CN116654891A - Lithium iron phosphate precursor and preparation method and application thereof - Google Patents
Lithium iron phosphate precursor and preparation method and application thereof Download PDFInfo
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- CN116654891A CN116654891A CN202310670975.4A CN202310670975A CN116654891A CN 116654891 A CN116654891 A CN 116654891A CN 202310670975 A CN202310670975 A CN 202310670975A CN 116654891 A CN116654891 A CN 116654891A
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- iron phosphate
- lithium iron
- phosphate precursor
- reaction
- precursor
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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 90
- 239000002243 precursor Substances 0.000 title claims abstract description 63
- 238000002360 preparation method Methods 0.000 title claims abstract description 21
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims abstract description 61
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 47
- 238000006243 chemical reaction Methods 0.000 claims abstract description 33
- 239000005955 Ferric phosphate Substances 0.000 claims abstract description 31
- 229940032958 ferric phosphate Drugs 0.000 claims abstract description 31
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims abstract description 31
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 30
- 238000001354 calcination Methods 0.000 claims abstract description 25
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 15
- 238000004519 manufacturing process Methods 0.000 claims abstract description 14
- 239000012266 salt solution Substances 0.000 claims abstract description 10
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims abstract description 9
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 9
- 238000001035 drying Methods 0.000 claims abstract description 9
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 9
- 239000011259 mixed solution Substances 0.000 claims abstract description 9
- 239000007800 oxidant agent Substances 0.000 claims abstract description 8
- 230000001590 oxidative effect Effects 0.000 claims abstract description 6
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 42
- 238000000034 method Methods 0.000 claims description 25
- 239000007774 positive electrode material Substances 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 6
- 230000000630 rising effect Effects 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 11
- 239000002994 raw material Substances 0.000 abstract description 10
- 238000009776 industrial production Methods 0.000 abstract description 3
- 239000011790 ferrous sulphate Substances 0.000 description 51
- 235000003891 ferrous sulphate Nutrition 0.000 description 51
- 229910000359 iron(II) sulfate Inorganic materials 0.000 description 51
- 239000000243 solution Substances 0.000 description 44
- 239000013078 crystal Substances 0.000 description 43
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 30
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 29
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 26
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 description 22
- 238000005406 washing Methods 0.000 description 21
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 description 20
- 238000003756 stirring Methods 0.000 description 20
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 18
- 229910021389 graphene Inorganic materials 0.000 description 17
- 229910000398 iron phosphate Inorganic materials 0.000 description 17
- 230000000052 comparative effect Effects 0.000 description 14
- 239000001509 sodium citrate Substances 0.000 description 14
- NLJMYIDDQXHKNR-UHFFFAOYSA-K sodium citrate Chemical compound O.O.[Na+].[Na+].[Na+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O NLJMYIDDQXHKNR-UHFFFAOYSA-K 0.000 description 14
- 239000012535 impurity Substances 0.000 description 13
- 239000002002 slurry Substances 0.000 description 11
- 239000004408 titanium dioxide Substances 0.000 description 11
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 description 10
- 229910052799 carbon Inorganic materials 0.000 description 10
- 238000002156 mixing Methods 0.000 description 10
- 239000000047 product Substances 0.000 description 10
- 239000012065 filter cake Substances 0.000 description 9
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 8
- 238000001914 filtration Methods 0.000 description 8
- 239000012286 potassium permanganate Substances 0.000 description 8
- 239000000126 substance Substances 0.000 description 7
- 238000004448 titration Methods 0.000 description 7
- 239000006227 byproduct Substances 0.000 description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 6
- 239000000843 powder Substances 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 238000001694 spray drying Methods 0.000 description 5
- QAOWNCQODCNURD-UHFFFAOYSA-L Sulfate Chemical compound [O-]S([O-])(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-L 0.000 description 4
- 239000002253 acid Substances 0.000 description 4
- 239000010405 anode material Substances 0.000 description 4
- 239000002131 composite material Substances 0.000 description 4
- 239000005457 ice water Substances 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 229910052757 nitrogen Inorganic materials 0.000 description 4
- 230000035484 reaction time Effects 0.000 description 4
- 239000002699 waste material Substances 0.000 description 4
- 238000010668 complexation reaction Methods 0.000 description 3
- 238000001514 detection method Methods 0.000 description 3
- 239000000706 filtrate Substances 0.000 description 3
- 238000013508 migration Methods 0.000 description 3
- 230000005012 migration Effects 0.000 description 3
- 230000004048 modification Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 3
- -1 on one hand Chemical compound 0.000 description 3
- DPTATFGPDCLUTF-UHFFFAOYSA-N phosphanylidyneiron Chemical compound [Fe]#P DPTATFGPDCLUTF-UHFFFAOYSA-N 0.000 description 3
- 239000002244 precipitate Substances 0.000 description 3
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 description 3
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 2
- 108010009736 Protein Hydrolysates Proteins 0.000 description 2
- 238000002441 X-ray diffraction Methods 0.000 description 2
- 229910052782 aluminium Inorganic materials 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 238000006555 catalytic reaction Methods 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- CADNYOZXMIKYPR-UHFFFAOYSA-B ferric pyrophosphate Chemical compound [Fe+3].[Fe+3].[Fe+3].[Fe+3].[O-]P([O-])(=O)OP([O-])([O-])=O.[O-]P([O-])(=O)OP([O-])([O-])=O.[O-]P([O-])(=O)OP([O-])([O-])=O CADNYOZXMIKYPR-UHFFFAOYSA-B 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 229910052744 lithium Inorganic materials 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 229910052596 spinel Inorganic materials 0.000 description 2
- 239000011029 spinel Substances 0.000 description 2
- 239000000725 suspension Substances 0.000 description 2
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 1
- 229910010707 LiFePO 4 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
- 239000002033 PVDF binder Substances 0.000 description 1
- 229930006000 Sucrose Natural products 0.000 description 1
- 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 description 1
- 229910010413 TiO 2 Inorganic materials 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 239000007864 aqueous solution Substances 0.000 description 1
- 239000012298 atmosphere Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011449 brick Substances 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 150000001860 citric acid derivatives Chemical class 0.000 description 1
- 239000000470 constituent Substances 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 230000018044 dehydration Effects 0.000 description 1
- 238000006297 dehydration reaction Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- 239000004744 fabric Substances 0.000 description 1
- 230000002349 favourable effect Effects 0.000 description 1
- 239000011706 ferric diphosphate Substances 0.000 description 1
- 235000007144 ferric diphosphate Nutrition 0.000 description 1
- 229960004887 ferric hydroxide Drugs 0.000 description 1
- 229940036404 ferric pyrophosphate Drugs 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000000413 hydrolysate Substances 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 description 1
- BMTOKWDUYJKSCN-UHFFFAOYSA-K iron(3+);phosphate;dihydrate Chemical compound O.O.[Fe+3].[O-]P([O-])([O-])=O BMTOKWDUYJKSCN-UHFFFAOYSA-K 0.000 description 1
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 1
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 1
- 229910052808 lithium carbonate Inorganic materials 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 238000004321 preservation Methods 0.000 description 1
- 238000004080 punching Methods 0.000 description 1
- 238000000197 pyrolysis Methods 0.000 description 1
- 238000005215 recombination Methods 0.000 description 1
- 230000006798 recombination Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 238000005096 rolling process Methods 0.000 description 1
- 238000007873 sieving Methods 0.000 description 1
- 239000011734 sodium Substances 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 239000005720 sucrose Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000005979 thermal decomposition reaction Methods 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
Classifications
-
- 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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- 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
-
- 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
-
- 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
- C01P2006/80—Compositional purity
-
- 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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- 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 relates to the field of lithium ion battery material preparation, in particular to a lithium iron phosphate precursor, a preparation method and application thereof. The preparation method of the lithium iron phosphate precursor comprises the following steps: adding an oxidant into the mixed solution of phosphoric acid and a ferrous salt solution to perform a first reaction to obtain a first mixed system; adjusting the pH value of the first mixed system to 0.5-3, and then carrying out a second reaction to obtain ferric phosphate dihydrate; and drying and calcining the mixed solution containing the ferric phosphate dihydrate and the citrate to obtain the lithium iron phosphate precursor. The preparation method of the lithium iron phosphate precursor has the advantages of wide raw material sources, low price, short production process period and easiness in operation, and the prepared precursor can improve the conductivity of the lithium iron phosphate product and is suitable for large-scale industrial production and application.
Description
Technical Field
The invention relates to the field of lithium ion battery material preparation, in particular to a lithium iron phosphate precursor, a preparation method and application thereof.
Background
The lithium iron phosphate anode material is the lithium battery anode material which is most rapidly developed in China at present, has wide raw material sources and low price, and is widely applied to the fields of automobiles, electric tools, energy storage equipment, mobile power supplies and the like in the domestic battery industry. Compared with other anode materials, the lithium iron phosphate has the advantages of safety, environmental protection, low cost, long cycle life, good high-temperature performance and the like, and is one of the anode materials of the lithium ion battery with the highest potential. The pure-phase lithium iron phosphate has lower electronic conductivity, so that the charge-discharge efficiency and the discharge specific capacity of the pure-phase lithium iron phosphate are lower, and particularly the rate capability is poorer, thereby greatly limiting the wide application of the lithium iron phosphate.
In view of this, the present invention has been made.
Disclosure of Invention
One aspect of the invention relates to a method for preparing a lithium iron phosphate precursor, comprising the following steps:
adding an oxidant into the mixed solution of phosphoric acid and a ferrous salt solution to perform a first reaction to obtain a first mixed system; adjusting the pH value of the first mixed system to 0.5-3, and then carrying out a second reaction to obtain ferric phosphate dihydrate;
and drying and calcining the mixed solution containing the ferric phosphate dihydrate and the citrate to obtain the lithium iron phosphate precursor.
The preparation method of the lithium iron phosphate precursor has the advantages of wide raw material sources, low price, short production process period and easiness in operation, and the prepared precursor can improve the conductivity of the lithium iron phosphate product and is suitable for large-scale industrial production and application.
The invention also relates to the lithium iron phosphate precursor prepared by the preparation method of the lithium iron phosphate precursor;
preferably, the particle size of the lithium iron phosphate precursor is 1.0-2.5 μm.
The lithium iron phosphate precursor can improve the conductivity of lithium iron phosphate, and has wide sources of production raw materials and low cost.
In another aspect, the invention also relates to a lithium iron phosphate, which is mainly prepared from the lithium iron phosphate precursor.
The lithium iron phosphate has low impurity content, good conductivity and excellent electrochemical performance.
In another aspect, the invention also relates to a positive electrode material comprising the lithium iron phosphate.
In another aspect, the invention also relates to a lithium ion battery, which comprises the positive electrode material.
Compared with the prior art, the invention has the beneficial effects that:
(1) According to the preparation method of the lithium iron phosphate precursor, sodium citrate is used as a carbon source, the graphene structure is prepared under the conditions of iron catalytic reaction and high-temperature pyrolysis, so that the in-situ recombination of graphene on the surface of the iron phosphate is realized, the conductivity of a lithium iron phosphate product is further improved, the source of raw materials is wide, the price is low, the production process period is short, and the preparation method is easy to operate and suitable for large-scale industrial production and application.
(2) The lithium iron phosphate precursor provided by the invention has low impurity content, can improve the conductivity of lithium iron phosphate, and has wide sources of production raw materials and low production cost.
(3) The lithium iron phosphate provided by the invention has the advantages of low impurity content, good conductivity, high charge and discharge capacity of the material, better multiplying power performance and excellent electrochemical performance, and is favorable for lithium ion migration.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
FIG. 1 is an XRD pattern of the lithium iron phosphate precursor of example 1;
fig. 2 is an XRD pattern of lithium iron phosphate prepared from the lithium iron phosphate precursor of example 1.
Detailed Description
The technical solution of the present invention will be clearly and completely described below with reference to the accompanying drawings and detailed description, but it will be understood by those skilled in the art that the examples described below are some, but not all, examples of the present invention, and are intended to be illustrative of the present invention only and should not be construed as limiting the scope of the present invention. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention. The specific conditions are not noted in the examples and are carried out according to conventional conditions or conditions recommended by the manufacturer. The reagents or apparatus used were conventional products commercially available without the manufacturer's attention.
One aspect of the invention relates to a method for preparing a lithium iron phosphate precursor, comprising the following steps:
adding an oxidant into the mixed solution of phosphoric acid and a ferrous salt solution to perform a first reaction to obtain a first mixed system; adjusting the pH of the first mixed system to 0.5-3 (such as 0.5, 1, 1.5, 2, 2.5 or 3), and then performing a second reaction to obtain ferric phosphate dihydrate;
and drying and calcining the mixed solution containing the ferric phosphate dihydrate and the citrate to obtain the lithium iron phosphate precursor.
Graphene, as an advanced carbon material, is considered as an ideal component of a composite electrode material due to its superior electron conductivity, large specific surface area, and special two-dimensional structure. Lithium iron phosphate is used as a positive electrode material, and Li is removed and intercalated between two phases of the lithium iron phosphate and the lithium iron phosphate in the charge and discharge process + And the ferric phosphate is used as a precursor of lithium iron phosphate, and the crystal structure is not changed in the charging and discharging process. The invention designs the three-dimensional FePO with special morphology and microstructure by using the graphene as the constituent unit 4 The graphene composite material is used as a lithium iron phosphate precursor, sodium citrate is used as a graphene raw material, the sodium citrate is dissolved in ferric phosphate dihydrate slurry, so that the sodium citrate and the ferric phosphate are uniformly mixed, and are better combined with iron phosphate through complexation of iron, and citric acid is decomposed at high temperature to form a graphene structure under the catalysis of iron and is uniformly combined with the iron phosphate, so that the graphene is directly compounded into a spinel structure of lithium iron phosphate, and Li is better promoted + Has promotion effect on improving the conductivity of lithium iron phosphate products.
According to the invention, sodium citrate is selected as a carbon source for preparing graphene, on one hand, citrate and Fe have complexation, sodium citrate is dissolved in ferric phosphate dihydrate slurry, so that the citrate and the ferric phosphate are uniformly mixed, and the graphene structure formed by citric acid decomposition is uniformly compounded into the spinel structure of the ferric phosphate through the complexation of the iron, so that the ferric phosphate has more lithium ion migration channels, the lithium ion migration rate is accelerated, and the charge and discharge performance of the material is improved; on the other hand, sodium citrate is easier to form a graphene structure under the Fe catalytic condition and under the thermal decomposition condition, so that the reaction calcination temperature is reduced, the crystal form conversion of anhydrous ferric phosphate formed by dehydration of ferric phosphate dihydrate is not influenced while the graphene structure is formed, and the ferric phosphate is prevented from forming ferric pyrophosphate heterogeneous phase due to overhigh temperature.
Preferably, the molar ratio of the Fe element in the ferrous salt solution to the P element in the phosphoric acid is 1: 1-3 (e.g., 1:1, 1:1.5, 1:2, 1:2.5, or 1:3).
Preferably, the molar ratio of the Fe element in the ferrous salt solution to the oxidizing agent is 1: 1-2 (e.g., 1:1, 1:1.2, 1:1.4, 1:1.6, 1:1.8, or 1:2). The molar ratio of Fe element and oxidant in the ferrous salt solution is controlled within a certain range, so that ferrous iron is fully converted into ferric iron.
Preferably, the oxidizing agent comprises hydrogen peroxide.
Preferably, the mass concentration of the hydrogen peroxide is 20-27.5%.
Preferably, the mass ratio of the ferric phosphate dihydrate to the citrate is 1: (0.3-1) (e.g., 1:0.3, 1:0.4, 1:0.5, 1:0.6, 1:0.7, 1:0.8, 1:0.9, or 1:1).
Preferably, the temperature of the first reaction is 60 to 105 ℃ (e.g., 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, or 105 ℃).
Preferably, the time of the first reaction is 2 to 6 hours (e.g., 2 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, 5 hours, or 6 hours).
Preferably, the temperature of the second reaction is 60 to 105 ℃ (e.g., 60 ℃, 65 ℃, 70 ℃, 75 ℃, 80 ℃, 85 ℃, 90 ℃, 95 ℃, 100 ℃, or 105 ℃).
Preferably, the second reaction is carried out for a period of time ranging from 0.5 to 5 hours (e.g., 0.5 hours, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, 3.5 hours, 4 hours, 4.5 hours, or 5 hours).
The temperature of the first reaction and the second reaction is controlled within a certain range, so that the reaction is ensured to be fully carried out, and the material consumption is reduced.
Preferably, the calcination temperature is 600 to 1000 ℃ (e.g., 600 ℃, 630 ℃, 660 ℃, 690 ℃, 720 ℃, 750 ℃, 780 ℃, 810 ℃, 840 ℃, 870 ℃, 900 ℃, 930 ℃, 960 ℃, 990 ℃, or 1000 ℃).
Preferably, the calcination is for a period of time ranging from 1 to 10 hours (e.g., 1 hour, 3 hours, 5 hours, 7 hours, 9 hours, or 10 hours).
Preferably, the temperature rise rate of the calcination is 4 to 30 ℃/min (e.g., 4 ℃/min, 8 ℃/min, 12 ℃/min, 16 ℃/min, 20 ℃/min, 24 ℃/min, 28 ℃/min, or 30 ℃/min).
Preferably, the calcination is performed under the protection of inert gas.
The ferrous salt solution adopted by the invention can be prepared from ferrous sulfate crystal which is a byproduct in the production process of titanium dioxide by a sulfuric acid method, and the specific preparation method comprises the following steps:
1. dissolving ferrous sulfate crystals which are byproducts in the production process of titanium dioxide by a sulfuric acid method in pure water at 40-80 ℃, fully dissolving under stirring conditions, and obtaining a semitransparent ferrous sulfate solution A after the solution is semitransparent after dissolving, wherein the solution is in a milky suspended substance which is a hydrated titanium dioxide of an oxytitanium sulfate hydrolysate; sulfuric acid is added to ensure that the pH value of the solution is=0.5-1.0, thereby avoiding long-time high-temperature Fe 2+ Oxidation to Fe 3+ pH is greater than 1.0, fe 2+ Is easy to oxidize, has pH less than 0.5, can cause sulfuric acid waste, ensures the system to have enough acidity, and avoids Fe 2+ Oxidizing; the mass concentration of sulfuric acid is 8-98%, the concentration of ferrous sulfate is 90-160 g/L, and the concentration of solution is Fe 2+ Titration is carried out by a potassium permanganate method, and the concentration of ferrous sulfate is determined;
2. putting the solution A into ice water, slightly stirring until light green ferrous sulfate crystals appear, stopping stirring, standing to enable the solution to be completely crystallized, and filtering the crystals to obtain ferrous sulfate crystals B; placing the mixture into ice water for slight stirring, avoiding the excessive stirring speed to ensure that crystals are not easy to separate out, ensuring that the crystals which are not stirred to separate out are excessively large, ensuring that part of impurities are mixed into the crystals and are not easy to wash out the impurities, stopping stirring after obvious crystals separate out, ensuring that ferrous sulfate slowly grows on the separated crystal nucleus, facilitating the next water washing, and simultaneously avoiding impurities from being mixed into the crystals;
3. washing the above crystal B with analytically pure ethanol solution until the filtrate is clear and no white suspended matter (TiO) is present 2 Washing out, and taking out the crystal to obtain a pure blue-green ferrous sulfate crystal C for later use;
4. dissolving ferrous sulfate crystal C in water to obtain solution with concentration of 40-100g/L, and Fe 2+ And (3) titrating by a potassium permanganate method to determine the concentration of ferrous sulfate.
The invention uses ferrous sulfate crystals as a byproduct in the production process of titanium dioxide by a sulfuric acid method as a raw material, utilizes the titanium dioxide by the sulfuric acid method, has simple raw material source and low cost, and simultaneously solves the problem of stacking the ferrous sulfate crystals as waste side products of titanium dioxide by the sulfuric acid method.
The invention recrystallizes the waste paraferrous sulfate crystal to remove redundant impurities, and simultaneously washes the ferrous sulfate crystal by ethanol to reduce the impurity TiO 2 The content of the ferrous sulfate crystals is avoided, the ferrous sulfate utilization rate is improved, and the pure ferrous sulfate crystals are obtained, so that the impurity of the prepared ferric phosphate is reduced.
Preferably, the mass concentration of the phosphoric acid is 75% -85%, and the mass concentration is 85% in summer and 75% in winter.
Preferably, the pH value of the first mixed system is regulated by adopting sodium hydroxide solution, and the mass concentration of the sodium hydroxide solution is 5-12%. Too high a concentration of Fe 3+ The brick red ferric hydroxide precipitate is easy to form, the concentration is too low, the particle size of the formed precipitate particles is too small, the precipitate is filtered from the filtering device, waste is caused, and meanwhile, the filter cloth is blocked by too small particles, so that the washing is not facilitated.
Preferably, the solid content of the mixed solution containing the ferric phosphate dihydrate and the citrate is 5-15%. Thereby ensuring that the ferric phosphate can be better dispersed in the aqueous solution, and the sodium citrate can be fully combined with the ferric phosphate to form in-situ coating.
Preferably, the citrate salt comprises sodium citrate.
The invention also relates to the lithium iron phosphate precursor prepared by the preparation method of the lithium iron phosphate precursor;
preferably, the particle size of the lithium iron phosphate precursor is 1.0-2.5 μm.
The lithium iron phosphate precursor can improve the conductivity of lithium iron phosphate, and has wide sources of production raw materials and low cost.
In another aspect, the invention also relates to a lithium iron phosphate, which is mainly prepared from the lithium iron phosphate precursor.
The lithium iron phosphate has low impurity content, good conductivity and excellent electrochemical performance.
In another aspect, the invention also relates to a positive electrode material comprising the lithium iron phosphate.
In another aspect, the invention also relates to a lithium ion battery, which comprises the positive electrode material.
Embodiments of the present invention will be described in detail below with reference to specific examples and comparative examples.
Example 1
The preparation method of the lithium iron phosphate precursor provided by the embodiment comprises the following steps:
1. dissolving ferrous sulfate crystals which are byproducts in the production process of titanium dioxide by a sulfuric acid method in pure water at 60 ℃, fully dissolving under the stirring condition, and obtaining a semitransparent ferrous sulfate solution A after the solution is in a semitransparent state, wherein the solution is in a milky suspended substance, the suspended substance is a hydrated titanium dioxide which is an oxytitanium sulfate hydrolysate, and insoluble substances in the suspension are filtered to obtain the semitransparent ferrous sulfate solution A; adding 98% sulfuric acid to make pH=0.8, ferrous sulfate concentration 120g/L, solution concentration Fe 2+ Titration is carried out by a potassium permanganate method, and the concentration of ferrous sulfate is determined;
2. placing the ferrous sulfate solution A into ice water, slightly stirring until light green and fine ferrous sulfate crystals appear, stopping stirring, standing, completely crystallizing the solution, and filtering the crystals to obtain yellow green ferrous sulfate crystals B;
3. washing the ferrous sulfate crystal B with analytically pure ethanol solution until the filtrate is clear and no white suspended matter (TiO) is present 2 Washing out, and taking out the crystal to obtain a pure blue-green ferrous sulfate crystal C for later use;
4. dissolving ferrous sulfate crystal C in water to obtain 85g/L solution with Fe concentration 2+ Titration is carried out by a potassium permanganate method, and the concentration of ferrous sulfate is determined; according to Fe: p=1: 1.5 (molar ratio) phosphoric acid was slowly added to the ferrous sulfate solution in terms of molar ratio Fe: h 2 O 2 Hydrogen peroxide is added to carry out a first reaction in a ratio of 1:1.5 to obtain a first mixed systemThe first reaction temperature is 60 ℃, the first reaction time is 4 hours, sodium hydroxide is added to adjust the pH value of the first mixed system to 2.0 for carrying out the second reaction, stirring is carried out for 1 hour under the condition of heat preservation and 95 ℃, and then the powder white ferric phosphate dihydrate filter cake D is obtained by filtering and washing; phosphoric acid concentration 75%; the concentration of hydrogen peroxide is 25%; sodium hydroxide concentration 8%;
5. mixing the iron phosphate filter cake D with water to prepare slurry with the solid content of 10%, adding sodium citrate with the mass 1 time of that of the iron phosphate as a grapheme carbon source, stirring and mixing uniformly, and then spray-drying to obtain a precursor E;
6. calcining the precursor E under the protection of nitrogen, wherein the calcining temperature is 750 ℃, the calcining time is 9 hours, and the calcined product is subjected to acid washing, water washing and drying to obtain the lithium iron phosphate precursor.
Example 2
The preparation method of the lithium iron phosphate precursor provided by the embodiment comprises the following steps:
1. dissolving ferrous sulfate crystals which are byproducts in the production process of titanium dioxide by a sulfuric acid method in pure water at 60 ℃, fully dissolving under the stirring condition, and obtaining a semitransparent ferrous sulfate solution A after the solution is in a semitransparent state, wherein the solution is in a milky suspended substance, the suspended substance is a hydrated titanium dioxide which is an oxytitanium sulfate hydrolysate, and insoluble substances in the suspension are filtered to obtain the semitransparent ferrous sulfate solution A; note that sulfuric acid was added to give a solution ph=1.0 with a ferrous sulfate concentration of 100g/L, the solution concentration being Fe 2+ Titration is carried out by a potassium permanganate method, and the concentration of ferrous sulfate is determined;
2. placing the ferrous sulfate solution A into ice water, slightly stirring until light green and fine ferrous sulfate crystals appear, stopping stirring, standing to completely crystallize the solution, and filtering the crystals to obtain ferrous sulfate crystals B;
3. washing the ferrous sulfate crystal B with analytically pure ethanol solution until the filtrate is clear and no white suspended matter (TiO) is present 2 Washing out, and taking out the crystal to obtain a pure blue-green ferrous sulfate crystal C for later use;
4. dissolving ferrous sulfate crystal C in water to obtain solution with solution concentration of 60g/L, and the solution concentration is Fe 2+ Titration is carried out by potassium permanganate method, and the ferrous sulfate concentration is determinedA degree; according to Fe: p=1: 1.5 Phosphoric acid was slowly added to the ferrous sulfate solution according to Fe: h 2 O 2 =1: 1.2 Adding hydrogen peroxide (molar ratio) to perform a first reaction to obtain a first mixed system, wherein the first reaction temperature is 60 ℃, the first reaction time is 4 hours, adding sodium hydroxide to adjust the pH value of the first mixed system to 1.6 to perform a second reaction, stirring for 2 hours at the temperature of 97 ℃, and filtering and washing to obtain a white powder ferric phosphate filter cake D; phosphoric acid concentration 75%; the concentration of hydrogen peroxide is 25%; sodium hydroxide concentration 10%;
5. mixing the iron phosphate filter cake D with water to prepare slurry with the solid content of 15%, adding sodium citrate with the mass of 0.5 times of that of the iron phosphate as a grapheme carbon source, stirring and mixing uniformly, and then spray-drying to obtain a precursor E;
6. calcining the precursor E under the protection of nitrogen, wherein the calcining temperature is 795 ℃, the calcining time is 7 hours, and the calcined product is subjected to acid washing, water washing and drying to obtain the lithium iron phosphate precursor.
Example 3
The preparation method of the lithium iron phosphate precursor provided by the embodiment comprises the following steps:
1-3. The same as in example 1;
4. dissolving ferrous sulfate crystal C in water to obtain 85g/L solution with Fe concentration 2+ Titration is carried out by a potassium permanganate method, and the concentration of ferrous sulfate is determined; according to Fe: p=1: 1 (molar ratio) phosphoric acid is slowly added into ferrous sulfate solution according to the molar ratio of Fe: h 2 O 2 Adding hydrogen peroxide into the mixture in a ratio of 1:1 to perform a first reaction to obtain a first mixed system, wherein the first reaction temperature is 105 ℃, the first reaction time is 3 hours, adding sodium hydroxide to adjust the pH value of the first mixed system to 2.0 to perform a second reaction, stirring the mixture for 0.5 hours at the temperature of 105 ℃, and filtering and washing the mixture to obtain a white powder ferric phosphate filter cake D; phosphoric acid concentration 75%; the concentration of hydrogen peroxide is 25%; sodium hydroxide concentration 8%;
5. mixing the iron phosphate filter cake D with water to prepare slurry with the solid content of 10%, adding sodium citrate with the mass of 0.3 times of that of the iron phosphate as a grapheme carbon source, stirring and mixing uniformly, and then spray-drying to obtain a precursor E;
6. calcining the precursor E under the protection of nitrogen, wherein the calcining temperature is 1000 ℃, the calcining time is 1h, and the calcined product is subjected to acid washing, water washing and drying to obtain the lithium iron phosphate precursor.
Example 4
The preparation method of the lithium iron phosphate precursor provided by the embodiment comprises the following steps:
1-3. The same as in example 1;
4. dissolving ferrous sulfate crystal C in water to obtain 85g/L solution with Fe concentration 2+ Titration is carried out by a potassium permanganate method, and the concentration of ferrous sulfate is determined; according to Fe: p=1: 3 (molar ratio) phosphoric acid is slowly added into ferrous sulfate solution according to the molar ratio of Fe: h 2 O 2 Adding hydrogen peroxide to perform a first reaction to obtain a first mixed system, wherein the first reaction temperature is 75 ℃, the first reaction time is 5 hours, adding sodium hydroxide to adjust the pH of the first mixed system to 2.0 to perform a second reaction, stirring for 5 hours at the temperature of 60 ℃, and filtering and washing to obtain a white powder ferric phosphate filter cake D; phosphoric acid concentration 75%; the concentration of hydrogen peroxide is 25%; sodium hydroxide concentration 8%;
5. mixing the iron phosphate filter cake D with water to prepare slurry with the solid content of 10%, adding sodium citrate with the mass of 0.6 times of that of the iron phosphate as a grapheme carbon source, stirring and mixing uniformly, and then spray-drying to obtain a precursor E;
6. calcining the precursor E under the protection of nitrogen, wherein the calcining temperature is 600 ℃, the calcining time is 10 hours, and the calcined product is subjected to acid washing, water washing and drying to obtain the lithium iron phosphate precursor.
Comparative example 1
This comparative example differs from example 1 in that in step 4, the pH of the first mixed system is adjusted to 3.5.
Comparative example 2
The difference between this comparative example and example 1 is step 5, step 5 being specifically: and carrying out flash evaporation drying on the iron phosphate filter cake D to obtain the iron phosphate dihydrate powder E.
Experimental example 1
ICP full-component detection is carried out on the lithium iron phosphate precursors prepared in each example and comparative example, fe/P is calculated, carbon content is measured, and detection results are shown in table 1.
TABLE 1 index detection results of lithium iron phosphate precursor
| Index (I) | Example 1 | Example 2 | Example 3 | Example 4 | Comparative example 1 | Comparative example 2 |
| Fe％ | 36.39 | 36.29 | 35.85 | 36.62 | 35.37 | 36.37 |
| P％ | 20.89 | 20.89 | 20.88 | 20.94 | 20.55 | 20.9 |
| Fe/P | 0.966 | 0.963 | 0.953 | 0.969 | 0.956 | 0.965 |
| Carbon content% | 3.96 | 1.35 | 1.12 | 2.08 | 3.89 | 0.05 |
| Al(ppm) | 11 | 7 | 8 | 13 | 183 | 13 |
| Ca(ppm) | 0 | 14 | 5 | 4 | 95 | 9 |
| Cd(ppm) | 0 | 0 | 0 | 0 | 0 | 0 |
| Co(ppm) | 1 | 1 | 1 | 0 | 0 | 0 |
| Cr(ppm) | 5 | 4 | 6 | 4 | 3 | 3 |
| Cu(ppm) | 3 | 3 | 4 | 2 | 1 | 1 |
| K(ppm) | 38 | 30 | 23 | 28 | 34 | 34 |
| Mg(ppm) | 15 | 12 | 15 | 11 | 56 | 16 |
| Mn(ppm) | 42 | 32 | 22 | 26 | 108 | 53 |
| Na(ppm) | 132 | 85 | 30 | 94 | 111 | 40 |
| Ni(ppm) | 0 | 0 | 0 | 0 | 0 | 0 |
| Ti(ppm) | 1 | 1 | 0 | 2 | 3 | 2 |
As can be seen from Table 1, the preparation method of the lithium iron phosphate precursor provided by the invention can reduce the impurity content in the ferric phosphate by recrystallizing ferrous sulfate crystals in the production process of titanium dioxide by a sulfuric acid method and washing the ferrous sulfate crystals by an ethanol solution; the carbon content of the iron phosphate graphene compound can be adjusted by adjusting the addition amount of sodium citrate, the iron-phosphorus ratio in comparative example 1 is reduced, and the impurity content such as Al, ca, mg, mn is increased; example 3 iron pyrophosphate formed due to the too high calcination temperature, iron phosphorus was relatively low; in comparative example 2, the carbon content of graphene is only 0.5%, and the iron-phosphorus ratio of the prepared iron phosphate product is not changed obviously after graphene is added.
Experimental example 2
Lithium iron phosphate precursors obtained in examples and comparative examples were respectively prepared into lithium iron phosphate, and then lithium iron phosphate was respectively prepared into button cells.
Preparing lithium iron phosphate: adding the dried ferric phosphate and graphene compound or ferric phosphate (Fe PO 4) solid and lithium carbonate into a ball milling tank according to the proportion of Li: fe=1.015:1 (the comparative example 2 also needs to be added with sucrose with the molar quantity of Fe being 10%), mixing, pouring water to prepare 40% solution, and ball milling for 4 hours through a planetary ball mill. Taking out the slurry, spray drying, roasting for 9 hours at 750 ℃ in a nitrogen atmosphere of a tube furnace, and performing carbothermic reduction to obtain LiFePO 4 And (3) crushing graphene, and sieving by a 100-mesh sieve to obtain a product.
Preparation of button cell: mixing PVDF, acetylene black and LiFePO4 powder in a mass ratio of 1:1:8, adding N-methyl pyrrolidone to prepare slurry, uniformly coating the slurry on an aluminum foil, taking out the slurry after vacuum drying, rolling and punching the slurry into a round electrode plate with the diameter of 12 mm. The coin cell was assembled in a glove box (high purity Ar atmosphere), and the electrolyte included: 1mol/L LiPF6, a volume ratio of DCM, EC, EMC is 1:1:1, a metal lithium sheet is adopted as a negative electrode, and a Celgard film is adopted as a diaphragm. The constant current charge-discharge cycle test of the button cell shows that the charge-discharge voltage is 2.5-4.2V. The results are shown in Table 2.
TABLE 2 electrochemical performance test results of lithium iron phosphate
As can be seen from table 2, after graphene materials with different proportions are added in the embodiment of the present invention, discharge capacities of 0.1C, 0.2C, 0.33C, 0.5C, 1C, 2C, and 5C are different, and rate capability of the lithium iron phosphate positive electrode material prepared by using the lithium iron phosphate precursor of embodiment 1 is better than that of embodiment 2 and embodiment 3; meanwhile, after graphene is added in the examples 1-4 to prepare the iron phosphate-graphene composite material, the multiplying power performance of the continuously prepared lithium iron phosphate material is superior to that of the lithium iron phosphate material prepared by the iron phosphate without graphene in the comparative example 2; whereas comparative example 1 had poor electrical properties due to higher impurity content.
Fig. 1 shows a complete comparison of the iron phosphate-graphene composite material prepared by the invention with an iron phosphate standard card, illustrating that a pure-phase iron phosphate material is prepared.
As can be seen from fig. 2, the lithium iron phosphate material prepared from the lithium iron phosphate precursor of the present invention is completely compared with the standard card of lithium iron phosphate, and the prepared lithium iron phosphate material is pure-phase lithium iron phosphate.
While the invention has been illustrated and described with reference to specific embodiments, it is to be understood that the above embodiments are merely illustrative of the technical aspects of the invention and not restrictive thereof; those of ordinary skill in the art will appreciate that: modifications may be made to the technical solutions described in the foregoing embodiments, or equivalents may be substituted for some or all of the technical features thereof, without departing from the spirit and scope of the present invention; such modifications and substitutions do not depart from the spirit of the corresponding technical solutions; it is therefore intended to cover in the appended claims all such alternatives and modifications as fall within the scope of the invention.
Claims (10)
1. The preparation method of the lithium iron phosphate precursor is characterized by comprising the following steps of:
adding an oxidant into the mixed solution of phosphoric acid and a ferrous salt solution to perform a first reaction to obtain a first mixed system; adjusting the pH value of the first mixed system to 0.5-3, and then carrying out a second reaction to obtain ferric phosphate dihydrate;
and drying and calcining the mixed solution containing the ferric phosphate dihydrate and the citrate to obtain the lithium iron phosphate precursor.
2. The method for producing a lithium iron phosphate precursor according to claim 1, wherein a molar ratio of Fe element in the ferrous salt solution to P element in the phosphoric acid is 1:1 to 3;
preferably, the molar ratio of the Fe element in the ferrous salt solution to the oxidizing agent is 1:1 to 2.
3. The method for preparing a lithium iron phosphate precursor according to claim 1, wherein the mass ratio of the ferric phosphate dihydrate to the citrate is 1: (0.3-1).
4. The method for preparing a lithium iron phosphate precursor according to claim 1, wherein the temperature of the first reaction is 60 to 105 ℃;
preferably, the time of the first reaction is 2 to 6 hours.
5. The method for preparing a lithium iron phosphate precursor according to claim 1, wherein the temperature of the second reaction is 60 to 105 ℃;
preferably, the time of the second reaction is 0.5 to 5 hours.
6. The method for preparing a lithium iron phosphate precursor according to claim 1, wherein the calcining temperature is 600 to 1000 ℃;
preferably, the calcination time is 1 to 10 hours;
preferably, the temperature rising rate of the calcination is 4-30 ℃/min.
7. A lithium iron phosphate precursor prepared by the method for preparing a lithium iron phosphate precursor according to any one of claims 1 to 6;
preferably, the particle size of the lithium iron phosphate precursor is 1.0-2.5 μm.
8. A lithium iron phosphate made essentially of the lithium iron phosphate precursor of claim 7.
9. A positive electrode material comprising the lithium iron phosphate of claim 8.
10. A lithium ion battery comprising the positive electrode material of claim 9.
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