite material according to claim 1, wherein in step S1, the graphite raw material is petroleum coke;
and/or the particle size D50 of the graphite raw material is 8-12 μm, such as 10 μm;
and/or the temperature of the heat treatment is 550-650 ℃;
and/or the time of the heat treatment is 8-22 h;
preferably, the heat treatment is carried out at 630 ℃ for 8 h;
and/or, the heat treatment is carried out under a protective atmosphere; the protective atmosphere is preferably an inert atmosphere or a nitrogen atmosphere;
and/or the heat treatment equipment is a horizontal coating kettle;
and/or the graphitization temperature is 2800-3200 ℃;
and/or the graphitization time is 20-60 h;
preferably, the graphitization is performed for graphitization for 30h at 3000 ℃;
and/or the graphitizing device is an Acheson graphitizing furnace.
3. The method for preparing a modified graphite material according to claim 1, wherein in step S2, the mass ratio of the graphite particles to the oily graphene slurry is 100: (6-20), preferably 100: 9;
and/or the content of graphene in the oily graphene slurry is 5.0 +/-0.2 wt%;
and/or the oily graphene slurry meets the following technical parameters: the water content is less than or equal to 1%, the particle size D50 of the graphene is 7-14 mu m, the viscosity is less than or equal to 3500mPas, the iron content is less than or equal to 10PPm, the cobalt content is less than or equal to 5PPm, and the nickel content is less than or equal to 5 PPm;
and/or the preparation method of the graphene slurry comprises the following steps: heating and stirring graphene and a solvent in a water bath; the temperature of the water bath is preferably between 40 ℃ and 80 ℃, more preferably between 60 ℃ and 70 ℃; the stirring time is preferably 60-90 min; the solvent is white oil, paraffin oil or mineral oil.
4. The method for preparing a modified graphite material according to claim 1, wherein in step S2, the fusion is performed in a fusion machine, preferably at a rotation speed of 250 to 1400 r/min;
and/or the fusion time is 8-60 min;
preferably, the rotating speed of the fusion machine is 280r/min, and the fusion time is 20 min;
and/or the fusion condition is normal temperature and air atmosphere.
5. The method for preparing a modified graphite material according to claim 1, wherein in step S2, the temperature of the first carbonization is 950 to 1350 ℃;
and/or the time of the first carbonization is 0.5-24 h;
preferably, the first carbonization process comprises keeping the temperature at 1150 ℃ for 22 h;
and/or, the first carbonization is carried out under a protective atmosphere, preferably an inert atmosphere or a nitrogen atmosphere;
and/or the first carbonization equipment is a carbonization furnace or an atmosphere protection high-temperature box furnace.
6. The method for preparing a modified graphite material according to claim 1, wherein in step S3, the mass ratio of polyvinylpyrrolidone to water in the polyvinylpyrrolidone aqueous solution is (3-8): 10, preferably (5-7): 10;
and/or the mass ratio of the primary coated graphite particles to the polyvinylpyrrolidone aqueous solution is 100: (10-20), preferably 100: 15;
and/or the preparation method of the polyvinylpyrrolidone aqueous solution comprises the following steps: stirring polyvinylpyrrolidone and water at 80-90 ℃, and cooling; the water is preferably deionized water; the stirring speed is preferably 60 r/min; the stirring time is preferably 1-2 h; the cooling is preferably performed by naturally cooling to room temperature in air.
7. The method for producing a modified graphite material according to claim 1, wherein in step S3, the fusion is performed as described in claim 4;
and/or the temperature of the second carbonization is 550-850 ℃;
and/or the time of the second carbonization is 5-30 h;
preferably, the second carbonization process comprises keeping the temperature at 700 ℃ for 22 h;
and/or, the second carbonization is carried out under a protective atmosphere, preferably an inert atmosphere or a nitrogen atmosphere;
and/or the second carbonization device is an atmosphere protection high-temperature box furnace.
8. A modified graphite material produced by the method for producing a modified graphite material according to any one of claims 1 to 7.
9. A lithium ion battery whose negative electrode material comprises the modified graphite material of claim 8.
10. Use of the modified graphite material according to claim 8 as a negative electrode material in a lithium ion battery.
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| CN114634178A (en) * | 2022-03-15 | 2022-06-17 | 上海杉杉科技有限公司 | Graphite negative electrode material, preparation method thereof, battery and application |
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