CN114162814B - Modification method of graphite - Google Patents
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 57
- 229910002804 graphite Inorganic materials 0.000 title claims abstract description 44
- 239000010439 graphite Substances 0.000 title claims abstract description 44
- 238000002715 modification method Methods 0.000 title abstract description 14
- VSCWAEJMTAWNJL-UHFFFAOYSA-K aluminium trichloride Chemical compound Cl[Al](Cl)Cl VSCWAEJMTAWNJL-UHFFFAOYSA-K 0.000 claims abstract description 60
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims abstract description 39
- 239000011259 mixed solution Substances 0.000 claims abstract description 24
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 20
- 239000003054 catalyst Substances 0.000 claims abstract description 15
- 239000002243 precursor Substances 0.000 claims abstract description 15
- 239000007787 solid Substances 0.000 claims abstract description 15
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 12
- -1 graphite compound Chemical class 0.000 claims abstract description 11
- 238000001027 hydrothermal synthesis Methods 0.000 claims abstract description 10
- 238000002156 mixing Methods 0.000 claims abstract description 10
- 239000007864 aqueous solution Substances 0.000 claims abstract description 7
- 238000010000 carbonizing Methods 0.000 claims abstract description 7
- 239000006184 cosolvent Substances 0.000 claims abstract description 7
- 239000007788 liquid Substances 0.000 claims abstract description 7
- 239000012298 atmosphere Substances 0.000 claims abstract description 3
- 230000001681 protective effect Effects 0.000 claims abstract description 3
- 238000000926 separation method Methods 0.000 claims abstract description 3
- 229910021382 natural graphite Inorganic materials 0.000 claims description 45
- LYCAIKOWRPUZTN-UHFFFAOYSA-N ethylene glycol Natural products OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 11
- 239000002202 Polyethylene glycol Substances 0.000 claims description 8
- 229920001223 polyethylene glycol Polymers 0.000 claims description 8
- 230000000051 modifying effect Effects 0.000 claims description 7
- 239000000243 solution Substances 0.000 claims description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 5
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 5
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 2
- 239000010941 cobalt Substances 0.000 claims description 2
- 125000003827 glycol group Chemical group 0.000 claims description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 230000035484 reaction time Effects 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 37
- 238000002360 preparation method Methods 0.000 abstract description 11
- 238000011049 filling Methods 0.000 abstract description 5
- 230000000052 comparative effect Effects 0.000 description 15
- 238000012360 testing method Methods 0.000 description 12
- 238000005056 compaction Methods 0.000 description 10
- 238000003763 carbonization Methods 0.000 description 9
- 150000001875 compounds Chemical class 0.000 description 9
- 239000007773 negative electrode material Substances 0.000 description 8
- 238000003756 stirring Methods 0.000 description 8
- 230000009286 beneficial effect Effects 0.000 description 7
- 239000008367 deionised water Substances 0.000 description 7
- 229910021641 deionized water Inorganic materials 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 6
- 238000000576 coating method Methods 0.000 description 6
- 238000001914 filtration Methods 0.000 description 6
- 239000002245 particle Substances 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 238000012986 modification Methods 0.000 description 5
- 230000004048 modification Effects 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 239000003607 modifier Substances 0.000 description 4
- 238000011056 performance test Methods 0.000 description 4
- 238000010521 absorption reaction Methods 0.000 description 3
- 229910052786 argon Inorganic materials 0.000 description 3
- 229910021383 artificial graphite Inorganic materials 0.000 description 3
- 239000011230 binding agent Substances 0.000 description 3
- 239000007770 graphite material Substances 0.000 description 3
- 238000010297 mechanical methods and process Methods 0.000 description 3
- 239000000203 mixture Substances 0.000 description 3
- 239000011148 porous material Substances 0.000 description 3
- 239000002994 raw material Substances 0.000 description 3
- 238000001291 vacuum drying Methods 0.000 description 3
- 238000005406 washing Methods 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 229910013870 LiPF 6 Inorganic materials 0.000 description 2
- 239000004698 Polyethylene Substances 0.000 description 2
- 239000004743 Polypropylene Substances 0.000 description 2
- 229910003481 amorphous carbon Inorganic materials 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000000280 densification Methods 0.000 description 2
- 239000012153 distilled water Substances 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229920000573 polyethylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 0.000 description 2
- 238000004321 preservation Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- 229910001228 Li[Ni1/3Co1/3Mn1/3]O2 (NCM 111) Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 239000011294 coal tar pitch Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 239000011267 electrode slurry Substances 0.000 description 1
- 238000009472 formulation Methods 0.000 description 1
- 238000005087 graphitization Methods 0.000 description 1
- 239000001257 hydrogen Substances 0.000 description 1
- 229910052739 hydrogen Inorganic materials 0.000 description 1
- 230000001788 irregular Effects 0.000 description 1
- 238000000462 isostatic pressing Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 239000002086 nanomaterial Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 238000009829 pitch coating Methods 0.000 description 1
- 238000003825 pressing Methods 0.000 description 1
- 238000003672 processing method Methods 0.000 description 1
- 238000004537 pulping Methods 0.000 description 1
- 238000004064 recycling Methods 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
- 238000004154 testing of material Methods 0.000 description 1
- 238000012719 thermal polymerization Methods 0.000 description 1
- 239000011800 void material Substances 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01F—COMPOUNDS OF THE METALS BERYLLIUM, MAGNESIUM, ALUMINIUM, CALCIUM, STRONTIUM, BARIUM, RADIUM, THORIUM, OR OF THE RARE-EARTH METALS
- C01F7/00—Compounds of aluminium
- C01F7/48—Halides, with or without other cations besides aluminium
- C01F7/56—Chlorides
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
-
- 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)
- Organic Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Geology (AREA)
- Life Sciences & Earth Sciences (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Carbon And Carbon Compounds (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention belongs to the field of preparation of graphite, and particularly relates to a modification method of graphite. The modification method of the graphite comprises the following steps: 1) Carrying out hydrothermal reaction on a catalyst, porous carbon and graphite in water at 120-200 ℃, and carrying out solid-liquid separation to obtain a solid precursor; 2) Mixing aluminum chloride, citric acid aqueous solution and cosolvent to obtain a mixed solution; mixing the solid precursor with the mixed solution to obtain an aluminum chloride coated graphite compound; 3) And (3) carbonizing the aluminum chloride coated graphite compound in a protective atmosphere. According to the modification method of graphite, the porous carbon is filled in the gaps of the graphite, and the active points among the gaps are catalyzed by the catalyst, so that the porous carbon is easier to fill between layers, and the filling consistency and the material compactness are improved.
Description
Technical Field
The invention belongs to the field of preparation of graphite, and particularly relates to a modification method of graphite.
Background
With the rapid development of new energy automobile industry, the requirements on the energy density, the cycle performance and the low-temperature rapid charging performance of the lithium ion battery are higher and higher. The negative electrode material is an important component of the lithium ion battery, and the electric performance of the negative electrode material directly influences the realization of the performance of the lithium ion battery.
Graphite is still one of the current stable and widely used negative electrode materials. The graphite can be divided into artificial graphite and natural graphite, and the natural graphite has high specific capacity (more than or equal to 365 mAh/g) and high compaction density (more than or equal to 1.7-1.8g/cm 3), but the material has high expansion rate and poor cycle performance due to poor material density and more pores. One measure for improving the cycle performance of natural graphite is to densify the material.
The Chinese patent application with publication number of CN106629702A discloses a processing method of a high-cycle natural graphite anode material, which is characterized in that after natural graphite raw materials and a modifier are mixed, densification modification of natural graphite is realized through the steps of isostatic pressing treatment, crushing, surface modification, cooling classification and the like. The modification principle is as follows: the modifier enters the material under the action of external pressure to fill the gaps, and after heat treatment, the modifier forms a stable structure of amorphous carbon or artificial graphite, and compared with a high graphitization degree layer structure of natural graphite, the structure has obviously improved cycle performance during high-rate charge and discharge.
The method is characterized in that the modifier is filled into the gaps of the natural graphite by a mechanical method, the operation process of the mechanical method is simpler, the consistency of densification modification is poorer, and the improvement on the compactness and the cycle performance of the material is limited.
Disclosure of Invention
The invention aims to provide a graphite modification method, which has high consistency and remarkably improves the compactness and the cycle performance of materials compared with a mechanical method.
In order to achieve the above object, the technical scheme of the modification method of graphite of the present invention is:
a method for modifying graphite, comprising the steps of:
1) Carrying out hydrothermal reaction on a catalyst, porous carbon and graphite in water at 120-200 ℃, and carrying out solid-liquid separation to obtain a solid precursor; the catalyst is one or two of iron, cobalt and nickel; the mass ratio of the catalyst to the porous carbon is (0.1-0.5): (1-3), the mass ratio of the sum of the mass of the catalyst and the mass of the porous carbon to the mass of the graphite is (1-5): 100;
2) Mixing aluminum chloride, citric acid aqueous solution and cosolvent to obtain a mixed solution; mixing the solid precursor with the mixed solution to obtain an aluminum chloride coated graphite compound; the mass ratio of the aluminum chloride, the citric acid and the cosolvent is 1: (10-30): (10-30), wherein the mass ratio of the sum of the masses of aluminum chloride and citric acid to graphite in the solid precursor is (11-31): 100; the cosolvent is glycol or polyethylene glycol solution;
3) And (3) carbonizing the aluminum chloride coated graphite compound in a protective atmosphere.
According to the modification method of graphite, the porous carbon is filled in the gaps of the graphite, and the active points among the gaps are catalyzed by the catalyst, so that the porous carbon is easier to fill between layers, and the filling consistency and the material compactness are improved. Meanwhile, the composite structure with the aluminum chloride and the amorphous carbon coated on the surface has the characteristics of high temperature resistance and high conductivity, is beneficial to improving the electronic conductivity and the multiplying power performance of the material, and is also beneficial to the safety of the material in the recycling process.
Step 1) is a process for preparing a solid precursor.
The hydrothermal reaction ensures that the raw materials are completely reacted, the specific reaction time can be determined according to the temperature of the hydrothermal reason and the raw material amount, and in the step 1), the time of the hydrothermal reaction is preferably 1-6h. In the hydrothermal reaction, the mass ratio of the catalyst to the porous carbon to the deionized water can be controlled to be (0.1-0.5): 1-3): 100.
The filling modification of graphite is suitable for artificial graphite and natural graphite varieties. Since the natural graphite has a large void, it is preferable that the graphite in step 1) is natural graphite in view of the modifying effect.
Step 2) synthesizing aluminum chloride coated graphite compound. Preferably, in the step 2), the mass fraction of the aqueous solution of citric acid is 1-10%. The mass fraction of the polyethylene glycol solution is 1-10%, wherein the molecular weight of the polyethylene glycol is 6000.
Step 3) is a carbonization process. Preferably, in step 3), the carbonization comprises heat preservation at 250-300 ℃ for 1-3 hours, and then heat preservation at 700-900 ℃ for 1-3 hours. By adopting the carbonization conditions, organic matters such as citric acid, ethylene glycol (or polyethylene glycol) and the like can be fully carbonized, and the coating structure of AlCl 3 can be further stabilized.
Drawings
FIG. 1 is a 500-fold SEM image of a modified natural graphite material obtained in example 1 of the present invention.
Detailed Description
Embodiments of the present invention will be further described with reference to the accompanying drawings. The following examples, porous carbon, having a particle size of 2nm, model: XFP09, available from Nanjing Xianfeng nanomaterials science and technology Co.
1. Specific examples of the modification method of graphite according to the invention
Example 1
The modification method of the graphite of the embodiment comprises the following steps:
1) Preparation of a mixed solution A: 1g of aluminum chloride was added to 400ml of 5wt% aqueous citric acid solution, followed by addition of 20g of ethylene glycol, and stirring was conducted uniformly to obtain a mixed solution A.
2) Preparation of a mixed solution B: to 100ml of deionized water, 0.3g of catalyst iron powder (particle diameter: 200 nm) and 2g of porous carbon were added, followed by stirring to prepare a mixed solution B.
3) Preparation of aluminum chloride coated natural graphite compound: adding 100g of natural graphite into the mixed solution B, carrying out hydrothermal reaction at 150 ℃ for 3 hours, filtering, washing with deionized water, and carrying out vacuum drying at 80 ℃ for 24 hours to obtain a solid precursor; and adding the solid precursor into the mixed solution A, stirring and mixing for 12 hours, and filtering to obtain the aluminum chloride coated natural graphite compound.
4) Carbonizing: transferring the aluminum chloride coated natural graphite compound into a tube furnace, introducing argon, heating to 250 ℃ for carbonization for 3 hours, heating to 800 ℃ for carbonization for 2 hours, and naturally cooling to room temperature.
Example 2
The modification method of the graphite of the embodiment comprises the following steps:
1) Preparation of a mixed solution A: 1g of aluminum chloride was added to 1000ml of a 1wt% aqueous solution of citric acid, followed by 10ml of a polyethylene glycol solution (the polyethylene glycol solution has a mass fraction of 5% and the polyethylene glycol has a molecular weight of 6000) and stirred uniformly to obtain a mixed solution A.
2) Preparation of a mixed solution B: to 100ml of deionized water, 0.1g of catalyst nickel powder (particle diameter 100 nm) and 1g of porous carbon were added, followed by stirring to prepare a mixed solution B.
3) Preparation of aluminum chloride coated natural graphite compound: adding 100g of natural graphite into the mixed solution B, performing hydrothermal reaction at 120 ℃ for 6 hours, filtering, washing with deionized water, and performing vacuum drying at 80 ℃ for 24 hours to obtain a solid precursor; and adding the solid precursor into the mixed solution A, stirring and mixing for 12 hours, and filtering to obtain the aluminum chloride coated natural graphite compound.
4) Carbonizing: transferring the aluminum chloride coated natural graphite compound into a tube furnace, introducing argon, heating to 300 ℃ for carbonization for 1h, heating to 700 ℃ for carbonization for 3h, and naturally cooling to room temperature.
Example 3
The modification method of the graphite of the embodiment comprises the following steps:
1) Preparation of a mixed solution A: 1g of aluminum chloride was added to 300ml of a 10wt% aqueous solution of citric acid, followed by addition of 30ml of ethylene glycol, and stirred well to obtain a mixed solution A.
2) Preparation of a mixed solution B: to 100ml of deionized water, 0.5g of catalyst cobalt powder (particle diameter 500 nm) and 3g of porous carbon were added, followed by stirring to prepare a mixed solution B.
3) Preparation of aluminum chloride coated natural graphite compound: adding 100g of natural graphite into the mixed solution B, carrying out hydrothermal reaction at 200 ℃ for 1h, filtering, washing with deionized water, and carrying out vacuum drying at 80 ℃ for 24h to obtain a solid precursor; and adding the solid precursor into the mixed solution A, stirring and mixing for 12 hours, and filtering to obtain the aluminum chloride coated natural graphite compound.
4) Carbonizing: transferring the aluminum chloride coated natural graphite compound into a tube furnace, introducing argon, heating to 300 ℃ for carbonization for 1h, heating to 700 ℃ for carbonization for 3h, and naturally cooling to room temperature.
2. Comparative example
The graphite modification method of the comparative example comprises the steps of mixing 100g of natural graphite with 50g of coal tar pitch coating material and 500ml of N-methyl pyrrolidone solvent at the temperature of 200 ℃, vacuumizing to remove the solvent, and coating the natural graphite in the coating material; and then the materials are placed under the protection of nitrogen at 400 ℃ for thermal polymerization for 3 hours, and the obtained product is carbonized for 12 hours under the condition of 900 ℃.
3. Experimental example
Experimental example 1 physicochemical Property test
1.1SEM test
SEM test was performed on the natural graphite modified material prepared in example 1, and the result is shown in fig. 1.
As can be seen from the figure, the natural graphite modified material is in an irregular particle shape, the surface is compact and smooth, and the average particle size is 8-12 mu m.
1.2 Compaction Density and tap Density test
The natural graphite modified materials of examples 1 to 3 and comparative examples were subjected to the compaction density and tap density test, and the results are shown in table 1.
Compaction density testing: placing the powder material into a compaction density instrument, adopting 2T pressure for pressing, maintaining the pressure for 10s, calculating the descending height of the powder, and then calculating the powder compaction density of the material.
Tap density test: reference is made to the specification of GB/T24533-2009 lithium ion battery graphite negative electrode material.
TABLE 1 compaction and tap Density testing of materials
| Project | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Powder compaction Density (g/cm 3) | 1.79 | 1.77 | 1.75 | 1.52 |
| Powder tap Density (g/cm 3) | 1.19 | 1.18 | 1.17 | 0.98 |
As can be seen from the results of table 1, the compaction density and tap density of the modified natural graphite material of the examples are significantly higher than those of the comparative examples, which shows that the method of the examples is used to fill porous carbon in the pores of natural graphite and coat aluminum chloride with high electrical rate and density on the surface, which is beneficial to improving the compaction density and tap density of the powder material.
Experimental example 2 button cell test
The natural graphite modified materials of examples 1-3 and comparative examples were assembled into button cells.
The button cell comprises the following steps: and adding a binder, a conductive agent and a solvent into the negative electrode material, stirring and pulping, coating the mixture on a copper foil, and drying and rolling the mixture to obtain the negative electrode plate. The binder used was LA132 binder, the conductive agent was SP, the negative electrode materials were the natural graphite modified materials of examples 1 to 3 and comparative examples, respectively, and the solvent was secondary distilled water. The mass ratio of each component is as follows: negative electrode material: SP: LA132: secondary distilled water = 95g:1g:4g:220mL; the electrolyte is LiPF 6/EC+DEC(LiPF6 with the concentration of 1.2mol/L and the volume ratio of EC to DEC of 1:1, the lithium metal sheet is a counter electrode, and the diaphragm adopts a Polyethylene (PE), polypropylene (PP) or polyethylene propylene (PEP) composite film. The assembly of the coin cell was performed in a hydrogen filled glove box.
The electrochemical performance test is carried out on a Wuhan blue electric CT2001A type battery tester, the charge-discharge voltage ranges from 0.005V to 2.0V, and the charge-discharge multiplying power is 0.1C. And simultaneously taking the negative plate, and testing the liquid absorption and retention capacity of the plate. The test results are shown in Table 2.
Table2 comparative performance of button cells and pole pieces using the natural graphite modified materials of examples and comparative examples
| Project | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| First discharge capacity (mAh/g) | 362.3 | 361.4 | 360.5 | 354.4 |
| First time efficiency (%) | 95.1 | 94.8 | 94.7 | 93.2 |
| Liquid absorbing ability (mL/min) | 9.8 | 9.3 | 8.8 | 5.4 |
As can be seen from the results in Table 2, the first discharge capacity and the first charge-discharge efficiency of the modified natural graphite materials of examples 1-3 are significantly higher than those of the comparative examples, which indicates that the aluminum chloride material with high surface coating conductivity and high gram capacity is beneficial to improving the gram capacity exertion and the first efficiency of the material. Meanwhile, the natural graphite is filled and modified by porous carbon, so that the liquid absorption capacity of the material is improved, and the material is beneficial to improving the electrical property of the material.
Experimental example 3 Soft packet Battery test
The negative electrode sheets were prepared with the natural graphite modified materials of examples 1 to 3 and comparative examples as negative electrode materials, referring to the formulation of the negative electrode slurry for button cells. Ternary material (LiNi 1/3Co1/3Mn1/3O2) is used as an anode, liPF 6 solution (solvent is EC+DEC, volume ratio is 1:1, concentration of LiPF 6 is 1.3 mol/L) is used as electrolyte, celegard2400 is used as a diaphragm, a 5Ah soft package battery is prepared, and then cycle performance and rate capability of the soft package battery are tested.
And (3) testing the cycle performance: the charge-discharge current is 3C/3C, the voltage range is 2.8-4.3V, the cycle times are 500 and 1000, and the full-charge expansion of the pole piece after 500 cycles is tested.
And (3) multiplying power performance test: charging multiplying power 1C/2C/3C/5C, discharging multiplying power 1C; voltage range: 2.8-4.3V.
Table 3 cycle performance test of flexible package batteries using natural graphite modified materials of examples and comparative examples
As can be seen from the results in table 3, the cycle performance of the soft-pack battery using the natural graphite modified material of the example is superior to that of the comparative example, which shows that filling porous carbon in the pores of the natural graphite can improve the structural stability and the liquid absorption and retention capability of the material during charge and discharge, and is beneficial to improving the cycle performance of the negative electrode. Meanwhile, the natural graphite modified material of the embodiment has better structural stability and smaller full-charge expansion, and is also beneficial to improving the cycle performance of the battery.
Table 4 rate performance test of flexible pouch batteries using natural graphite modified materials of examples and comparative examples
As can be seen from the results of table 4, the soft-pack battery using the natural graphite modified material of the example has a higher constant current ratio, because the porous carbon filling and aluminum chloride coating of the natural graphite can improve the structural stability and the conductivity of the material, and thus can improve the rate capability of the material.
Claims (5)
1. A method for modifying graphite, comprising the steps of:
1) Carrying out hydrothermal reaction on a catalyst, porous carbon and graphite in water at 120-200 ℃, and carrying out solid-liquid separation to obtain a solid precursor; the catalyst is one or two of iron, cobalt and nickel; the mass ratio of the catalyst to the porous carbon is (0.1-0.5): (1-3), the mass ratio of the sum of the mass of the catalyst and the mass of the porous carbon to the mass of the graphite is (1-5): 100;
2) Mixing aluminum chloride, citric acid aqueous solution and cosolvent to obtain a mixed solution; mixing the solid precursor with the mixed solution to obtain an aluminum chloride coated graphite compound; the mass ratio of the aluminum chloride, the citric acid and the cosolvent is 1: (10-30): (10-30), wherein the mass ratio of the sum of the masses of aluminum chloride and citric acid to graphite in the solid precursor is (11-31): 100; the cosolvent is glycol or polyethylene glycol solution;
3) And (3) carbonizing the aluminum chloride coated graphite compound in a protective atmosphere.
2. The method for modifying graphite as claimed in claim 1, wherein in the step 1), the hydrothermal reaction time is 1 to 6 hours.
3. The method for modifying graphite according to claim 2, wherein in step 1), the graphite is natural graphite.
4. The method for modifying graphite as claimed in claim 1, wherein in the step 2), the mass fraction of the aqueous solution of citric acid is 1 to 10%.
5. The method of modifying graphite as claimed in any one of claims 1 to 4, wherein in step 3), the carbonizing comprises first maintaining the temperature at 250 to 300 ℃ for 1 to 3 hours, and then raising the temperature to 700 to 900 ℃ for 1 to 3 hours.
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