CN114162814A - 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 claims abstract description 15
- 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 12
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- 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 9
- 238000010000 carbonizing Methods 0.000 claims abstract description 8
- 239000006184 cosolvent Substances 0.000 claims abstract description 7
- 239000007864 aqueous solution Substances 0.000 claims abstract description 6
- 239000012298 atmosphere Substances 0.000 claims abstract description 3
- 230000001681 protective effect Effects 0.000 claims abstract description 3
- 229910021382 natural graphite Inorganic materials 0.000 claims description 45
- 238000000034 method Methods 0.000 claims description 13
- LYCAIKOWRPUZTN-UHFFFAOYSA-N ethylene glycol Natural products OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 10
- 239000002202 Polyethylene glycol Substances 0.000 claims description 8
- 238000003763 carbonization Methods 0.000 claims description 8
- 229920001223 polyethylene glycol Polymers 0.000 claims description 8
- 239000000243 solution Substances 0.000 claims description 8
- 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
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims description 3
- 230000035484 reaction time Effects 0.000 claims description 3
- 125000003827 glycol group Chemical group 0.000 claims description 2
- 229910052742 iron Inorganic materials 0.000 claims description 2
- 229910052759 nickel Inorganic materials 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 39
- 238000002360 preparation method Methods 0.000 abstract description 9
- 238000011049 filling Methods 0.000 abstract description 6
- 230000000052 comparative effect Effects 0.000 description 14
- 238000012360 testing method Methods 0.000 description 14
- 150000001875 compounds Chemical class 0.000 description 9
- 238000003756 stirring Methods 0.000 description 9
- 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
- 239000000843 powder Substances 0.000 description 7
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 6
- 238000001914 filtration Methods 0.000 description 6
- 238000012986 modification Methods 0.000 description 6
- 230000004048 modification Effects 0.000 description 6
- 239000007773 negative electrode material Substances 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 238000005056 compaction Methods 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 239000002904 solvent Substances 0.000 description 5
- 238000001816 cooling Methods 0.000 description 4
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- 229910001290 LiPF6 Inorganic materials 0.000 description 3
- 238000010521 absorption reaction Methods 0.000 description 3
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- 239000011230 binding agent Substances 0.000 description 3
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- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 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
- 239000010405 anode material Substances 0.000 description 2
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- 229920000573 polyethylene Polymers 0.000 description 2
- 229920001155 polypropylene Polymers 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
- 229910013716 LiNi Inorganic materials 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 230000009471 action Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
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- 239000011294 coal tar pitch Substances 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 239000012153 distilled water Substances 0.000 description 1
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- 239000011267 electrode slurry Substances 0.000 description 1
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- 238000000462 isostatic pressing Methods 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 239000012528 membrane Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
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- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 239000000126 substance Substances 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
Images
Classifications
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- 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
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 the catalyst, the porous carbon and the graphite in water at the temperature of 120-; 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 carbonizing the aluminum chloride coated graphite compound under a protective atmosphere. According to the modification method of the graphite, the porous carbon is filled in the graphite gaps, and the catalyst is used for catalyzing active points among the gaps, so that the porous carbon is more easily filled among the layers, and the filling consistency and the material density 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 the new energy automobile industry, the requirements on the energy density, the cycle performance and the low-temperature quick-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 electrical performance of the negative electrode material directly influences the realization of the performance of the lithium ion battery.
Graphite is still one of the anode materials which have stable performance and are widely used at present. The graphite can be divided into artificial graphite and natural graphite, and the natural graphite has high specific capacity (more than or equal to 365mAh/g) and high compaction density (more than or equal to 1.7-1.8 g/cm)3) However, the material has poor compactness and more pores, so that the material has high expansion rate and poor cycle performance. One of the measures for improving the cycle performance of the natural graphite is to perform densification treatment on the material.
The Chinese patent application with application publication number CN106629702A discloses a processing method of a high-cycle natural graphite negative electrode material, which is to mix a natural graphite raw material and a modifier, and realize densification modification of natural graphite 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 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 the advantage that the cycle performance is obviously improved during high-rate charge and discharge.
The method is characterized in that the modifier is filled in gaps of the natural graphite by adopting a mechanical method, the operation process of the mechanical method is simpler, the consistency of densification modification is poorer, and the improvement on the material density and the cycle performance is limited.
Disclosure of Invention
The invention aims to provide a graphite modification method which has high consistency and obviously improves the compactness and the cycle performance of materials compared with a mechanical method.
In order to achieve the purpose, the technical scheme of the modification method of the graphite is as follows:
a modification method of graphite comprises the following steps:
1) carrying out hydrothermal reaction on the catalyst, the porous carbon and the graphite in water at the temperature of 120-; 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 porous carbon to the mass of the graphite is (1-5): 100, respectively;
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 to the citric acid to the cosolvent is 1: (10-30): (10-30), wherein the mass ratio of the sum of the mass of the aluminum chloride and the mass of the citric acid to the mass of the graphite in the solid precursor is (11-31): 100, respectively; the cosolvent is glycol or polyethylene glycol solution;
3) and carbonizing the aluminum chloride coated graphite compound under a protective atmosphere.
According to the modification method of the graphite, the porous carbon is filled in the graphite gaps, and the catalyst is used for catalyzing active points among the gaps, so that the porous carbon is more easily filled among the layers, and the filling consistency and the material density are improved. Meanwhile, the composite structure with the surface coated with the aluminum chloride and the amorphous carbon has the characteristics of high temperature resistance and high conductivity, is favorable for improving the electronic conductivity and the rate capability of the material, and is also favorable for the safety of the material in the circulating process.
Step 1) is a preparation process of a solid precursor.
The hydrothermal reaction is carried out for ensuring the completion of the raw material reaction, the specific reaction time can be determined according to the hydrothermal reason temperature and the raw material amount, and preferably, in the step 1), the hydrothermal reaction time is 1-6 h. During the hydrothermal reaction, the mass ratio of the catalyst, the porous carbon and the deionized water can be controlled to be (0.1-0.5): (1-3): 100.
The filling modification of the graphite is suitable for artificial graphite and natural graphite. Since natural graphite has large voids, it is preferable that the graphite in step 1) is natural graphite in view of modification effect.
And 2) synthesizing an aluminum chloride coated graphite compound. Preferably, in the step 2), the mass fraction of the citric acid aqueous solution 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 the step 3), the carbonization comprises firstly preserving heat at 300 ℃ for 1-3h, and then raising the temperature to 900 ℃ for 1-3 h. By adopting the carbonization conditions, organic matters such as citric acid, glycol (or polyethylene glycol) and the like can be fully carbonized, and AlCl is also ensured3The coating structure of (a) is further stabilized.
Drawings
FIG. 1 is a SEM image of 500 times of the natural graphite modified material obtained in example 1 of the present invention.
Detailed Description
The following further describes embodiments of the present invention with reference to the drawings. In the following examples, the particle size of the porous carbon was 2nm, type: XFP09, available from Nanjing Xiancheng nanomaterial science and technology Co.
First, a specific example of the method for modifying graphite of the present invention
Example 1
The modification method of graphite of the embodiment comprises the following steps:
1) preparation of mixed solution A: 1g of aluminum chloride was added to 400ml of a 5 wt% aqueous citric acid solution, and then 20g of ethylene glycol was added thereto and stirred uniformly to obtain a mixed solution A.
2) Preparation of mixed solution B: to 100ml of deionized water, 0.3g of catalyst iron powder (particle size: 200nm) and 2g of porous carbon were added, followed by stirring to prepare a mixed solution B.
3) Preparing an aluminum chloride coated natural graphite compound: adding 100g of natural graphite into the mixed solution B, carrying out hydrothermal reaction for 3h at 150 ℃, filtering, washing with deionized water, and carrying out vacuum drying for 24h at 80 ℃ 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 tubular furnace, introducing argon, heating to 250 ℃, carbonizing for 3 hours, heating to 800 ℃, carbonizing for 2 hours, and naturally cooling to room temperature.
Example 2
The modification method of graphite of the embodiment comprises the following steps:
1) preparation of mixed solution A: adding 1g of aluminum chloride into 1000ml of 1 wt% citric acid aqueous solution, adding 10ml of polyethylene glycol solution (the mass fraction of the polyethylene glycol solution is 5%, and the molecular weight of the polyethylene glycol is 6000), and uniformly stirring to obtain a mixed solution A.
2) Preparation of mixed solution B: 0.1g of nickel powder (particle size: 100nm) as a catalyst and 1g of porous carbon were added to 100ml of deionized water, followed by stirring to prepare a mixed solution B.
3) Preparing an aluminum chloride coated natural graphite compound: adding 100g of natural graphite into the mixed solution B, carrying out hydrothermal reaction for 6h at 120 ℃, filtering, washing with deionized water, and carrying out vacuum drying for 24h at 80 ℃ 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 tubular furnace, introducing argon, heating to 300 ℃ for carbonization for 1h, heating to 700 ℃ for carbonization for 3h, and then naturally cooling to room temperature.
Example 3
The modification method of graphite of the embodiment comprises the following steps:
1) preparation of mixed solution A: 1g of aluminum chloride was added to 300ml of a 10 wt% aqueous solution of citric acid, and then 30ml of ethylene glycol was added thereto, followed by stirring to obtain a mixed solution A.
2) Preparation of mixed solution B: to 100ml of deionized water, 0.5g of cobalt catalyst powder (particle size 500nm) and 3g of porous carbon were added, followed by stirring to prepare a mixed solution B.
3) Preparing an aluminum chloride coated natural graphite compound: adding 100g of natural graphite into the mixed solution B, carrying out hydrothermal reaction for 1h at 200 ℃, 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 tubular furnace, introducing argon, heating to 300 ℃ for carbonization for 1h, heating to 700 ℃ for carbonization for 3h, and then naturally cooling to room temperature.
Second, comparative example
The graphite modification method of the comparative example is to mix 100g of natural graphite, 50g of coal tar pitch coating material and 500ml of N-methyl pyrrolidone solvent at the temperature of 200 ℃, vacuumize to remove the solvent, and coat the natural graphite in the coating material; then the materials are put into nitrogen protection gas at the temperature of 400 ℃ for thermal polymerization for 3h, and the obtained product is carbonized for 12h at the temperature of 900 ℃.
Third, Experimental example
Experimental example 1 test of physical and chemical Properties
1.1SEM test
The SEM test of the natural graphite modified material obtained in example 1 was performed, and the result is shown in fig. 1.
As can be seen from the figure, the natural graphite modified material is irregular granular, the surface is compact and smooth, and the average grain diameter is 8-12 μm.
1.2 compacted and tap Density test
The natural graphite modified materials of examples 1 to 3 and comparative example were subjected to the compaction density and tap density tests, and the results are shown in table 1.
Testing of compacted density: and putting the powder material into a compaction density instrument, pressing by adopting the pressure of 2T, maintaining the pressure for 10s, calculating the powder falling height, and then calculating the powder compaction density of the material.
And (3) testing tap density: the method is carried out according to the stipulations of GB/T2433and 2009 graphite cathode materials of lithium ion batteries.
Table 1 compaction and tap Density testing of materials
| Item | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| Powder compacted density (g/cm)3) | 1.79 | 1.77 | 1.75 | 1.52 |
| Tap density (g/cm) of powder3) | 1.19 | 1.18 | 1.17 | 0.98 |
As can be seen from the results in table 1, the compacted density and the tap density of the natural graphite modified materials of the examples are significantly higher than those of the comparative examples, which shows that the method of the examples is advantageous for increasing the compacted density and the tap density of the powder material by filling the porous carbon in the pores of the natural graphite and coating the surface with aluminum chloride having a high electrical conductivity and density.
Experimental example 2 button cell test
The natural graphite modified materials of examples 1-3 and comparative example were assembled into button cells.
The button cell battery method 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 copper foil, and drying and rolling 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 1-3 and comparative example, respectively, and the solvent was redistilled water. The mass ratio of each component is as follows: and (3) anode material: SP: LA 132: 95g of secondary distilled water: 1 g: 4 g: 220mL; the electrolyte is LiPF6/EC+DEC(LiPF6The concentration of the lithium ion battery is 1.2mol/L, the volume ratio of EC to DEC is 1:1), the metal lithium sheet is used as a counter electrode, and the diaphragm is a Polyethylene (PE), polypropylene (PP) or polyethylene propylene (PEP) composite membrane. The assembly of the button cells was carried out in a hydrogen-filled glove box.
The electrochemical performance test is carried out on a Wuhan blue electricity CT2001A type battery tester, the charge-discharge voltage range is 0.005V-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 negative plate. The test results are shown in table 2.
TABLE 2 comparison of performance of button cells and electrode sheets using the natural graphite modified materials of the examples and comparative examples
| Item | Example 1 | Example 2 | Example 3 | Comparative example 1 |
| First discharge capacity (mAh/g) | 362.3 | 361.4 | 360.5 | 354.4 |
| First efficiency (%) | 95.1 | 94.8 | 94.7 | 93.2 |
| Liquid suction capacity (mL/min) | 9.8 | 9.3 | 8.8 | 5.4 |
From the results in table 2, it can be seen that the first discharge capacity and the first charge-discharge efficiency of the natural graphite modified materials of examples 1-3 are significantly higher than those of the comparative examples, indicating that the aluminum chloride material with high surface conductivity and high gram capacity is beneficial to improving gram capacity performance and first efficiency of the materials. Meanwhile, the natural graphite is modified by filling porous carbon, so that the liquid absorption capacity of the material is improved, and the improvement of the electrical property of the material is facilitated.
Experimental example 3 pouch cell test
The natural graphite modified materials of examples 1-3 and comparative example were used as negative electrode materials, and negative electrode sheets were prepared with reference to the formulation of button cell negative electrode slurry. With ternary materials (LiNi)1/3Co1/3Mn1/3O2) As the positive electrode, LiPF6Solution (solvent EC + DEC, volume ratio 1:1, LiPF)6Concentration of 1.3mol/L) is used as electrolyte, celegard2400 is used as a diaphragm, a 5Ah soft package battery is prepared, and then the cycle performance and the rate performance of the soft package battery are tested.
And (3) testing the cycle performance: the charging and discharging current is 3C/3C, the voltage range is 2.8-4.3V, the cycle times are 500 and 1000, and the full electric expansion of the pole piece after 500 cycles is tested.
And (3) rate performance test: the charging multiplying power is 1C/2C/3C/5C, and the discharging multiplying power is 1C; voltage range: 2.8-4.3V.
Table 3 cycle performance testing of pouch cells using the natural graphite modified materials of each example and comparative example
From the results in table 3, it can be seen that the cycle performance of the pouch battery using the natural graphite modified material of the example is superior to that of the comparative example, and it is demonstrated that the porous carbon is filled in the pores of the natural graphite, so that the structural stability and the liquid absorption and retention capacity of the material in the charging and discharging processes can be improved, and the improvement of the cycle performance of the negative electrode is facilitated. Meanwhile, the natural graphite modified material of the embodiment has better structural stability and smaller full-electricity expansion, and is also favorable for improving the cycle performance of the battery.
Table 4 rate performance testing of pouch cells using the natural graphite modified materials of each example and comparative example
As can be seen from the results in table 4, the pouch battery using the natural graphite modified material of the embodiment has a higher constant current ratio, because the porous carbon filling and the aluminum chloride coating of the natural graphite can improve the structural stability and the conductivity of the material, thereby improving the rate capability of the material.
Claims (5)
1. A modification method of graphite is characterized by comprising the following steps:
1) carrying out hydrothermal reaction on the catalyst, the porous carbon and the graphite in water at the temperature of 120-; 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 porous carbon to the mass of the graphite is (1-5): 100, respectively;
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 to the citric acid to the cosolvent is 1: (10-30): (10-30), wherein the mass ratio of the sum of the mass of the aluminum chloride and the mass of the citric acid to the mass of the graphite in the solid precursor is (11-31): 100, respectively; the cosolvent is glycol or polyethylene glycol solution;
3) and carbonizing the aluminum chloride coated graphite compound under a protective atmosphere.
2. The method for modifying graphite according to claim 1, wherein the hydrothermal reaction time in step 1) 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 according to claim 1, wherein the mass fraction of the aqueous citric acid solution in step 2) is 1 to 10%.
5. The method for modifying graphite as claimed in any one of claims 1 to 4, wherein the carbonization step 3) comprises first maintaining the temperature at 300 ℃ for 1 to 3 hours and then raising the temperature to 900 ℃ for 1 to 3 hours.
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