CN117558903B - Preparation method of graphene coated lithium iron phosphate - Google Patents
Preparation method of graphene coated lithium iron phosphate Download PDFInfo
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- CN117558903B CN117558903B CN202410037980.6A CN202410037980A CN117558903B CN 117558903 B CN117558903 B CN 117558903B CN 202410037980 A CN202410037980 A CN 202410037980A CN 117558903 B CN117558903 B CN 117558903B
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 121
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 78
- 229910021389 graphene Inorganic materials 0.000 title claims abstract description 46
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 238000000227 grinding Methods 0.000 claims abstract description 37
- 239000000203 mixture Substances 0.000 claims abstract description 33
- 238000000034 method Methods 0.000 claims abstract description 25
- 238000001354 calcination Methods 0.000 claims abstract description 15
- 238000001035 drying Methods 0.000 claims abstract description 15
- 239000002243 precursor Substances 0.000 claims abstract description 12
- 239000000654 additive Substances 0.000 claims abstract description 7
- 230000000996 additive effect Effects 0.000 claims abstract description 7
- 239000010410 layer Substances 0.000 claims description 22
- 239000002245 particle Substances 0.000 claims description 19
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- 239000011259 mixed solution Substances 0.000 claims description 18
- 229910002804 graphite Inorganic materials 0.000 claims description 11
- 239000010439 graphite Substances 0.000 claims description 11
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 11
- KFZMGEQAYNKOFK-UHFFFAOYSA-N Isopropanol Chemical group CC(C)O KFZMGEQAYNKOFK-UHFFFAOYSA-N 0.000 claims description 10
- 238000010438 heat treatment Methods 0.000 claims description 10
- 238000001914 filtration Methods 0.000 claims description 9
- 239000011229 interlayer Substances 0.000 claims description 9
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 238000005507 spraying Methods 0.000 claims description 9
- 238000003756 stirring Methods 0.000 claims description 9
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 9
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 8
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 claims description 8
- LRHPLDYGYMQRHN-UHFFFAOYSA-N N-Butanol Chemical compound CCCCO LRHPLDYGYMQRHN-UHFFFAOYSA-N 0.000 claims description 6
- PHTQWCKDNZKARW-UHFFFAOYSA-N isoamylol Chemical compound CC(C)CCO PHTQWCKDNZKARW-UHFFFAOYSA-N 0.000 claims description 6
- IVKNZCBNXPYYKL-UHFFFAOYSA-N 2-[2-[2-[2-[2-[2-[2-[2-[2-[2-[4-(2,4,4-trimethylpentan-2-yl)phenoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethoxy]ethanol Chemical compound CC(C)(C)CC(C)(C)C1=CC=C(OCCOCCOCCOCCOCCOCCOCCOCCOCCOCCO)C=C1 IVKNZCBNXPYYKL-UHFFFAOYSA-N 0.000 claims description 3
- GSEJCLTVZPLZKY-UHFFFAOYSA-N Triethanolamine Chemical compound OCCN(CCO)CCO GSEJCLTVZPLZKY-UHFFFAOYSA-N 0.000 claims description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 12
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 12
- 239000010405 anode material Substances 0.000 abstract description 2
- 230000008569 process Effects 0.000 abstract description 2
- 238000001291 vacuum drying Methods 0.000 description 10
- 239000000463 material Substances 0.000 description 6
- 239000007774 positive electrode material Substances 0.000 description 5
- 230000000052 comparative effect Effects 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 230000005540 biological transmission Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000001514 detection method Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 238000004146 energy storage Methods 0.000 description 2
- 230000007613 environmental effect Effects 0.000 description 2
- 235000011187 glycerol Nutrition 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012827 research and development Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 238000005229 chemical vapour deposition Methods 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 239000002482 conductive additive Substances 0.000 description 1
- 230000001419 dependent effect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000012286 potassium permanganate Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000001694 spray drying Methods 0.000 description 1
- 239000004094 surface-active agent Substances 0.000 description 1
Classifications
-
- 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 technical field of lithium ion batteries, and particularly relates to a preparation method of graphene coated lithium iron phosphate. The preparation method provided by the invention comprises the following steps: 1) Placing precursor lithium iron phosphate and nano graphite powder into a grinder, adding an additive, and grinding for the first time to obtain a mixture; 2) And drying the mixture, and then calcining and secondary grinding to obtain the graphene coated lithium iron phosphate. According to the method, the graphene-lithium iron phosphate anode material which is stable in thermal performance and capable of improving the capacity and multiplying power performance of the lithium ion battery is prepared by optimizing the process in one step. The method provided by the invention has convenience and effectiveness, and shows a wide practical prospect.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a preparation method of graphene coated lithium iron phosphate.
Background
The rise of new energy automobiles greatly increases the demand for lithium ion batteries. The lithium ion battery has the advantages of high energy density, long cycle life, portability and the like, and is widely applied to various energy storage fields. The performance of the lithium ion battery is greatly dependent on the positive electrode material, and the lithium iron phosphate becomes one of the main positive electrode materials of the lithium ion battery which is commercially used at present due to high theoretical specific capacity, good cycle stability, low price and environmental protection. However, the lithium iron phosphate particles have very limited electrochemical performance due to the defects of low conductivity, easy agglomeration of the particles, high cost of the surfactant, complex solid-liquid separation process and the like. Modification is the most effective strategy for improving electrochemical performance.
Through more than ten years of research and development, the lithium iron phosphate industry in China is gradually complete and cured, and the lithium iron phosphate industry is currently the only country integrating large-scale research and development and commercialization. In recent years, scientific researchers perform functional modification on lithium iron phosphate through means of cladding, doping, particle nanocrystallization, morphology regulation and the like, so that the lithium iron phosphate has good application in the fields of new energy automobile power batteries, starting power supplies, energy storage systems and the like. The charge and discharge performance of the power-assisted lithium iron phosphate material under high power is improved by improving the electronic conductivity and the lithium ion migration rate, which is a main technical approach for developing a quick charge technology; the tap density of the material is improved, so that the high-energy density lithium ion battery positive electrode material is developed, and the material is beneficial to the device application. In addition, the low-temperature performance of the lithium iron phosphate anode material is improved, so that the normal use of the lithium iron phosphate battery in an extreme environment is one of the main development directions of the material in the future.
Among the numerous conductive additives, graphene has received extensive attention from researchers due to its good conductivity, unique molecular structure. However, the traditional graphene has complex preparation process and high production cost, and the steric hindrance barrier under high current density limits the development of the graphene in the field of lithium ion batteries.
CN112694078A discloses a graphene coated lithium iron phosphate composite material and a preparation method thereof, the method comprises: coating graphene oxide and lithium iron phosphate by spray drying or evaporation drying to obtain graphene coated lithium iron phosphate solid, and performing heat treatment on the obtained graphene coated lithium iron phosphate solid to obtain a graphene coated lithium iron phosphate composite material; wherein the ratio of the sheet diameter of the graphene oxide to the D50 of the lithium iron phosphate is 0.05-40. According to the method, although the matching of the graphene oxide sheet diameter and the particle size of the lithium iron phosphate is controlled, the specific surface area of the obtained graphene coated lithium iron phosphate composite material is effectively controlled, and the processing performance of the coated material is greatly improved. But the thermal stability is not satisfactory.
In view of this, the present invention has been made.
Disclosure of Invention
The invention aims to provide a preparation method of graphene coated lithium iron phosphate. According to the method, the graphene-lithium iron phosphate positive electrode material which is stable in thermal performance and capable of improving the capacity and multiplying power performance of the lithium ion battery is prepared by optimizing a process in one step.
In order to achieve the purpose of the invention, the invention adopts the following technical scheme:
the preparation method of the graphene coated lithium iron phosphate comprises the following steps:
1) Placing precursor lithium iron phosphate and nano graphite powder into a grinder, adding an additive, and grinding for the first time to obtain a mixture;
2) Drying the mixture, and then calcining and secondary grinding to obtain graphene coated lithium iron phosphate; the nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 600-1000 ℃ through nitrogen at the speed of 0.5-2 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
Further, in the step 1), the nano graphite powder accounts for 5-30% of the mass of the lithium iron phosphate.
Further, the diameter of the nano graphite powder is 15-25 nanometers, and the number of layers is 10-20.
Further, in the step 1), the addition amount of the additive is 0.1-0.5% of the total mass of the lithium iron phosphate and the nano graphite powder.
Further, the additive is isopropanol, ethanol, glycerol, isoamyl alcohol, butanol, triethanolamine or OP-10.
Further, in step 1), the grinding time of the primary grinding is 3-6 hours.
Further, in the step 2), the drying is performed in a vacuum drying oven at 80-120 ℃ for 3-6 hours.
Further, in the step 2), the calcination is performed under a high-purity nitrogen atmosphere at 500-1000 ℃ for 6-10 hours.
Further, in the step 2), the grinding time of the secondary grinding is 2-4 hours.
Compared with the prior art, the invention has the following advantages:
(1) According to the invention, the nano graphite powder is prepared by using a hydrothermal expansion method, so that the graphite layers are loose, graphene can be better formed in the subsequent preparation process, a common sulfuric acid-potassium permanganate method is avoided, and the environmental protection and cost reduction are facilitated;
(2) The preparation method is simple, and the graphene-lithium iron phosphate composite material can be obtained by adding graphite particles and lithium iron phosphate particles into a grinder without stripping graphene;
(3) The graphene-lithium iron phosphate prepared by the method is not easy to agglomerate due to the fact that the graphene is coated on the surface of the graphene-lithium iron phosphate, and has stable electrochemical performance;
(4) Compared with a carbon material coated by a CVD method, the graphene coated by the graphene-lithium iron phosphate prepared by the method has defects on the surface, so that lithium ions can enter and exit the positive electrode material more easily, the material utilization rate is improved, and the specific energy is higher;
(5) The graphene coated on the surface of the graphene-lithium iron phosphate prepared by the method is stable at high temperature, excellent in heat conduction, easy to dissipate heat and high in safety;
(6) The graphene coated on the surface of the graphene-lithium iron phosphate prepared by the method has excellent conductivity, small internal resistance of the battery and improved performance.
Drawings
FIG. 1 is a transmission electron microscope image of graphene coated lithium iron phosphate particles prepared in example 1, wherein the outer layer is graphene;
fig. 2 is an enlarged view of fig. 1, with graphene uniformly coated, with the scale being the graphene thickness.
Detailed Description
The following are specific embodiments of the present invention, which are described in order to further illustrate the invention, not to limit the invention.
Example 1
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 15 nanometers and the number of layers of 10 layers) into a grinder, adding isopropanol accounting for 0.1 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 3 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 5% of the mass of the lithium iron phosphate;
2) And drying the mixture in a vacuum drying oven at 80 ℃ for 6 hours, calcining the mixture for 6 hours under a high-purity nitrogen atmosphere at 500 ℃, and carrying out secondary grinding for 2 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 800 ℃ through nitrogen at the speed of 1 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
The transmission electron microscope diagrams of the prepared graphene coated lithium iron phosphate particles are shown in fig. 1 and 2.
As can be seen from fig. 1 and 2, graphene is uniformly compounded with lithium iron phosphate particles, the diameters of the lithium iron phosphate particles are 50-80 nanometers, and the thicknesses of the graphene layers are 2.8-4.7 nanometers.
Example 2
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 25 nanometers and the number of layers of 20 layers) into a grinding machine, adding ethanol accounting for 0.5 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 6 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 30% of the mass of the lithium iron phosphate;
2) Drying the mixture in a vacuum drying oven at 85 ℃ for 5.5 hours, calcining the mixture for 10 hours under high-purity nitrogen atmosphere at 1000 ℃ and then carrying out secondary grinding for 4 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 600 ℃ through nitrogen at the speed of 0.5 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
Example 3
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 20 nanometers and the number of layers of 15 layers) into a grinding machine, adding glycerin accounting for 0.3 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 4.5 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 20% of the mass of the lithium iron phosphate;
2) And drying the mixture in a vacuum drying oven at 120 ℃ for 3 hours, calcining the mixture for 8 hours under a high-purity nitrogen atmosphere at 800 ℃, and carrying out secondary grinding for 3 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 1000 ℃ through nitrogen at the speed of 2 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
Example 4
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 18 nanometers and the number of layers of 18 layers) into a grinding machine, adding isoamyl alcohol accounting for 0.2% of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 4 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 18% of the mass of the lithium iron phosphate;
2) And drying the mixture in a vacuum drying oven at 100 ℃ for 4 hours, calcining the mixture for 7.5 hours under a high-purity nitrogen atmosphere at 650 ℃, and then carrying out secondary grinding for 3.5 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 750 ℃ through nitrogen at the speed of 1.5 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
Example 5
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 25 nanometers and the number of layers of 20 layers) into a grinding machine, adding butanol accounting for 0.35 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 5.5 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 8% of the mass of the lithium iron phosphate;
2) And drying the mixture in a vacuum drying oven at 90 ℃ for 5 hours, calcining the mixture for 8.5 hours under the high-purity nitrogen atmosphere at 860 ℃ and then carrying out secondary grinding for 2.5 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 900 ℃ through nitrogen at the speed of 0.8 m/s to obtain graphite particles with loose interlayer structures, namely nano graphite powder.
Example 6
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 22 nanometers and the number of layers of 16 layers) into a grinding machine, adding triethanolamine accounting for 0.25 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 3.5 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 22% of the mass of the lithium iron phosphate;
2) Drying the mixture in a vacuum drying oven at 110 ℃ for 3.5 hours, calcining the mixture for 7 hours under 700 ℃ high-purity nitrogen atmosphere, and carrying out secondary grinding for 3.5 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 850 ℃ through nitrogen at the speed of 1.5 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
Example 7
1) Putting precursor lithium iron phosphate and nano graphite powder (with the diameter of 22 nanometers and the number of layers of 16 layers) into a grinder, adding OP-10 accounting for 0.28 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 3.5 hours at one time to obtain a mixture; wherein the nano graphite powder accounts for 18% of the mass of the lithium iron phosphate;
2) Drying the mixture in a vacuum drying oven at 110 ℃ for 3.5 hours, calcining the mixture for 7.2 hours under 720 ℃ high-purity nitrogen atmosphere, and carrying out secondary grinding for 2.5 hours to obtain the graphene coated lithium iron phosphate.
The nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring for 24 hours to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 680 ℃ through nitrogen at the speed of 1.2 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
Comparative example 1
1) Putting precursor lithium iron phosphate and graphite powder (with the diameter of 1 micron and the number of layers of 800) into a grinder, adding isopropanol accounting for 0.1% of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 3 hours at one time to obtain a mixture; wherein the graphite powder accounts for 5% of the mass of the lithium iron phosphate;
2) And drying the mixture in a vacuum drying oven at 80 ℃ for 6 hours, calcining the mixture for 6 hours under a high-purity nitrogen atmosphere at 500 ℃, and carrying out secondary grinding for 2 hours to obtain the graphene coated lithium iron phosphate.
Comparative example 2
1) Putting precursor lithium iron phosphate and graphite powder (with the diameter of 200 nanometers and the number of layers of 100 layers) into a grinder, adding isopropanol accounting for 0.1 percent of the total mass of the lithium iron phosphate and the graphite powder, and grinding for 3 hours at one time to obtain a mixture; wherein the graphite powder accounts for 22% of the mass of the lithium iron phosphate;
2) And drying the mixture in a vacuum drying oven at 80 ℃ for 6 hours, calcining the mixture for 6 hours under a high-purity nitrogen atmosphere at 500 ℃, and carrying out secondary grinding for 2 hours to obtain the graphene coated lithium iron phosphate.
Test example 1
The test example detects the performance of the graphene coated lithium iron phosphate prepared in the embodiment and the comparative example.
The detection method comprises the following steps: detection was performed according to GB/T18287-2000 standard.
The test results are shown in Table 1 below:
TABLE 1 Performance test results (unit: mAh/g)
From the above test results, it can be seen that the graphene coated lithium iron phosphate prepared by the method of the present invention exhibits higher specific discharge capacity, relatively smooth cycle curve and superior thermal stability compared to the performance of the graphene coated lithium iron phosphate prepared by the method of the comparative example.
Claims (3)
1. The preparation method of the graphene coated lithium iron phosphate is characterized by comprising the following steps of:
1) Placing precursor lithium iron phosphate and nano graphite powder into a grinder, adding an additive, and grinding for the first time to obtain a mixture; the diameter of the nano graphite powder is 15-25 nanometers, and the number of layers is 10-20; the addition amount of the additive is 0.1-0.5% of the total mass of the lithium iron phosphate and the nano graphite powder; the additive is isopropanol, ethanol, glycerol, isoamyl alcohol, butanol, triethanolamine or OP-10; the grinding time of the primary grinding is 3-6 hours;
2) Drying the mixture, and then calcining and secondary grinding to obtain graphene coated lithium iron phosphate; the calcination is calcination for 6-10h under the high-purity nitrogen atmosphere at 500-1000 ℃; the grinding time of the secondary grinding is 2-4 hours; wherein,
the nano graphite powder in the step 1) is prepared by the following method:
1.1 Immersing graphite powder in water, and stirring to obtain a mixed solution;
1.2 Filtering the mixed solution with a plate-and-frame filter, and taking filter residues for later use;
1.3 Spraying the filter residue into a cavity heating furnace at 600-1000 ℃ through nitrogen at the speed of 0.5-2 m/s to obtain graphite particles with loose interlayer structure, namely nano graphite powder.
2. The preparation method according to claim 1, wherein in the step 1), the nano graphite powder accounts for 5-30% of the mass of the lithium iron phosphate.
3. The method according to claim 1, wherein in step 2), the drying is performed in a vacuum oven at 80-120 ℃ for 3-6 hours.
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