CN114933290A - Anhydrous ferric phosphate and ferric oxide mixture, synthesis method thereof, lithium iron phosphate, preparation method and application thereof - Google Patents
Anhydrous ferric phosphate and ferric oxide mixture, synthesis method thereof, lithium iron phosphate, preparation method and application thereof Download PDFInfo
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- CN114933290A CN114933290A CN202210721616.2A CN202210721616A CN114933290A CN 114933290 A CN114933290 A CN 114933290A CN 202210721616 A CN202210721616 A CN 202210721616A CN 114933290 A CN114933290 A CN 114933290A
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- iron phosphate
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- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 title claims abstract description 51
- 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 51
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 title claims abstract description 41
- 239000000203 mixture Substances 0.000 title claims abstract description 36
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 238000002360 preparation method Methods 0.000 title claims abstract description 19
- 239000005955 Ferric phosphate Substances 0.000 title claims abstract description 15
- 229940032958 ferric phosphate Drugs 0.000 title claims abstract description 15
- 229910000399 iron(III) phosphate Inorganic materials 0.000 title claims abstract description 15
- 238000001308 synthesis method Methods 0.000 title abstract description 3
- 229910000398 iron phosphate Inorganic materials 0.000 claims abstract description 26
- 238000005245 sintering Methods 0.000 claims abstract description 24
- 238000000034 method Methods 0.000 claims abstract description 23
- 229910019142 PO4 Inorganic materials 0.000 claims abstract description 18
- 239000010452 phosphate Substances 0.000 claims abstract description 18
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims abstract description 16
- 230000003647 oxidation Effects 0.000 claims abstract description 15
- 238000007254 oxidation reaction Methods 0.000 claims abstract description 15
- 229910001448 ferrous ion Inorganic materials 0.000 claims abstract description 13
- 239000008247 solid mixture Substances 0.000 claims abstract description 13
- 239000000725 suspension Substances 0.000 claims abstract description 10
- 238000006243 chemical reaction Methods 0.000 claims abstract description 8
- 238000002156 mixing Methods 0.000 claims abstract description 8
- 230000001590 oxidative effect Effects 0.000 claims abstract description 8
- 239000000463 material Substances 0.000 claims abstract description 7
- 238000004519 manufacturing process Methods 0.000 claims abstract description 6
- 239000002243 precursor Substances 0.000 claims description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 238000000498 ball milling Methods 0.000 claims description 11
- 239000002245 particle Substances 0.000 claims description 11
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 claims description 11
- 238000001035 drying Methods 0.000 claims description 9
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 8
- 229910052799 carbon Inorganic materials 0.000 claims description 8
- 238000010532 solid phase synthesis reaction Methods 0.000 claims description 7
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 6
- 239000001488 sodium phosphate Substances 0.000 claims description 6
- 238000005507 spraying Methods 0.000 claims description 6
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 6
- 239000003963 antioxidant agent Substances 0.000 claims description 5
- 230000003078 antioxidant effect Effects 0.000 claims description 5
- 239000005696 Diammonium phosphate Substances 0.000 claims description 4
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 4
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 4
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 4
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 4
- 238000000227 grinding Methods 0.000 claims description 4
- 229910052698 phosphorus Inorganic materials 0.000 claims description 4
- 239000011574 phosphorus Substances 0.000 claims description 4
- 238000012216 screening Methods 0.000 claims description 4
- MYMOFIZGZYHOMD-UHFFFAOYSA-N Dioxygen Chemical compound O=O MYMOFIZGZYHOMD-UHFFFAOYSA-N 0.000 claims description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 3
- 239000007921 spray Substances 0.000 claims description 3
- 229910002651 NO3 Inorganic materials 0.000 claims description 2
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 2
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 2
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 2
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims description 2
- ZRIUUUJAJJNDSS-UHFFFAOYSA-N ammonium phosphates Chemical compound [NH4+].[NH4+].[NH4+].[O-]P([O-])([O-])=O ZRIUUUJAJJNDSS-UHFFFAOYSA-N 0.000 claims description 2
- BNIILDVGGAEEIG-UHFFFAOYSA-L disodium hydrogen phosphate Chemical compound [Na+].[Na+].OP([O-])([O-])=O BNIILDVGGAEEIG-UHFFFAOYSA-L 0.000 claims description 2
- 229910000397 disodium phosphate Inorganic materials 0.000 claims description 2
- 235000019800 disodium phosphate Nutrition 0.000 claims description 2
- 229960002089 ferrous chloride Drugs 0.000 claims description 2
- 239000011790 ferrous sulphate Substances 0.000 claims description 2
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 2
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 2
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 2
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 2
- 239000006012 monoammonium phosphate Substances 0.000 claims description 2
- 229910000403 monosodium phosphate Inorganic materials 0.000 claims description 2
- 235000019799 monosodium phosphate Nutrition 0.000 claims description 2
- AJPJDKMHJJGVTQ-UHFFFAOYSA-M sodium dihydrogen phosphate Chemical compound [Na+].OP(O)([O-])=O AJPJDKMHJJGVTQ-UHFFFAOYSA-M 0.000 claims description 2
- 239000002904 solvent Substances 0.000 claims description 2
- RYFMWSXOAZQYPI-UHFFFAOYSA-K trisodium phosphate Chemical compound [Na+].[Na+].[Na+].[O-]P([O-])([O-])=O RYFMWSXOAZQYPI-UHFFFAOYSA-K 0.000 claims description 2
- 229910000406 trisodium phosphate Inorganic materials 0.000 claims description 2
- 235000019801 trisodium phosphate Nutrition 0.000 claims description 2
- 238000010298 pulverizing process Methods 0.000 claims 2
- 238000009413 insulation Methods 0.000 claims 1
- 230000008569 process Effects 0.000 abstract description 7
- 230000032683 aging Effects 0.000 abstract description 3
- 230000015572 biosynthetic process Effects 0.000 abstract description 3
- 238000004537 pulping Methods 0.000 abstract description 3
- 238000003786 synthesis reaction Methods 0.000 abstract description 3
- 230000002194 synthesizing effect Effects 0.000 abstract description 3
- 239000007790 solid phase Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 17
- 239000008367 deionised water Substances 0.000 description 10
- 229910021641 deionized water Inorganic materials 0.000 description 10
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 6
- 239000013078 crystal Substances 0.000 description 6
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 description 5
- 235000011114 ammonium hydroxide Nutrition 0.000 description 5
- 238000005056 compaction Methods 0.000 description 5
- 229910052742 iron Inorganic materials 0.000 description 5
- 239000000843 powder Substances 0.000 description 5
- 239000000047 product Substances 0.000 description 5
- 238000001694 spray drying Methods 0.000 description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 4
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 4
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 4
- 235000006708 antioxidants Nutrition 0.000 description 4
- 239000011324 bead Substances 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 239000000706 filtrate Substances 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- 238000003756 stirring Methods 0.000 description 4
- 229910052726 zirconium Inorganic materials 0.000 description 4
- PEDCQBHIVMGVHV-UHFFFAOYSA-N Glycerine Chemical compound OCC(O)CO PEDCQBHIVMGVHV-UHFFFAOYSA-N 0.000 description 3
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 3
- 229960005070 ascorbic acid Drugs 0.000 description 3
- 235000010323 ascorbic acid Nutrition 0.000 description 3
- 239000011668 ascorbic acid Substances 0.000 description 3
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 3
- 238000002425 crystallisation Methods 0.000 description 3
- 230000008025 crystallization Effects 0.000 description 3
- 239000002270 dispersing agent Substances 0.000 description 3
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 3
- 239000001301 oxygen Substances 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000004321 preservation Methods 0.000 description 3
- 238000001878 scanning electron micrograph Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- SPFMQWBKVUQXJV-BTVCFUMJSA-N (2r,3s,4r,5r)-2,3,4,5,6-pentahydroxyhexanal;hydrate Chemical compound O.OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C=O SPFMQWBKVUQXJV-BTVCFUMJSA-N 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 239000007864 aqueous solution Substances 0.000 description 2
- 229960000673 dextrose monohydrate Drugs 0.000 description 2
- 238000001914 filtration Methods 0.000 description 2
- 239000007789 gas Substances 0.000 description 2
- 238000005469 granulation Methods 0.000 description 2
- 230000003179 granulation Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 230000007935 neutral effect Effects 0.000 description 2
- 229910052757 nitrogen Inorganic materials 0.000 description 2
- 239000011164 primary particle Substances 0.000 description 2
- 238000007873 sieving Methods 0.000 description 2
- 239000007787 solid Substances 0.000 description 2
- 238000005406 washing Methods 0.000 description 2
- 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 description 1
- 241000282414 Homo sapiens Species 0.000 description 1
- 239000002202 Polyethylene glycol Substances 0.000 description 1
- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 description 1
- 239000010405 anode material Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 239000012065 filter cake Substances 0.000 description 1
- 229960001031 glucose Drugs 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 229920001223 polyethylene glycol Polymers 0.000 description 1
- 239000002244 precipitate Substances 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000000967 suction filtration Methods 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
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- 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
- C01B25/37—Phosphates of heavy metals
- C01B25/375—Phosphates of heavy metals of iron
-
- 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G49/00—Compounds of iron
- C01G49/02—Oxides; Hydroxides
- C01G49/06—Ferric oxide [Fe2O3]
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- 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
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
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- 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
- C01P2004/61—Micrometer sized, i.e. from 1-100 micrometer
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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Abstract
The invention discloses a mixture of anhydrous ferric phosphate and ferric oxide and a synthesis method thereof, lithium iron phosphate and a preparation method and application thereof, wherein the method for synthesizing the mixture of anhydrous ferric phosphate and ferric oxide by a solid phase comprises the following steps: mixing a solution containing ferrous ions and a solution containing phosphate radical according to a molar ratio of 1.50 (0.95-1.05) for reaction to obtain a suspension; separating the suspension to obtain a solid mixture, and then placing the solid mixture at the temperature of 180-300 ℃ for oxidizing and sintering to obtain the anhydrous ferric phosphate and ferric oxide mixture; and after the oxidation sintering, carrying out secondary oxidation sintering at 550-650 ℃, so that the steps of pulping, aging and the like are omitted, the synthesis period is short, the process is simple, the manufacturing cost is saved, the obtained anhydrous iron phosphate is doped with ferric oxide in a nano-scale manner, and the performance of the battery material is finally improved.
Description
Technical Field
The invention relates to the technical field of battery materials, in particular to a mixture of anhydrous iron phosphate and ferric oxide, a synthetic method of the mixture, lithium iron phosphate, a preparation method of the lithium iron phosphate and application of the lithium iron phosphate.
Background
Energy and environmental problems become more serious, and petrochemical energy is less and less, so that the requirements of human beings will not be met in the future, and therefore, the search for new alternative energy is urgent. In recent years, electric vehicles, hybrid electric vehicles, and the like have been rapidly developed, and lithium batteries have been absolutely superior as a high-performance secondary green battery. The lithium iron phosphate battery has the advantages of wide raw material source, no environmental pollution, good thermal stability, high safety performance and the like, and is used as an ideal anode material.
The current mainstream is to prepare lithium iron phosphate with iron phosphate, wherein iron phosphate can provide an iron source and a phosphorus source simultaneously in the process of synthesizing the lithium iron phosphate, the volume change of a unit cell is small and is only about 6.81%, and the stability of the material is favorably improved, so that the iron phosphate becomes a core precursor for preparing the lithium iron phosphate cathode material.
But the compaction density of the lithium iron phosphate prepared from the iron phosphate reaches 2.8g/cm 3 The above is difficult, and the sintering temperature and the heat preservation time can reach 2.8g/cm 3 The compaction density of (a) and the need to add more carbon source, the cost is greatly increased.
In order to solve the problem, the iron oxide is selected to be doped and the generation of gas is reduced to reach the lithium iron phosphate with high compaction density.
Disclosure of Invention
Aiming at the problem of low compacted density of lithium iron phosphate obtained by the existing preparation method, the invention provides a method for solid-phase synthesis of a mixture of anhydrous iron phosphate and ferric oxide.
The technical method comprises the following steps: a method for solid phase synthesis of a mixture of anhydrous iron phosphate and iron oxide, the method comprising:
mixing a solution containing ferrous ions and a solution containing phosphate radicals according to a molar ratio of 1.50 (0.95-1.05) to react to obtain a suspension;
separating the suspension to obtain a solid mixture, and then placing the solid mixture at the temperature of 180-300 ℃ for oxidizing and sintering to obtain the anhydrous ferric phosphate and ferric oxide mixture;
performing a second oxidation sintering at 550-650 ℃ after the oxidation sintering;
mixing and reacting the prepared anhydrous iron phosphate and iron oxide mixture, lithium phosphate and a carbon-containing antioxidant, and drying to obtain a lithium iron phosphate precursor;
wherein: the mol ratio of the iron element, the lithium element, the phosphorus element and the carbon element is (0.97-1.00): (0.98-1.05):1.00 (0.52-0.65);
and (3) preserving the heat of the lithium iron phosphate precursor at the temperature of 700-850 ℃ in an oxygen-free environment to obtain the lithium iron phosphate.
The invention has the beneficial effects that:
1. the invention can obtain two iron sources of anhydrous ferric phosphate and ferric oxide, and the particle sizes are matched.
2. Compared with the traditional preparation process of anhydrous iron phosphate, the preparation method has the advantages of saving the steps of pulping, aging and the like, having short synthesis period and simple process, saving the manufacturing cost, and greatly saving the cost by adopting oxygen to replace hydrogen peroxide to oxidize ferrous iron.
3. According to the invention, only the carbon source in the precursor is decomposed to release gas, so that the introduction amount of the inert gas is reduced, the yield of the prepared lithium iron phosphate is high, the production efficiency is greatly improved, and the production cost is saved.
4. The invention adopts two different iron sources to prepare the lithium iron phosphate, which has great difference on the principle of crystal generation, and the larger blocky anhydrous ferric phosphate and the small-particle ferric oxide react with the lithium phosphate and the glucose respectively to generate the lithium iron phosphate with greatly different mechanisms and rates, thereby forming the lithium iron phosphate with different particle sizes and matched sizes, and adding the primary particles of the lithium iron phosphateThe surface is regular, the particles are spherical, the compaction density of the lithium iron phosphate is greatly improved, and the compaction density of the prepared lithium iron phosphate can reach 2.8g/cm 3 Thereby achieving excellent conductivity and stability, having good application prospect as the electrode material of the lithium battery and being worth popularizing.
Drawings
FIG. 1 is a flow chart of the preparation of the present invention;
FIG. 2 is an SEM scanning electron micrograph (30000 times) of a mixture of anhydrous iron phosphate and iron oxide prepared in example 1;
fig. 3 is a SEM scanning electron micrograph (50000 times) of lithium iron phosphate prepared in example 1;
fig. 4 is an XRD pattern of lithium iron phosphate prepared in example 2.
Detailed Description
In order to solve the problem of low compacted density of lithium iron phosphate obtained by the existing preparation method, the applicant proposes a method for synthesizing anhydrous iron phosphate and ferric oxide by adopting a solid phase, as shown in fig. 1: the method comprises the following steps:
s1, mixing a solution containing ferrous ions and a solution containing phosphate radicals according to a molar ratio of 1.50 (0.95-1.05) to react to obtain a suspension;
in order to avoid insufficient reaction caused by coating of the precipitate, the solution containing phosphate is added into the solution containing ferrous ions in a spraying mode in the step, and the flow rate is 0.01-1000 liters/minute;
wherein: the concentration of the solution containing ferrous ions is 1.0-2.5mol/L, and the ferrous ions are derived from at least one of ferrous sulfate, ferrous chloride and ferrous nitrate; in order to avoid the ferrous ions from being oxidized, the solution containing the ferrous ions also comprises an antioxidant, preferably ascorbic acid, and the addition amount of the antioxidant is 0.1-5.0 wt% of the ferrous ion source substance;
the concentration of the solution containing phosphate radical is 2.5-5.0mol/L, and the phosphate radical is derived from at least one of monoammonium phosphate, diammonium phosphate, triammonium phosphate or monosodium phosphate, disodium phosphate and trisodium phosphate; in order to sufficiently disperse the phosphate-derived substance during the preparation of the solution containing phosphate, a dispersant is added, the dispersant being used in an amount of 0.1 to 3.0 wt% based on the phosphate-derived substance, the dispersant being at least one selected from the group consisting of ethanol, glycerol and polyethylene glycol.
After the reaction is finished, ammonia water or sodium hydroxide with the mass fraction of 10% -20% is used for adjusting the pH value of the solution to 5.5-9.0, ammonia water is preferred, the ammonia water is weak base and has low concentration, the pH value is easy to control, and the pH value jump of a contact surface is avoided.
S2, separating the suspension to obtain a solid mixture, and then oxidizing and sintering the solid mixture at the temperature of 300 ℃ of 180 ℃ to obtain the anhydrous iron phosphate and iron oxide mixture.
In the step, the separation mode is suction filtration, and the filter cake is repeatedly cleaned for many times; for sufficient oxidation, the solid mixture is dissolved before oxidation and then milled to a particle size of 0.1-1.0 μm and a solids content of 40-50%, preferably by ball milling, more preferably in a ball mill;
in order to save the dehydration cost, the process of spray drying granulation is also included after the ball milling, the drying temperature is 120-180 ℃, and the time for removing the crystallization water by oxidizing sintering and the complete removal of the crystallization water can also be saved.
The method and the device have the advantages that the oxidation is carried out in the air in the process of removing the crystal water and sintering, and the cost is greatly saved.
S3, performing secondary oxidation sintering at the temperature of 550-650 ℃ after the oxidation sintering.
The second time of oxidizing and sintering is carried out in pure oxygen for 2-5 hours, and the pure oxygen replaces hydrogen peroxide in the traditional process, thereby greatly saving the cost.
The preparation method has the following advantages: 1. the precursor with the particle size distribution matched with the sizes of different crystal forms of the anhydrous ferric phosphate and the ferric oxide can be obtained.
2. Compared with the traditional preparation process of the anhydrous iron phosphate, the preparation process has the advantages of saving the steps of pulping, aging and the like, having short synthesis period and simple process, saving the manufacturing cost, and finally improving the performance of the battery material because the obtained anhydrous iron phosphate is doped with ferric oxide in a nanometer level.
Based on the same inventive concept, the application also discloses a preparation method of lithium iron phosphate, as shown in fig. 1, the preparation method comprises the following steps:
s1, mixing and dissolving the prepared anhydrous ferric phosphate and ferric oxide mixture, lithium phosphate and a carbon-containing antioxidant in a solvent for reaction, and drying to obtain a lithium iron phosphate precursor;
wherein: the mol ratio of the iron element, the lithium element, the phosphorus element and the carbon element is (0.97-1.00): (0.98-1.05):1.00 (0.52-0.65);
for full drying, grinding is carried out simultaneously with the mixing reaction until the particle size is 0.2-0.5 μm and the solid content is 40-50%, a ball milling mode is preferred, grinding is carried out in a star ball mill for thorough removal of crystal water, and spray drying granulation is carried out after grinding is finished, wherein the drying time is 120-180 ℃;
s2, preserving the heat of the lithium iron phosphate precursor at the temperature of 700-850 ℃ in an oxygen-free environment to obtain the lithium iron phosphate; in this step: the anaerobic environment is carried out in an inert environment, the crushing and the screening by a 300-mesh and 500-mesh screen are carried out after the heat preservation, the heat preservation time is 3-8 hours, and the crystallization water is conveniently and thoroughly removed.
The compacted density of the lithium iron phosphate prepared by the method can reach 2.8g/cm 3 Thereby achieving excellent conductivity and stability.
Example 1
This example prepared an anhydrous iron phosphate and iron oxide mixture comprising the steps of:
s1, preparing a ferrous salt aqueous solution
834g of analytically pure ferrous sulfate heptahydrate and 1.0g of ascorbic acid are added to 1000g of deionized water and dissolved at 30 ℃ with stirring at 380 rpm.
S2, preparing phosphate solution
264g of analytically pure diammonium phosphate and 1.0g of ethanol were added to 500g of deionized water and dissolved with stirring at 30 ℃.
S3. reaction
Transferring the phosphate solution into a sprinkling can, and uniformly sprinkling for 8 minutesAdding the mixture into iron liquid, reacting for 20 minutes, adjusting the pH value of 10-20% ammonia water solution to 6.5 by using a spray can, reacting for 30 minutes, washing and filtering by deionized water until the filtrate is neutral, transferring the filtrate to a ball milling tank, adding 2006g of zirconium beads and 400g of deionized water, and ball milling the filtrate by using a planetary ball mill until d is reached 50 0.4 μm, the slurry was spray dried at 180 ℃ to obtain a powder.
S4, removing crystal water
And (3) putting the powder into a tube furnace, introducing air, preserving heat for 4 hours at 200 ℃, introducing oxygen, preserving heat for 3 hours at 600 ℃, and naturally cooling to obtain the anhydrous iron phosphate and iron oxide mixture.
SEM scanning electron micrographs (30000 times) of the mixture of anhydrous iron phosphate and iron oxide prepared in this example are shown in fig. 2, and it can be seen from fig. 2 that the larger lumps are anhydrous iron phosphate and the small particles are iron oxide.
The embodiment also discloses a preparation method of the lithium iron phosphate, which comprises the following steps:
s1, preparing materials
100g of anhydrous powder is taken out and transferred to a ball milling tank, 31.8g of battery-grade lithium phosphate, 13.89g of dextrose monohydrate, 582.76g of zirconium beads and 128.54g of deionized water are added, and the mixture is ball milled by a planetary ball mill until the mixture reaches d 50 And (3) spray drying the slurry at 180 ℃ to obtain a lithium iron phosphate precursor, wherein the particle size is 0.4 mu m.
S2, sintering
And (3) putting the lithium iron phosphate precursor into a tube furnace, introducing nitrogen, preserving heat for 6 hours at 750 ℃, naturally cooling, crushing by air flow, and sieving by a 300-mesh sieve to obtain a finished product of the lithium iron phosphate.
An SEM (scanning electron microscope) image (50000 times) of the lithium iron phosphate finished product prepared in this embodiment is shown in fig. 3, and it can be seen from fig. 3 that the number of the primary particle size of lithium iron phosphate is 100-.
Example 2
This example prepared an anhydrous iron phosphate and iron oxide mixture comprising the steps of:
s1, preparing a ferrous salt aqueous solution
500g of analytically pure iron sulfate heptahydrate and 0.5g of ascorbic acid are added to 600g of deionized water and dissolved at 35 ℃ with stirring at 420 rpm.
S2, preparing phosphate solution
158.3g of analytically pure diammonium phosphate and 0.8g of ethanol are added to 300g of deionized water and dissolved with stirring at 35 ℃.
S3, reaction
Transferring the phosphate solution into a spraying pot, spraying the phosphate solution into the iron liquid at a constant speed for 5 minutes, reacting for 20 minutes, adjusting the pH value of 10-20% ammonia water solution to 7.0 by using the spraying pot, reacting for 30 minutes, washing with deionized water, filtering until the filtrate is neutral, transferring to a ball milling tank, adding 1203g of zirconium beads and 240g of deionized water, ball milling by using a planetary ball mill until d50 is 0.3 mu m, and spray-drying the slurry at 180 ℃ to obtain powder.
S4, removing crystal water
And putting the powder into a tube furnace, introducing air, preserving heat for 3 hours at 300 ℃, then introducing oxygen, preserving heat for 3 hours at 620 ℃, and naturally cooling to obtain the anhydrous iron phosphate and ferric oxide mixture.
The embodiment also discloses a preparation method of the lithium iron phosphate, which comprises the following steps:
s1, preparing materials
And (3) taking out 100g of the anhydrous iron phosphate and iron oxide mixture, transferring the mixture into a ball milling tank, adding 31.8g of battery-grade lithium phosphate, 14.60g of dextrose monohydrate, 582.76g of zirconium beads and 128.54g of deionized water, ball milling the mixture by using a planetary ball mill until d50 is 0.3 mu m, and spray drying the slurry at 180 ℃ to obtain a lithium iron phosphate precursor.
S2, sintering
And (3) putting the lithium iron phosphate precursor into a tube furnace, introducing nitrogen, keeping the temperature at 820 ℃ for 8 hours, naturally cooling, crushing by air flow, and sieving by a 300-mesh sieve to obtain a finished product of the lithium iron phosphate.
As shown in fig. 4, an XRD pattern of the lithium iron phosphate finished product prepared in this embodiment can be seen from fig. 4 that the finished product is lithium iron phosphate and the crystallinity is 90%.
Finally, it should be noted that: the above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A method for solid phase synthesis of a mixture of anhydrous ferric phosphate and ferric oxide, the method comprising:
mixing a solution containing ferrous ions and a solution containing phosphate radical according to a molar ratio of 1.50 (0.95-1.05) for reaction to obtain a suspension;
separating the suspension to obtain a solid mixture, and then placing the solid mixture at the temperature of 180-300 ℃ for oxidizing and sintering to obtain the anhydrous ferric phosphate and ferric oxide mixture;
and carrying out second oxidation sintering at 550-650 ℃ after the oxidation sintering.
2. The method for solid-phase synthesis of the mixture of anhydrous iron phosphate and iron oxide according to claim 1, wherein the step of ball-milling the solid mixture to a particle size of 0.1-1.0 μm and drying at 180 ℃ is further included before the step of oxidizing and sintering the solid mixture at 300 ℃ under 180 ℃.
3. The method for solid phase synthesis of a mixture of anhydrous ferric phosphate and ferric oxide according to claim 1 or 2, wherein the ferrous ion is derived from at least one of ferrous sulfate, ferrous chloride and ferrous nitrate; preferably, the phosphate is derived from at least one of monoammonium phosphate, diammonium phosphate, triammonium phosphate or monosodium phosphate, disodium phosphate and trisodium phosphate.
4. The method for solid-phase synthesis of the mixture of anhydrous ferric phosphate and ferric oxide according to claim 1, wherein the suspension is separated to obtain a solid mixture, and then the solid mixture is subjected to oxidation sintering at 300 ℃ under 180 ℃ to obtain the mixture of anhydrous ferric phosphate and ferric oxide;
the oxidation sintering is carried out in the air;
preferably, the second oxidation sintering is carried out at 550-650 ℃ after the oxidation sintering;
the oxidative sintering is carried out in pure oxygen.
5. The method for solid-phase synthesis of the anhydrous iron phosphate and iron oxide mixture according to claim 1 or 2, wherein the solution containing ferrous ions and the solution containing phosphate are mixed and reacted according to a molar ratio of 1.50 (0.95-1.05) to obtain a suspension;
spraying the solution containing the phosphate radical into the solution containing the ferrous ions in a spraying mode.
6. A mixture of anhydrous iron phosphate and oxide prepared according to the method of any one of claims 1 to 5.
7. A preparation method of lithium iron phosphate is characterized by comprising the following steps:
mixing the anhydrous iron phosphate and iron oxide mixture according to any one of claims 1 to 5, lithium phosphate and a carbon-containing antioxidant, dissolving the mixture in a solvent to react, and drying the mixture to obtain a lithium iron phosphate precursor;
wherein: the mol ratio of the iron element, the lithium element, the phosphorus element and the carbon element is (0.97-1.00): (0.98-1.05):1.00 (0.52-0.65);
and (3) preserving the heat of the lithium iron phosphate precursor at the temperature of 700-850 ℃ in an oxygen-free environment to obtain the lithium iron phosphate.
8. The method of manufacturing according to claim 7, further comprising: grinding the lithium iron phosphate precursor until the particle size is more than 0.3 mu m and less than 0.5 mu m; preferably, the temperature during the drying is 120-180 ℃; preferably, the drying takes the form of a spray; preferably, in the lithium iron phosphate obtained by insulating the lithium iron phosphate precursor in an oxygen-free environment at 700-850 ℃, the steps of crushing and screening are also included after the heat insulation is completed; preferably, the pulverization adopts air flow pulverization; preferably, the screening is carried out by adopting 300-500-mesh screening.
9. Lithium iron phosphate prepared by the preparation method according to claim 7 or 8.
10. Use of the lithium iron phosphate of claim 9 in a battery material.
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