CN113571697A - Nanoscale lithium iron phosphate cathode material capable of improving low-temperature performance in screening and grading manner and preparation method thereof - Google Patents
Nanoscale lithium iron phosphate cathode material capable of improving low-temperature performance in screening and grading manner and preparation method thereof Download PDFInfo
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- CN113571697A CN113571697A CN202110803973.9A CN202110803973A CN113571697A CN 113571697 A CN113571697 A CN 113571697A CN 202110803973 A CN202110803973 A CN 202110803973A CN 113571697 A CN113571697 A CN 113571697A
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- iron phosphate
- lithium iron
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- 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 60
- 238000012216 screening Methods 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- 239000010406 cathode material Substances 0.000 title claims description 15
- 239000000463 material Substances 0.000 claims abstract description 58
- 239000002245 particle Substances 0.000 claims abstract description 37
- 229910052726 zirconium Inorganic materials 0.000 claims abstract description 34
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 claims abstract description 32
- 238000000227 grinding Methods 0.000 claims abstract description 32
- 238000001694 spray drying Methods 0.000 claims abstract description 13
- 239000010405 anode material Substances 0.000 claims abstract description 12
- 238000000034 method Methods 0.000 claims abstract description 11
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 239000002002 slurry Substances 0.000 claims description 22
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 17
- 239000007787 solid Substances 0.000 claims description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 15
- 229910052744 lithium Inorganic materials 0.000 claims description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 14
- 239000002243 precursor Substances 0.000 claims description 14
- 229910052799 carbon Inorganic materials 0.000 claims description 13
- 238000010902 jet-milling Methods 0.000 claims description 13
- 239000007774 positive electrode material Substances 0.000 claims description 13
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 12
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 12
- 239000005955 Ferric phosphate Substances 0.000 claims description 7
- 229940032958 ferric phosphate Drugs 0.000 claims description 7
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 5
- 229930006000 Sucrose Natural products 0.000 claims description 5
- 239000006185 dispersion Substances 0.000 claims description 5
- 239000005720 sucrose Substances 0.000 claims description 5
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- 229910052782 aluminium Inorganic materials 0.000 claims description 4
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 4
- 239000000843 powder Substances 0.000 claims description 4
- -1 dihydrate ferric phosphate Chemical class 0.000 claims description 3
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 claims description 2
- 239000002202 Polyethylene glycol Substances 0.000 claims description 2
- 239000004372 Polyvinyl alcohol Substances 0.000 claims description 2
- 229920002472 Starch Polymers 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 2
- 229910052804 chromium Inorganic materials 0.000 claims description 2
- 239000008103 glucose Substances 0.000 claims description 2
- 239000011261 inert gas Substances 0.000 claims description 2
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 2
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 2
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 2
- 229910052749 magnesium Inorganic materials 0.000 claims description 2
- 230000014759 maintenance of location Effects 0.000 claims description 2
- 229910052748 manganese Inorganic materials 0.000 claims description 2
- 229910052754 neon Inorganic materials 0.000 claims description 2
- GKAOGPIIYCISHV-UHFFFAOYSA-N neon atom Chemical compound [Ne] GKAOGPIIYCISHV-UHFFFAOYSA-N 0.000 claims description 2
- 229910052758 niobium Inorganic materials 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- 229920001223 polyethylene glycol Polymers 0.000 claims description 2
- 229920002451 polyvinyl alcohol Polymers 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims description 2
- 239000008107 starch Substances 0.000 claims description 2
- 235000019698 starch Nutrition 0.000 claims description 2
- 229910052719 titanium Inorganic materials 0.000 claims description 2
- 229910052720 vanadium Inorganic materials 0.000 claims description 2
- 229910052725 zinc Inorganic materials 0.000 claims description 2
- 239000004576 sand Substances 0.000 abstract description 28
- 238000005245 sintering Methods 0.000 abstract description 21
- 238000004519 manufacturing process Methods 0.000 abstract description 9
- 230000005540 biological transmission Effects 0.000 abstract description 4
- 150000002500 ions Chemical class 0.000 abstract description 3
- 239000011164 primary particle Substances 0.000 abstract description 3
- 238000009792 diffusion process Methods 0.000 abstract description 2
- 238000012545 processing Methods 0.000 abstract description 2
- 238000001816 cooling Methods 0.000 description 10
- 239000008367 deionised water Substances 0.000 description 10
- 229910021641 deionized water Inorganic materials 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 7
- 238000010438 heat treatment Methods 0.000 description 7
- 239000000203 mixture Substances 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 239000011267 electrode slurry Substances 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 239000004480 active ingredient Substances 0.000 description 3
- 238000010586 diagram Methods 0.000 description 3
- 238000007599 discharging Methods 0.000 description 3
- 238000001035 drying Methods 0.000 description 3
- 238000003801 milling Methods 0.000 description 3
- 238000005507 spraying Methods 0.000 description 3
- 239000002033 PVDF binder Substances 0.000 description 2
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 2
- 239000003153 chemical reaction reagent Substances 0.000 description 2
- 239000006258 conductive agent Substances 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 239000008187 granular material Substances 0.000 description 2
- 238000007709 nanocrystallization Methods 0.000 description 2
- 229910021382 natural graphite Inorganic materials 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000004804 winding Methods 0.000 description 2
- RYGMFSIKBFXOCR-UHFFFAOYSA-N Copper Chemical compound [Cu] RYGMFSIKBFXOCR-UHFFFAOYSA-N 0.000 description 1
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 229910001290 LiPF6 Inorganic materials 0.000 description 1
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 description 1
- 239000004698 Polyethylene Substances 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 150000001768 cations Chemical class 0.000 description 1
- 238000007600 charging Methods 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010280 constant potential charging Methods 0.000 description 1
- 238000010277 constant-current charging Methods 0.000 description 1
- 238000010281 constant-current constant-voltage charging Methods 0.000 description 1
- 238000007796 conventional method Methods 0.000 description 1
- 239000011889 copper foil Substances 0.000 description 1
- 125000004122 cyclic group Chemical group 0.000 description 1
- 238000005265 energy consumption Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000011255 nonaqueous electrolyte Substances 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 229920000573 polyethylene Polymers 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
Images
Classifications
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- 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
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B02—CRUSHING, PULVERISING, OR DISINTEGRATING; PREPARATORY TREATMENT OF GRAIN FOR MILLING
- B02C—CRUSHING, PULVERISING, OR DISINTEGRATING IN GENERAL; MILLING GRAIN
- B02C21/00—Disintegrating plant with or without drying of the material
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
- H01M4/139—Processes of manufacture
- H01M4/1391—Processes of manufacture of electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/51—Particles with a specific particle size distribution
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
-
- 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 provides a nanoscale lithium iron phosphate anode material capable of improving low-temperature performance by screening and grading and a preparation method thereof, and the preparation method comprises the following steps: (1) mixing materials; (2) dispersing; (3) coarse grinding; (4) carrying out middle grinding; (5) fine grinding; (6) spray drying; (7) sintering in inert atmosphere; (8) airflow crushing; (9) and (4) screening and grading. According to the invention, through optimizing and matching the diameter of the zirconium ball in the sand grinding process, the particles can be quickly ground to be small, the sand grinding time is greatly shortened, the production efficiency is effectively improved, the production cost is reduced, and the process flow is simple and easy to industrialize. The nano-scale primary particles obtained by grinding can effectively shorten a transmission path, greatly improve the diffusion rate of ions and electrons, and meanwhile, the lithium iron phosphate material obtained by further screening and grading has the advantages of high low-temperature discharge, good rate capability, high capacity and easiness in processing.
Description
Technical Field
The invention relates to the field of lithium iron phosphate positive electrode material production processes, in particular to a nanoscale lithium iron phosphate positive electrode material capable of improving low-temperature performance in a screening and grading manner and a preparation method thereof.
Background
As one of the first choice of the anode material of the lithium ion power battery, the lithium iron phosphate material has the advantages of stable structure, long service life, good safety, cheap raw materials, no toxicity, environmental protection and the like. However, lithium iron phosphate belongs to an olivine structure, the space is a one-dimensional channel, and the structure determines that the transmission rate of ions and electrons is low, so that the discharge performance is poor in a low-temperature environment.
The main methods for improving the low-temperature performance of the lithium iron phosphate material at present comprise particle nanocrystallization, high-valence cation doping, surface carbon coating and the like. This patent utilizes the sanding to be with the lithium iron phosphate granule nanocrystallization, reaches the purpose that improves material low temperature performance, but conventional sanding need consume for a long time just can grind the granule for a short time, leads to the energy consumption height, and production efficiency is extremely low, and this patent is through optimizing the sanding technology, optimizes the matching to the thick liquids solid content of sanding process, zirconium ball diameter, has greatly shortened the sanding time, improves production efficiency. The lithium iron phosphate material prepared by the method has small particles, uniform size, high performance capacity, good low temperature, excellent rate performance, high production efficiency, low production cost, simple preparation process and easy industrialization.
Disclosure of Invention
In view of the above, the present invention aims to provide a nanoscale lithium iron phosphate positive electrode material capable of improving low-temperature performance by screening and grading, and a preparation method thereof, so as to solve the problems of low transmission rate of electrons and lithium iron phosphate ions and poor discharging performance in a low-temperature environment in the prior art.
In order to achieve the purpose, the technical scheme of the invention is realized as follows:
a preparation method for improving the low-temperature performance of nanoscale lithium iron phosphate by screening and grading comprises the following steps:
(1) mixing a lithium source, iron phosphate and doping elements, and adding a carbon source to obtain a precursor material A;
(2) adding the precursor material A into a dispersion tank for dispersion to obtain slurry B;
(3) transferring the slurry B into a rough grinding machine for sanding, wherein the diameter of zirconium spheres is 0.8-1.0mm, and obtaining slurry C with the granularity D50 being 1.0-2.0 mu m;
(4) transferring the slurry C into a medium-sized grinder for sanding, wherein the diameter of zirconium spheres is 0.4-0.5mm, and obtaining slurry D with the particle size D50 being 0.4-0.8 mu m;
(5) transferring the slurry D into a fine grinding machine for sanding, wherein the diameter of zirconium spheres is 0.2-0.25mm, and the particle size D50 is controlled to be 0.15-0.25 mu m to obtain slurry E;
(6) spray drying the slurry E to obtain lithium iron phosphate precursor powder F;
(7) placing the lithium iron phosphate precursor powder F in an atmosphere furnace to be sintered in an inert atmosphere to obtain a lithium iron phosphate sintered material H;
(8) carrying out jet milling on the lithium iron phosphate sintered material H to obtain a lithium iron phosphate anode material I;
(9) and (3) screening and grading the lithium iron phosphate positive electrode material I, and further controlling the granularity D50 to be 0.5-1.0 mu m to obtain the final lithium iron phosphate positive electrode material.
Further, in the step (1), the molar ratio of the lithium source, the iron phosphate and the doping elements is 0.95-1.05: 1: 0-0.05, wherein the mass of the carbon source is 5-12% of the mass of the total material;
the lithium source includes: one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate;
the iron phosphate comprises: one or two of anhydrous ferric phosphate and dihydrate ferric phosphate;
the doping elements include: one or more of Ti, Zn, Mn, Zr, Mg, Al, V, Cr and Nb;
the carbon source comprises: one or more of glucose, sucrose, citric acid, starch, polyethylene glycol, and polyvinyl alcohol.
Further, in the step (2), pure water is used as a dispersing solvent, the solid content of the slurry is controlled to be 35-45%, and the dispersing time is 30-60 min.
Further, in the step (3), the sanding time is 30-60 min.
Further, in the step (4), the solid content of the slurry is controlled to be 35-45% by mass, and the sanding time is 50-80 min.
Further, in the step (5), the mass percentage of the solid content of the slurry is controlled to be 35-45%, and the sanding time is 50-80 min.
Further, in the step (6), the air inlet temperature of the spray drying is 200-300 ℃, and the air outlet temperature of the spray drying is 70-120 ℃.
Further, in the step (7), heating to 550-800 ℃ at a speed of 5-20 ℃/min, sintering at a constant temperature for 6-12H, and naturally cooling to obtain a lithium iron phosphate sintered material H;
the inert gas includes: one or more of nitrogen, argon and neon.
In the step (8), the jet milling particle size D50 is controlled to be 0.8 to 1.8 μm.
Further, in the step (9), the mesh number used for the sieving classification is 300 to 600 mesh, for example, 300 mesh, 350 mesh, 400 mesh, 450 mesh, 500 mesh, 550 mesh, 600 mesh, etc., but not limited to the recited values, and other values not recited in the range of the values are also applicable.
The invention also aims to provide lithium iron phosphate prepared by the preparation method, and the 1C discharge rate of the battery can reach 150mAh/g when the lithium iron phosphate is used for preparing a finished battery, and the 0.2C capacity retention rate is more than 70% at-20 ℃.
Compared with the prior art, the invention has the following beneficial effects:
according to the invention, through optimizing and matching the diameter of the zirconium ball in the sand grinding process, the particles can be quickly ground to be small, the sand grinding time is greatly shortened, the production efficiency is effectively improved, the production cost is reduced, and the process flow is simple and easy to industrialize. The nano-scale primary particles obtained by grinding can effectively shorten a transmission path, greatly improve the diffusion rate of ions and electrons, and meanwhile, the lithium iron phosphate material obtained by further screening and grading has the advantages of high low-temperature discharge, good rate capability, high capacity and easiness in processing.
Drawings
Fig. 1 is an SEM image of a positive electrode active material prepared in example 1 of the present invention;
fig. 2 is an SEM image of the positive electrode active material prepared in comparative example 1 of the present invention;
fig. 3 is a particle size distribution diagram of a positive electrode active material prepared in example 1 of the present invention;
fig. 4 is a particle size distribution diagram of the positive electrode active material prepared in comparative example 1 of the present invention.
Detailed Description
Unless defined otherwise, technical terms used in the following examples have the same meanings as commonly understood by one of ordinary skill in the art to which the present invention belongs. The test reagents used in the following examples, unless otherwise specified, are all conventional biochemical reagents; the experimental methods are conventional methods unless otherwise specified.
The present invention will be described in detail with reference to the following examples and accompanying drawings.
Example 1:
mixing a lithium source, iron phosphate and doping elements according to a molar ratio of 0.95: 1: 0.01, adding a carbon source according to 9 percent of the total mass of the material, adding deionized water according to 40 percent of solid content, dispersing for 60min, then transferring to a sand mill with a zirconium ball diameter of 0.8mm, carrying out coarse grinding for 60min, then transferring to a sand mill with a zirconium ball diameter of 0.4mm, carrying out medium grinding for 50min, finally transferring to a sand mill with a zirconium ball diameter of 0.2mm, carrying out fine grinding for 60min, controlling the particle size D50 to be 0.22-0.25 mu m, then carrying out spray drying to obtain a material A, placing the material A in an atmosphere furnace, sintering, and carrying out N-phase sintering in an N atmosphere furnace2Heating to 550 ℃ at the temperature of 5 ℃/min under the atmosphere and sintering at constant temperature of 12And h, naturally cooling to obtain a material B, carrying out jet milling on the material B, controlling the particle size D50 to be 1.0-1.2 mu m, and then carrying out screening classification through a 400-mesh screen, controlling the particle size D50 to be 0.7-0.8 mu m, thus obtaining the lithium iron phosphate cathode material.
Example 2:
lithium source, iron phosphate and doping elements are mixed according to a molar ratio of 1.0: 1: 0.025, adding a carbon source accounting for 5 percent of the total mass of the material, adding deionized water according to 40 percent of solid content, dispersing for 45min, then transferring to a sand mill with a zirconium ball diameter of 0.8mm, carrying out coarse grinding for 60min, then transferring to a sand mill with a zirconium ball diameter of 0.4mm, carrying out medium grinding for 60min, finally transferring to a sand mill with a zirconium ball diameter of 0.2mm, carrying out fine grinding for 50min, controlling the particle size D50 to be 0.18-0.22 mu m, then carrying out spray drying to obtain a material A, placing the material A in an atmosphere furnace, sintering, and carrying out N-phase sintering in an N atmosphere furnace2Heating to 650 ℃ at a temperature of 15 ℃/min under the atmosphere, sintering for 9h at a constant temperature, naturally cooling to obtain a material B, carrying out jet milling on the material B, controlling the particle size D50 to be 1.1-1.4 mu m, and then carrying out screening classification by using a 325-mesh screen, controlling the particle size D50 to be 0.9-1.0 mu m, thereby obtaining the lithium iron phosphate cathode material.
Example 3:
mixing a lithium source, iron phosphate and doping elements according to a molar ratio of 1.05: 1: 0.05, adding a carbon source accounting for 12 percent of the total mass of the material, adding deionized water according to 40 percent of solid content for dispersing for 30min, then transferring to a sand mill with a zirconium ball diameter of 0.8mm for coarse grinding for 50min, then transferring to a sand mill with a zirconium ball diameter of 0.4mm for medium grinding for 60min, finally transferring to a sand mill with a zirconium ball diameter of 0.2mm for fine grinding for 80min, controlling the particle size D50 to be 0.15-0.18 mu m, then spraying and drying to obtain a material A, placing the material A in an atmosphere furnace for sintering, and sintering in an N atmosphere furnace2Heating to 750 ℃ at a speed of 10 ℃/min under the atmosphere, sintering at the constant temperature for 6h, naturally cooling to obtain a material B, carrying out jet milling on the material B, controlling the particle size D50 to be 0.8-1.1 mu m, and then carrying out screening classification by using a 500-mesh screen, controlling the particle size D50 to be 0.5-0.6 mu m, thereby obtaining the lithium iron phosphate anode material.
Example 4:
lithium source, ferric phosphate and doping elements are mixed according to the molar ratio1.02: 1: 0.03, adding a carbon source accounting for 8 percent of the total mass of the material, adding deionized water according to 40 percent of solid content for dispersing for 30min, then transferring to a sand mill with a zirconium ball diameter of 0.8mm for coarse grinding for 60min, then transferring to a sand mill with a zirconium ball diameter of 0.4mm for medium grinding for 50min, finally transferring to a sand mill with a zirconium ball diameter of 0.2mm for fine grinding for 50min, controlling the particle size D50 to be 0.2-0.22 mu m, then spraying and drying to obtain a material A, placing the material A in an atmosphere furnace for sintering, and sintering in an N atmosphere furnace2Heating to 720 ℃ at a speed of 12 ℃/min under the atmosphere, sintering for 8h at a constant temperature, naturally cooling to obtain a material B, carrying out jet milling on the material B, controlling the particle size D50 to be 1.0-1.3 mu m, and then carrying out screening classification by using a 300-mesh screen, controlling the particle size D50 to be 0.6-0.7 mu m, thereby obtaining the lithium iron phosphate anode material.
Example 5:
mixing a lithium source, iron phosphate and doping elements according to a molar ratio of 1.015: 1: 0.04, adding a carbon source accounting for 7 percent of the total mass of the material, adding deionized water according to 40 percent of solid content to disperse for 40min, then transferring to a sand mill with a zirconium ball diameter of 0.8mm to carry out coarse grinding for 60min, then transferring to a sand mill with a zirconium ball diameter of 0.4mm to carry out medium grinding for 80min, finally transferring to a sand mill with a zirconium ball diameter of 0.2mm to carry out fine grinding for 50min, controlling the particle size D50 to be 0.18-0.22 mu m, then spraying and drying to obtain a material A, placing the material A in an atmosphere furnace to sinter, and sintering in an N atmosphere furnace2Heating to 680 ℃ at the temperature of 11 ℃/min under the atmosphere, sintering at the constant temperature for 10h, naturally cooling to obtain a material B, carrying out jet milling on the material B, controlling the particle size D50 to be 1.2-1.4 mu m, and then carrying out screening classification through a 400-mesh screen, controlling the particle size D50 to be 0.8-0.9 mu m, so as to obtain the lithium iron phosphate cathode material.
Example 6:
mixing a lithium source, iron phosphate and doping elements according to a molar ratio of 0.97: 1: 0.03, adding a carbon source accounting for 8 percent of the total mass of the materials, adding deionized water according to 40 percent of the solid content for dispersing for 30min, then transferring to a sand mill with a zirconium ball diameter of 0.8mm for coarse grinding for 50min, then transferring to a sand mill with a zirconium ball diameter of 0.4mm for medium grinding for 70min, finally transferring to a sand mill with a zirconium ball diameter of 0.2mm for fine grinding for 70min, and controlling the granularity D50-0.16-0.2 μm, spray drying to obtain material A, sintering in atmosphere furnace, and adding N2Heating to 600 ℃ at a speed of 5 ℃/min under the atmosphere, sintering for 12h at a constant temperature, naturally cooling to obtain a material B, carrying out jet milling on the material B, controlling the particle size D50 to be 1.1-1.3 mu m, and then carrying out screening classification by using a 300-mesh screen, controlling the particle size D50 to be 0.7-0.8 mu m, thereby obtaining the lithium iron phosphate anode material.
Comparative example 1:
lithium source, ferric phosphate and doping elements are mixed according to a molar ratio of 1:1: 0.02, adding sucrose accounting for 10 percent of the total mass of the materials, adding deionized water according to 40 percent of solid content, dispersing for 40min, transferring to a sand mill with a zirconium ball diameter of 0.4mm, sanding for 6h, controlling the particle size D50 to be 0.5-0.55 mu m, performing spray drying to obtain a lithium iron phosphate precursor, placing the lithium iron phosphate precursor in N2And (2) sintering the mixture for 15 hours at a constant temperature of 700 ℃ in an atmosphere furnace, cooling the mixture, then carrying out jet milling on the sintered material, controlling the particle size D50 to be 1.3-1.6 mu m, and then carrying out screening classification by using a 120-mesh screen, controlling the particle size D50 to be 1.2-1.5 mu m, thus obtaining the lithium iron phosphate cathode material.
Comparative example 2:
mixing a lithium source, iron phosphate and doping elements according to a molar ratio of 0.99: 1: 0.01, adding sucrose accounting for 9 percent of the total mass of the materials, adding deionized water according to 40 percent of solid content for dispersing for 40min, transferring the materials to a sand mill with a zirconium ball diameter of 0.4mm, then performing sand milling for 6h, controlling the particle size D50 to be 0.45-0.5 mu m, performing spray drying to obtain a lithium iron phosphate precursor, placing the lithium iron phosphate precursor in N2And (3) sintering the mixture for 7 hours at a constant temperature of 740 ℃ in an atmosphere furnace, cooling, and then carrying out jet milling on the sintered material, wherein the granularity is controlled to be D50 to be 1.1-1.4 mu m, so as to obtain the lithium iron phosphate cathode material.
Comparative example 3:
lithium source, ferric phosphate and doping elements are mixed according to a molar ratio of 1.02: 1: 0.015 percent of the total mass of the materials are mixed, sucrose is added according to 12 percent of the total mass of the materials, deionized water is added according to 40 percent of the solid content for dispersion for 60min, then the materials are transferred to a sand mill with a zirconium ball diameter of 0.8mm for coarse grinding for 60min, and then the materials are transferred to a zirconium ball with a diameter of 0.4mmThe sand mill is used for middle milling for 60min, finally the mixture is transferred into a sand mill with a zirconium ball diameter of 0.2mm for fine milling for 60min, the granularity is controlled to be D50 to be 0.2-0.22 mu m, then spray drying is carried out to obtain a lithium iron phosphate precursor, and the lithium iron phosphate precursor is placed in N2And sintering the mixture for 8 hours at a constant temperature of 700 ℃ in an atmosphere furnace, cooling, and then carrying out jet milling on the sintered material, wherein the particle size is controlled to be D50-1.0-1.2 mu m, so as to obtain the lithium iron phosphate cathode material.
Performance testing
(1) Preparation of the Battery
Preparation of the Positive electrode
93 g of positive electrode active materials LiFePO obtained in examples 1 to 3 and comparative example 1 were added to the reaction solution45 g of polyvinylidene fluoride (PVDF) as a binder and 3 g of acetylene black as a conductive agent were added to 85 g of N-methylpyrrolidone, and then stirred in a vacuum stirrer to form a uniform positive electrode slurry. The positive electrode slurry was uniformly coated on both sides of an aluminum foil having a thickness of 16 μm, and then dried at 118 ℃, rolled, and cut to obtain a positive electrode having a size of 540 × 43.5 mm, which contained about 6.5 g of an active ingredient LiFePO4。
Preparation of the negative electrode
93 g of natural graphite as a negative active ingredient, 1.4 g of CMC and 2g of carbon black as a conductive agent are added into 120 g of deionized water, then the mixture is stirred uniformly in a vacuum stirrer, and finally 1.6 g of SBR is added to be stirred slowly for 40 minutes to form uniform negative electrode slurry. The negative electrode slurry was uniformly coated on both sides of a copper foil having a thickness of 8 μm, and then dried at 90 c, rolled, and cut to obtain a negative electrode having a size of 500 × 44 mm, which contained about 3.7 g of natural graphite as an active ingredient.
Assembly of a battery
Respectively winding the positive electrode, the negative electrode and the polyethylene film into a pole core of a square lithium ion battery, and then winding LiPF6The electrolyte was dissolved in a mixed solvent of EC/EMC/DEC ═ 1:1:1 at a concentration of 1 mol/liter to prepare a nonaqueous electrolyte, and the electrolyte was poured into a battery aluminum case at an amount of 3.2g/Ah and sealed to prepare lithium ion secondary batteries a1-A3 and B1, respectively.
(2) Battery performance testing
Respectively placing the prepared lithium ion batteries A, B, C, D, E on a test cabinet, and carrying out constant-current and constant-voltage charging at 1C in a constant temperature box of 25 ℃, wherein the upper limit of charging is 3.65V; after standing for 20 minutes, discharging from 3.65 volts to 2.0 volts at a current of 1C, recording the first discharge capacity of the battery, and then carrying out constant-current constant-voltage charging at a current of 1C, wherein the upper charge limit is 3.65 volts.
Placing the charged lithium ion battery A, B, C, D, E in a low temperature box, standing for 4 hours, discharging at a rate of 1C, wherein the voltage range is 2.0-3.65V, and recording the cyclic discharge capacity, wherein the specific data are shown in the following table 1:
TABLE 1 comparison of Low temperature Performance data for full cells
As can be seen from the SEM accompanying drawing of the specification, the primary particles of the cathode material prepared by the method are smaller, and as can be seen from the particle size diagram of the Malvern 3000 of the specification, the secondary crushed particles of the cathode material prepared by the method account for more than small particles; from the data in the table, it can be analyzed that the initial discharge specific capacity and the low-temperature performance of the battery prepared by the anode material prepared by the method are far higher than those of the reference battery prepared by the comparative example, and the battery also has excellent low-temperature performance.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.
Claims (10)
1. A preparation method of a nanoscale lithium iron phosphate anode material capable of improving low-temperature performance in a screening and grading manner is characterized by comprising the following steps:
(1) mixing a lithium source, iron phosphate and doping elements, and adding a carbon source to obtain a precursor material A;
(2) adding the precursor material A into a dispersion tank for dispersion to obtain slurry B;
(3) transferring the slurry B into a rough grinding machine for sanding, wherein the diameter of zirconium spheres is 0.8-1.0mm, and obtaining slurry C with the granularity D50 being 1.0-2.0 mu m;
(4) transferring the slurry C into a medium-sized grinder for sanding, wherein the diameter of zirconium spheres is 0.4-0.5mm, and obtaining slurry D with the particle size D50 being 0.4-0.8 mu m;
(5) transferring the slurry D into a fine grinding machine for sanding, wherein the diameter of zirconium spheres is 0.2-0.25mm, and the particle size D50 is controlled to be 0.15-0.25 mu m to obtain slurry E;
(6) spray drying the slurry E to obtain lithium iron phosphate precursor powder F;
(7) placing the lithium iron phosphate precursor powder F in an atmosphere furnace to be sintered in an inert atmosphere to obtain a lithium iron phosphate sintered material H;
(8) carrying out jet milling on the lithium iron phosphate sintered material H to obtain a lithium iron phosphate anode material I;
(9) and (3) screening and grading the lithium iron phosphate positive electrode material I, and further controlling the granularity D50 to be 0.5-1.0 mu m to obtain the final lithium iron phosphate positive electrode material.
2. The preparation method of the nanoscale lithium iron phosphate cathode material capable of improving low-temperature performance in a screening and grading manner according to claim 1, wherein in the step (1), the molar ratio of the lithium source to the iron phosphate to the doping elements is 0.95-1.05: 1: 0-0.05, wherein the mass of the carbon source is 5-12% of the mass of the total material;
the lithium source includes: one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate;
the iron phosphate comprises: one or two of anhydrous ferric phosphate and dihydrate ferric phosphate;
the doping elements include: one or more of Ti, Zn, Mn, Zr, Mg, Al, V, Cr and Nb;
the carbon source comprises: one or more of glucose, sucrose, citric acid, starch, polyethylene glycol, and polyvinyl alcohol.
3. The preparation method of the nanoscale lithium iron phosphate anode material with the low-temperature performance improved through screening and grading according to claim 1, characterized in that in the step (2), pure water is used as a dispersing solvent, the mass percentage of the solid content of the slurry is controlled to be 35-45%, and the dispersing time is 30-60 min.
4. The preparation method of the nanoscale lithium iron phosphate cathode material with the low-temperature performance improved through screening and classification as claimed in claim 1, wherein in the step (3), the sanding time is 30-60 min.
5. The preparation method of the nanoscale lithium iron phosphate cathode material with the low-temperature performance improved through screening and classification as claimed in claim 1, wherein in the step (4), the mass percentage of the solid content of the slurry is controlled to be 35-45%, and the sanding time is 50-80 min.
6. The preparation method of the nanoscale lithium iron phosphate cathode material with the low-temperature performance improved through screening and classification as claimed in claim 1, wherein in the step (5), the solid content of the slurry is controlled to be 35-45%, and the sanding time is 50-80 min.
7. The preparation method of the nanoscale lithium iron phosphate positive electrode material with the low-temperature performance improved through screening and grading according to claim 1, wherein in the step (6), the inlet air temperature of spray drying is 200-300 ℃, and the outlet air temperature of spray drying is 70-120 ℃.
8. The preparation method of the nanoscale lithium iron phosphate anode material with the low-temperature performance improved in a screening and grading manner as claimed in claim 1, wherein in the step (7), the temperature is raised to 550-800 ℃ at a rate of 5-20 ℃/min, the nanoscale lithium iron phosphate anode material is sintered for 6-12 hours at a constant temperature, and the temperature is naturally cooled to obtain a lithium iron phosphate sintered material H;
the inert gas includes: one or more of nitrogen, argon and neon.
9. The method for preparing a nanoscale lithium iron phosphate cathode material with improved low-temperature performance by screening and classification as claimed in claim 1, wherein in step (8), the jet milling controlled particle size D50 is 0.8-1.8 μm.
10. The lithium iron phosphate prepared by the preparation method according to any one of claims 1 to 9, wherein the lithium iron phosphate is used for preparing a finished battery, and the 1C discharge rate of the battery can reach 150mAh/g, and the 0.2C capacity retention rate is more than 70% at-20 ℃.
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