CN114835101A - Composition for preparing lithium iron phosphate, preparation method of lithium iron phosphate and battery anode material - Google Patents
Composition for preparing lithium iron phosphate, preparation method of lithium iron phosphate and battery anode material Download PDFInfo
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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 177
- 238000002360 preparation method Methods 0.000 title claims abstract description 40
- 239000000203 mixture Substances 0.000 title claims abstract description 29
- 239000010405 anode material Substances 0.000 title abstract description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 48
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 48
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims abstract description 27
- 229910052808 lithium carbonate Inorganic materials 0.000 claims abstract description 27
- 239000005955 Ferric phosphate Substances 0.000 claims abstract description 23
- 229940032958 ferric phosphate Drugs 0.000 claims abstract description 23
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims abstract description 23
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical group [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 22
- YNQRWVCLAIUHHI-UHFFFAOYSA-L dilithium;oxalate Chemical compound [Li+].[Li+].[O-]C(=O)C([O-])=O YNQRWVCLAIUHHI-UHFFFAOYSA-L 0.000 claims abstract description 9
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 53
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 51
- 229910052799 carbon Inorganic materials 0.000 claims description 51
- 238000000034 method Methods 0.000 claims description 45
- 238000005245 sintering Methods 0.000 claims description 33
- 239000011164 primary particle Substances 0.000 claims description 27
- 229910052742 iron Inorganic materials 0.000 claims description 26
- 238000007599 discharging Methods 0.000 claims description 25
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 24
- 230000008569 process Effects 0.000 claims description 19
- -1 ethoxy compound Chemical class 0.000 claims description 16
- BMTOKWDUYJKSCN-UHFFFAOYSA-K iron(3+);phosphate;dihydrate Chemical compound O.O.[Fe+3].[O-]P([O-])([O-])=O BMTOKWDUYJKSCN-UHFFFAOYSA-K 0.000 claims description 13
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052698 phosphorus Inorganic materials 0.000 claims description 12
- 239000011574 phosphorus Substances 0.000 claims description 12
- VBICKXHEKHSIBG-UHFFFAOYSA-N 1-monostearoylglycerol Chemical compound CCCCCCCCCCCCCCCCCC(=O)OCC(O)CO VBICKXHEKHSIBG-UHFFFAOYSA-N 0.000 claims description 10
- PYSRRFNXTXNWCD-UHFFFAOYSA-N 3-(2-phenylethenyl)furan-2,5-dione Chemical compound O=C1OC(=O)C(C=CC=2C=CC=CC=2)=C1 PYSRRFNXTXNWCD-UHFFFAOYSA-N 0.000 claims description 7
- 229920000147 Styrene maleic anhydride Polymers 0.000 claims description 7
- DPTATFGPDCLUTF-UHFFFAOYSA-N phosphanylidyneiron Chemical compound [Fe]#P DPTATFGPDCLUTF-UHFFFAOYSA-N 0.000 claims description 7
- 239000007774 positive electrode material Substances 0.000 claims description 7
- 239000011347 resin Substances 0.000 claims description 7
- 229920005989 resin Polymers 0.000 claims description 7
- 238000002156 mixing Methods 0.000 abstract description 53
- 239000000463 material Substances 0.000 abstract description 30
- 238000007580 dry-mixing Methods 0.000 abstract description 12
- 239000002245 particle Substances 0.000 description 20
- 238000000576 coating method Methods 0.000 description 19
- 239000002243 precursor Substances 0.000 description 18
- 239000002994 raw material Substances 0.000 description 17
- 238000012360 testing method Methods 0.000 description 16
- 239000011248 coating agent Substances 0.000 description 14
- 239000000126 substance Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 13
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 12
- 239000000047 product Substances 0.000 description 11
- 239000002202 Polyethylene glycol Substances 0.000 description 10
- 229930195733 hydrocarbon Natural products 0.000 description 10
- 229920001223 polyethylene glycol Polymers 0.000 description 10
- VTLYFUHAOXGGBS-UHFFFAOYSA-N Fe3+ Chemical compound [Fe+3] VTLYFUHAOXGGBS-UHFFFAOYSA-N 0.000 description 8
- JEIPFZHSYJVQDO-UHFFFAOYSA-N iron(III) oxide Inorganic materials O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 8
- 239000007789 gas Substances 0.000 description 7
- 229910052757 nitrogen Inorganic materials 0.000 description 6
- 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 5
- 239000010406 cathode material Substances 0.000 description 5
- 238000001816 cooling Methods 0.000 description 5
- 239000012043 crude product Substances 0.000 description 5
- 239000008103 glucose Substances 0.000 description 5
- 238000000227 grinding Methods 0.000 description 5
- 150000002430 hydrocarbons Chemical class 0.000 description 5
- 238000007873 sieving Methods 0.000 description 5
- 239000004215 Carbon black (E152) Substances 0.000 description 4
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 4
- 229940075529 glyceryl stearate Drugs 0.000 description 4
- 239000000376 reactant Substances 0.000 description 4
- 230000009467 reduction Effects 0.000 description 4
- 239000002002 slurry Substances 0.000 description 4
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 3
- MTHSVFCYNBDYFN-UHFFFAOYSA-N diethylene glycol Chemical compound OCCOCCO MTHSVFCYNBDYFN-UHFFFAOYSA-N 0.000 description 3
- 229910000398 iron phosphate Inorganic materials 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 description 2
- 238000005253 cladding Methods 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000007812 deficiency Effects 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000033116 oxidation-reduction process Effects 0.000 description 2
- 239000011163 secondary particle Substances 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 239000011324 bead Substances 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 239000008367 deionised water Substances 0.000 description 1
- 229910021641 deionized water Inorganic materials 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- 238000001035 drying Methods 0.000 description 1
- 230000009977 dual effect Effects 0.000 description 1
- 125000002791 glucosyl group Chemical group C1([C@H](O)[C@@H](O)[C@H](O)[C@H](O1)CO)* 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 229910001416 lithium ion Inorganic materials 0.000 description 1
- 239000002105 nanoparticle Substances 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000011148 porous material Substances 0.000 description 1
- 238000011160 research Methods 0.000 description 1
- 230000005476 size effect Effects 0.000 description 1
- 239000007787 solid Substances 0.000 description 1
- 239000011343 solid material Substances 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
- 238000007740 vapor deposition Methods 0.000 description 1
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 1
- 238000001238 wet grinding 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
- C01B25/45—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
- 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
- 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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- Chemical Kinetics & Catalysis (AREA)
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- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Organic Chemistry (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The embodiment of the application provides a composition for preparing lithium iron phosphate, the lithium iron phosphate, a preparation method of the lithium iron phosphate and a battery anode material, and belongs to the technical field of lithium batteries. The composition for preparing the lithium iron phosphate comprises a ferrophosphorus source and a lithium source, wherein the ferrophosphorus source is ferric phosphate dihydrate, the lithium source is at least one of lithium carbonate and lithium oxalate, and the composition can solve the problem of uneven material mixing in the existing dry mixing mode to a certain extent, so that the performance of the lithium iron phosphate is ensured. In addition, the application also relates to lithium iron phosphate and a preparation method thereof.
Description
Technical Field
The application relates to the technical field of lithium batteries, in particular to a composition for preparing lithium iron phosphate, a preparation method of the lithium iron phosphate and a battery anode material.
Background
In the prior art, lithium iron phosphate has the advantages of high safety, long cycle life, high quality, low price and the like, and is widely applied to lithium ion batteries.
At present, a lithium iron phosphate preparation process generally adopts wet mixing for preparation, however, the wet mixing method has the defects of complex process flow, high preparation cost, low productivity and the like, and is difficult to popularize and apply.
On the basis, in order to simplify the manufacturing process, reduce the manufacturing cost and improve the productivity, technicians begin to adopt a dry mixing method to prepare the lithium iron phosphate, but the existing dry mixing method has the problem of uneven material mixing, so that the performance of the lithium iron phosphate is affected.
Disclosure of Invention
The application aims to provide a composition for preparing lithium iron phosphate, the lithium iron phosphate, a preparation method of the lithium iron phosphate and a battery anode material, which can solve the problem of uneven material mixing in the existing dry mixing mode to a certain extent, so that the performance of the lithium iron phosphate is ensured.
The embodiment of the application is realized as follows:
in a first aspect, embodiments of the present application provide a composition for preparing lithium iron phosphate, including a ferrophosphorus source, a lithium source, and a carbon source, where the ferrophosphorus source is ferric phosphate dihydrate, and the lithium source is at least one of lithium carbonate and lithium oxalate.
In the above technical solution, the reason why the ferric phosphate dihydrate is used as the ferric phosphate source and at least one of lithium carbonate and lithium oxalate is used as the lithium source is that the true density of the ferric phosphate dihydrate is about 2.84g/cm 3 The lithium carbonate and lithium oxalate have a true density of about 2.1g/cm 3 When the phosphorus iron source and the lithium source with the relatively close true densities are mixed in a dry method, the materials can be mixed more uniformly, and therefore the performance of the lithium iron phosphate is ensured.
In some alternative embodiments, the primary particle size of the ferrophosphorus source is 30 to 80nm, and the primary particle size of the lithium source is 20 to 50 nm.
In the technical scheme, the primary particle sizes of the ferrophosphorus source and the lithium source are respectively limited to the ranges of 30-80 nm and 20-50 nm, and the specific range and nanoscale raw materials are directly adopted for mixing, so that the grinding process before dry mixing can be omitted, the preparation process is simplified, the preparation cost is reduced, and the preparation efficiency is improved.
In some alternative embodiments, the ferrophosphorus source has a specific surface area of 40 to 60m 2 The specific surface area of the lithium source is 50-80 m 2 /g。
In the technical scheme, the specific surface areas of the ferrophosphorus source and the lithium source are respectively limited to 40-60 m 2 A/g and 50 to 80m 2 In the range of/g, because the mass of the lithium source only accounts for about 20% of the mass of the ferrophosphorus source in the dry mixing process, the volumes of the ferrophosphorus source and the lithium source can be relatively close to each other by simultaneously limiting the specific surface areas of the ferrophosphorus source and the lithium source in the corresponding ranges, and the uniformity of material mixing is further improved.
In some alternative embodiments, the molar ratio of iron to phosphorus in the iron phosphate dihydrate is (0.96-1): (1-1.04), and/or the molar ratio of lithium to iron in the composition for producing lithium iron phosphate is (1.0-1.04): (0.96-1).
In the technical scheme, the molar ratio of iron to phosphorus in the ferric phosphate dihydrate is limited to (0.96-1): (1-1.04) so that the phosphorus phase is slightly excessive compared with iron, and the iron can be effectively prevented from being introduced in an oxide form, so that the iron oxide is prevented from being reduced into an iron simple substance in a high-temperature reducing atmosphere, and the standard exceeding of magnetic substances in the material is avoided.
Further, the molar ratio of lithium to iron in the composition for producing lithium iron phosphate is limited to (1.0 to 1.04): (0.96-1), so that the lithium phase is slightly excessive compared with iron, firstly, in order to make up for lithium loss caused in the sintering process, secondly, lithium can be preferentially combined with phosphorus, and the lithium is slightly excessive, so that the lithium deficiency of the material can be effectively avoided, and the performance of the lithium iron phosphate is ensured.
In some alternative embodiments, the carbon source comprises at least one of PEG, an ethoxylate, a styrene maleic anhydride resin, citric acid, glyceryl stearate.
In the above technical scheme, at least one of PEG, an ethoxy compound, styrene maleic anhydride resin, citric acid, and glycerol stearate is used as a carbon source, and since PEG, the ethoxy compound, styrene maleic anhydride resin, citric acid, glycerol stearate, and the like can be gasified and decomposed at high temperature into reducing gas and small-molecule hydrocarbons in the sintering process, the double functions of reducing ferric iron into ferrous iron and realizing carbon coating are achieved. Moreover, as the carbon coating is carried out through the gas-phase small-molecular hydrocarbons, compared with the traditional carbon source (the carbon source is liquefied firstly and then decomposed and carbonized in situ in the coating process of the traditional carbon source, the coating uniformity is greatly influenced by the mixing degree of the carbon source), the gas-phase small-molecular hydrocarbons can be fully contacted with the surface of the lithium iron phosphate precursor without being influenced by the mixing degree of the carbon source, so that the uniformity of the carbon coating is ensured.
In some optional embodiments, the mass ratio of the carbon source to the ferrophosphorus source is (0.5-3): 10.
in the technical scheme, the mass ratio of the carbon source to the ferrophosphorus source is limited to (0.5-3): 10, sufficient reducing gas and small-molecule hydrocarbon can be provided after the carbon source is decomposed, and complete reaction in the oxidation-reduction process and the carbon coating process is further ensured.
In a second aspect, an embodiment of the present application provides a method for preparing lithium iron phosphate, including mixing the components of the composition for preparing lithium iron phosphate provided in the first aspect, and then sintering the mixture.
In the technical scheme, the components of the composition for preparing lithium iron phosphate provided by the embodiment of the first aspect are mixed and then sintered to prepare the lithium iron phosphate, so that the uniformity of material mixing can be ensured, and the performance of the lithium iron phosphate is ensured; in some possible embodiments, due to the use of the specific range of nano-scale raw materials, the grinding and crushing steps before mixing can be omitted, thereby simplifying the preparation process, reducing the preparation cost and improving the preparation efficiency.
In some optional embodiments, during the sintering process, the sintering temperature is 700-795 ℃, and the sintering time is 6-10 h.
Among the above-mentioned technical scheme, in the sintering process, inject the sintering temperature in the scope of 700 ~ 795 ℃ to inject the sintering time in the scope of 6 ~ 10h, can guarantee that the reduction of ferric iron and carbon cladding are all gone on under suitable temperature and time length, thereby can avoid ferric iron to be reduced into simple substance iron further, and, can also guarantee the homogeneity of carbon cladding.
In a third aspect, an embodiment of the present application provides lithium iron phosphate, where the lithium iron phosphate is prepared by the method for preparing lithium iron phosphate provided in the embodiment of the second aspect, a 0.1C charging specific capacity of the lithium iron phosphate is greater than 160mAh/g, a 0.1C discharging specific capacity of the lithium iron phosphate is greater than 155mAh/g, and a 0.1C discharging coulombic efficiency of the lithium iron phosphate is greater than 97%.
In the technical scheme, the lithium iron phosphate is prepared by the method for preparing the lithium iron phosphate provided by the embodiment of the second aspect, and the 0.1C charging specific capacity of the prepared lithium iron phosphate is more than 160mAh/g, the 0.1C discharging specific capacity of the lithium iron phosphate is more than 155mAh/g, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate is more than 97%, so that the prepared lithium iron phosphate has excellent electrical properties.
In a fourth aspect, an embodiment of the present application provides a battery cathode material, where the battery cathode material includes the lithium iron phosphate provided in the embodiment of the third aspect.
In the above technical scheme, the battery positive electrode material includes the lithium iron phosphate provided in the embodiment of the third aspect, and performance parameters of the prepared positive electrode material, such as 0.1C specific charge capacity, 0.1C specific discharge coulombic efficiency and the like, can be ensured to be at a higher level, so that the prepared battery positive electrode material has excellent electrical properties.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present application and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained from the drawings without inventive effort.
Fig. 1 is a process flow chart of a method for preparing lithium iron phosphate according to an embodiment of the present disclosure;
fig. 2 is an electron microscope image of lithium iron phosphate provided in embodiment 1 of the present application;
fig. 3 is an electron microscope image of lithium iron phosphate provided in comparative example 1 of the present application;
fig. 4 is an electron microscope image of lithium iron phosphate provided in comparative example 4 of the present application.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application clearer, the technical solutions of the embodiments of the present application will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.
It should be noted that "and/or" in the present application, such as "feature 1 and/or feature 2" refers to "feature 1" alone, "feature 2" alone, and "feature 1" plus "feature 2" alone.
In addition, in the description of the present application, the meaning of "a plurality" of "one or more" means two or more unless otherwise specified; the range of "numerical value a to numerical value b" includes both values "a" and "b", and "unit of measure" in "numerical value a to numerical value b + unit of measure" represents both "unit of measure" of "numerical value a" and "numerical value b".
The composition for preparing lithium iron phosphate, the preparation method thereof, and the battery cathode material according to the embodiments of the present application will be specifically described below.
In the prior art, the preparation of lithium iron phosphate is generally carried out by wet mixing, namely, materials are firstly prepared into slurry with the solid content of 30%, then the slurry is subjected to nano-grinding by a ball mill, then the slurry is prepared into a powdery precursor by spray drying, and finally the powdery precursor is sintered, so that the wet mixing mode has the defects of complex process flow, high preparation cost, low productivity and the like, and is difficult to popularize and apply.
On this basis, technicians begin to adopt a dry mixing method to prepare the lithium iron phosphate, but the existing dry mixing method has the problem of uneven material mixing due to large difference of physical and chemical properties among different raw materials, so that the performance of the lithium iron phosphate is also influenced to a certain extent.
Based on the influence of large difference of physical and chemical properties of reaction raw materials on the mixing uniformity of materials, the inventor researches and discovers that different types of raw materials are selected according to specific parameter requirements in the raw material selection stage, so that the true densities of the different types of raw materials can be as close as possible, the mixing uniformity of the materials can be improved to a certain degree, and the performance of lithium iron phosphate is ensured.
In a first aspect, the present application provides a composition for preparing lithium iron phosphate, including a ferrophosphorus source, a lithium source, and a carbon source, where the ferrophosphorus source is ferric phosphate dihydrate, and the lithium source is at least one of lithium carbonate and lithium oxalate.
In the present application, iron phosphate dihydrate is used as the source of phosphorus iron, and at least one of lithium carbonate and lithium oxalate is used as the source of lithium, since the true density of iron phosphate dihydrate is about 2.84g/cm 3 The lithium carbonate and lithium oxalate have a true density of about 2.1g/cm 3 When the phosphorus iron source and the lithium source with the relatively close true densities are mixed in a dry method, the materials can be mixed more uniformly, and therefore the performance of the lithium iron phosphate is ensured.
The true density refers to the actual mass of a solid material per unit volume of the material in an absolutely dense state, i.e., the density after removal of internal pores or inter-particle voids.
As an example, the ferrophosphorus source has a primary particle size of 30 to 80nm, such as but not limited to any one of 30nm, 40nm, 50nm, 60nm, 70nm and 80nm or a range value therebetween; the lithium source has a primary particle diameter of 20 to 50nm, for example, but not limited to, a primary particle diameter of any one of 20nm, 30nm, 40nm and 50nm or a range between any two of them.
In the embodiment, the primary particle sizes of the ferrophosphorus source and the lithium source are respectively limited to the ranges of 30-80 nm and 20-50 nm, and the specific range and nanoscale raw materials are directly adopted for mixing, so that a grinding process before dry mixing can be omitted, the preparation process is simplified, the preparation cost is reduced, and the preparation efficiency is improved.
The primary particle size refers to the particle size of individual fine grains, and is also referred to as the primary particle size, and the particle size of secondary particles formed after agglomeration is referred to as the secondary particle size.
It should be noted that the material particles are not completely uniform spheres in nature, and therefore, the specific surface area of the material particles under the same particle size standard may be greatly different. In order to avoid a large difference in the specific surface area between the ferrophosphorus source and the lithium source, the specific surface area may be defined.
As an example, the specific surface area of the ferrophosphorus source is 40-60 m 2 A specific surface area of 40m 2 /g、50m 2 G and 60m 2 Any one or a range between any two of,/g; the specific surface area of the lithium source is 50-80 m 2 A specific surface area of, for example but not limited to, 50m 2 /g、60m 2 /g、70m 2 G and 80m 2 Any one of the point values in/g or a range value between any two.
In this embodiment, the specific surface areas of the ferrophosphorus source and the lithium source are respectively limited to 40 to 60m 2 A/g and 50 to 80m 2 In the range of/g, because the mass of the lithium source only accounts for about 20% of the mass of the ferrophosphorus source in the dry mixing process, the volumes of the ferrophosphorus source and the lithium source can be relatively close to each other by simultaneously limiting the specific surface areas of the ferrophosphorus source and the lithium source in the corresponding ranges, and the uniformity of material mixing is further improved.
As an example, the mole ratio of iron to phosphorus in the ferric phosphate dihydrate is (0.96-1): (1-1.04), for example but not limited to, a molar ratio of 0.96: 1. 0.96: 1.04, 1: 1 and 1: 1.04, or a range between any two.
In this embodiment, the molar ratio of iron to phosphorus in the iron phosphate dihydrate is defined as (0.96 to 1): (1-1.04) so that the phosphorus phase is slightly excessive compared with iron, and the iron can be effectively prevented from being introduced in an oxide form, so that the iron oxide is prevented from being reduced into an iron simple substance in a high-temperature reducing atmosphere, and the standard exceeding of magnetic substances in the material is avoided.
As an example, the molar ratio of lithium to iron in the composition for preparing lithium iron phosphate is (1.0-1.04): (0.96-1), for example, but not limited to, a molar ratio of 1: 0.96, 1: 1. 1.04: 0.96 and 1.04: 1, or a range between any two.
In this embodiment, the molar ratio of lithium to iron in the composition for producing lithium iron phosphate is defined as (1.0 to 1.04): (0.96-1), so that the lithium phase is slightly excessive compared with iron, firstly, in order to make up for lithium loss caused in the sintering process, secondly, lithium can be preferentially combined with phosphorus, and the lithium is slightly excessive, so that the lithium deficiency of the material can be effectively avoided, and the performance of the lithium iron phosphate is ensured.
As an example, the carbon source includes at least one of PEG (polyethylene glycol), an ethoxy compound, styrene maleic anhydride resin, citric acid, and glyceryl stearate.
In this embodiment, at least one of PEG, an ethoxy compound, a styrene maleic anhydride resin, citric acid, and glyceryl stearate is used as the carbon source, and PEG, the ethoxy compound, the styrene maleic anhydride resin, citric acid, and glyceryl stearate, etc. are all gasified and decomposed at high temperature into a reducing gas and small-molecule hydrocarbons during sintering, thereby having dual functions of reducing ferric iron into ferrous iron and coating carbon. Moreover, as the carbon coating is carried out through the gas-phase small-molecular hydrocarbons, compared with the traditional carbon source (the carbon source is liquefied firstly and then decomposed and carbonized in situ in the coating process of the traditional carbon source, the coating uniformity is greatly influenced by the mixing degree of the carbon source), the gas-phase small-molecular hydrocarbons can be fully contacted with the surface of the lithium iron phosphate precursor without being influenced by the mixing degree of the carbon source, so that the uniformity of the carbon coating is ensured.
The carbon source is gasified to simultaneously generate reducing gas and small-molecule hydrocarbon, wherein the reducing gas is used for reducing ferric iron into ferrous iron, the small-molecule hydrocarbon is subjected to vapor deposition on the surface of the lithium iron phosphate precursor, and a uniform carbon coating layer is formed on the surface of the lithium iron phosphate precursor through vapor carbon deposition.
It should be noted that the specific type of PEG is not limited.
In some possible embodiments, the PEG is PEG 2000.
In a second aspect, referring to fig. 1, an embodiment of the present application provides a method for preparing lithium iron phosphate, including mixing components of the composition for preparing lithium iron phosphate provided in the first aspect, and then sintering the mixture.
In the application, the components of the composition for preparing lithium iron phosphate provided by the embodiment of the first aspect are mixed and then sintered to prepare the lithium iron phosphate, so that the uniformity of material mixing can be ensured, and the performance of the lithium iron phosphate can be ensured; in some possible embodiments, due to the use of the specific range of nano-scale raw materials, the grinding and crushing steps before mixing can be omitted, thereby simplifying the preparation process, reducing the preparation cost and improving the preparation efficiency.
It will be appreciated that the mixing time may be limited in view of the uniformity of the material mixing.
In some possible embodiments, the mixing time is 1 to 3 hours.
It is noted that the sintering process is carried out in an inert atmosphere in order to create atmospheric conditions for the reduction of the ferric iron and to prevent the generated lithium iron phosphate from being oxidized.
In some possible embodiments, the inert gas comprises at least one of nitrogen and argon.
It should be noted that the type of carbon source may be limited in order to achieve both the reduction of trivalent iron and the uniform carbon coating.
It can be understood that, in consideration of the size uniformity of the lithium iron phosphate, the sintered crude lithium iron phosphate may be sequentially crushed and sieved.
In some possible embodiments, a jet mill is used to sieve the crude lithium iron phosphate, and the crushing pressure is controlled to be 0.4-0.8 Mpa.
In some possible embodiments, the number of screen meshes is greater than 150 meshes.
As an example, the mass ratio of the carbon source to the ferrophosphorus source is (0.5-3): 10, for example but not limited to a mass ratio of 0.5: 10. 1: 10. 2: 10 and 3: 10, or a range between any two.
In this embodiment, the mass ratio of the carbon source to the ferrophosphorus source is defined as (0.5 to 3): within 10, sufficient reducing gas and micromolecular hydrocarbon can be provided after the carbon source is decomposed, and complete reaction in the oxidation-reduction process and the carbon coating process is further ensured.
As an example, during the sintering, the sintering temperature is 700-795 ℃, such as but not limited to, the temperature is 700 ℃, 710 ℃, 720 ℃, 730 ℃, 740 ℃, 750 ℃, 760 ℃, 770 ℃, 780 ℃, 790 ℃ and 795 ℃ or a range value between any two, and the sintering time is 6-10 h, such as but not limited to, the time is 6h, 7h, 8h, 9h and 10h or a range value between any two.
In the embodiment, in the sintering process, the sintering temperature is limited within the range of 700-795 ℃, the sintering time is limited within the range of 6-10 h, and the reduction of the ferric iron and the carbon coating can be ensured to be carried out at appropriate temperature and for long time, so that the ferric iron can be prevented from being further reduced into the simple substance iron, and the uniformity of the carbon coating can be ensured.
When the sintering temperature is higher than 795 ℃, the reducing power of the reducing gas is strong, and Fe is further reduced 2+ Reducing the iron into simple substance iron, thereby causing the standard exceeding of magnetic substances in the lithium iron phosphate and further causing the high self-discharge of the battery.
In a third aspect, an embodiment of the present application provides lithium iron phosphate, where the lithium iron phosphate is prepared by the method for preparing lithium iron phosphate provided in the embodiment of the second aspect, a 0.1C charging specific capacity of the lithium iron phosphate is greater than 160mAh/g, a 0.1C discharging specific capacity of the lithium iron phosphate is greater than 155mAh/g, and a 0.1C discharging coulombic efficiency of the lithium iron phosphate is greater than 97%.
In the application, the lithium iron phosphate is prepared by the preparation method of the lithium iron phosphate provided by the embodiment of the second aspect, and can ensure that the 0.1C charging specific capacity of the prepared lithium iron phosphate is more than 160mAh/g, the 0.1C discharging specific capacity of the lithium iron phosphate is more than 155mAh/g, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate is more than 97%, so that the prepared lithium iron phosphate has excellent electrical properties.
In a fourth aspect, an embodiment of the present application provides a battery cathode material, where the battery cathode material includes the lithium iron phosphate provided in the embodiment of the third aspect.
In the application, the battery positive electrode material comprises the lithium iron phosphate provided by the embodiment of the third aspect, and performance parameters of the prepared positive electrode material, such as the 0.1C charging specific capacity, the 0.1C discharging coulombic efficiency and the like, can be ensured to be in a higher level, so that the prepared battery positive electrode material has excellent electrical performance.
The features and properties of the present application are described in further detail below with reference to examples.
Example 1
The embodiment of the application provides a preparation method of lithium iron phosphate, which comprises the following steps:
and (2) mixing the following components in percentage by mass as 100: 19.6: 27, mixing the dihydrate ferric phosphate, lithium carbonate and PEG2000 in a mixing container for 2 hours to obtain a lithium iron phosphate precursor, wherein the molar ratio of phosphorus to iron in the dihydrate ferric phosphate is 1: 1, the primary particle diameter of the ferric phosphate dihydrate is 30nm, and the specific surface area is 60m 2 (ii)/g, the lithium carbonate having a primary particle diameter of 20nm and a specific surface area of 80m 2 /g；
Transferring the lithium iron phosphate precursor into a tube furnace, sintering at 700 ℃ for 6h under the protection of nitrogen, and naturally cooling to room temperature after sintering to obtain a crude product of lithium iron phosphate;
and sequentially crushing and sieving the crude lithium iron phosphate product to obtain a finished lithium iron phosphate product.
Example 2
The embodiment of the application provides a preparation method of lithium iron phosphate, which comprises the following steps:
and (2) mixing the following components in percentage by mass as 100: 19.6: 13.2 mixing the ferric phosphate dihydrate, the lithium carbonate and the citric acid in a mixing container for 2h to obtain a lithium iron phosphate precursor, wherein the molar ratio of phosphorus to iron in the ferric phosphate dihydrate is 1: 1, the particle diameter of one particle of the ferric phosphate dihydrate is 50nm, and the specific surface area is 50m 2 (ii) the lithium carbonate has a primary particle diameter of 30nm and a specific surface area of 60m 2 /g；
Transferring the lithium iron phosphate precursor into a tube furnace, sintering at 750 ℃ for 6h under the protection of nitrogen, and naturally cooling to room temperature after sintering to obtain a crude product of lithium iron phosphate;
and sequentially crushing and sieving the crude lithium iron phosphate product to obtain a finished lithium iron phosphate product.
Example 3
The embodiment of the application provides a preparation method of lithium iron phosphate, which comprises the following steps:
and (2) mixing the following components in percentage by mass as 100: 27: 27, mixing the dihydrate ferric phosphate, lithium oxalate and the ethoxy compound 450 in a mixing container for 2 hours to obtain a lithium iron phosphate precursor, wherein the molar ratio of phosphorus to iron in the dihydrate ferric phosphate is 1: 1, the primary particle diameter of the ferric phosphate dihydrate is 80nm, and the specific surface area is 40m 2 (ii)/g, the lithium carbonate having a primary particle diameter of 50nm and a specific surface area of 50m 2 /g；
Transferring the lithium iron phosphate precursor into a tube furnace, sintering at 795 ℃ for 10h under the protection of nitrogen, and naturally cooling to room temperature after sintering to obtain a crude product of lithium iron phosphate;
and sequentially crushing and sieving the crude lithium iron phosphate product to obtain a finished lithium iron phosphate product.
Example 4
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from embodiment 1 only in that:
the primary particle size of the ferric phosphate dihydrate is 100nm, and the specific surface area is 30m 2 (iii) lithium carbonate has a primary particle diameter of 200nm and a specific surface area of 10m 2 /g。
Example 5
The embodiment of the present application provides a method for preparing lithium iron phosphate, and the differences of the other embodiments 1 are only that: the primary particle diameter of the ferric phosphate dihydrate is 20nm, and the specific surface area is 80m 2 (iii) lithium carbonate has a primary particle diameter of 10nm and a specific surface area of 100m 2 /g。
Example 6
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from embodiment 1 only in that:
the primary particle size of the ferric phosphate dihydrate was 100 nm.
Example 7
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from embodiment 1 only in that:
the specific surface area of the ferric phosphate dihydrate is 20m 2 /g。
Example 8
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from embodiment 1 only in that:
the primary particle size of lithium carbonate was 200 nm.
Example 9
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from embodiment 1 only in that:
the specific surface area of lithium carbonate is 10m 2 /g。
Example 10
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from embodiment 1 only in that:
PEG2000 was replaced with glucose.
Comparative example 1
The embodiment of the application provides a preparation method of lithium iron phosphate, which comprises the following steps:
and (2) mixing the following components in percentage by mass as 100: 25: 13, mixing the anhydrous iron phosphate, lithium carbonate and glucose in a mixing container for 2 hours to obtain a lithium iron phosphate precursor;
transferring the lithium iron phosphate precursor into a tube furnace, sintering at 700 ℃ for 6h under the protection of nitrogen, and naturally cooling to room temperature after sintering to obtain a crude product of lithium iron phosphate;
and sequentially crushing and sieving the crude lithium iron phosphate product to obtain a finished lithium iron phosphate product.
Comparative example 2
The embodiment of the present application provides a method for preparing lithium iron phosphate, which is different from comparative example 1 only in that:
and (2) mixing the following components in percentage by mass as 100: 19.6: 13, mixing the ferric phosphate dihydrate, the lithium carbonate and the glucose in a mixing container for 2 hours to obtain a lithium iron phosphate precursor.
Comparative example 3
The embodiment of the application provides a preparation method of lithium iron phosphate, which is different from the comparative example 1 only in that:
and (2) mixing the following components in percentage by mass as 100: 25: 27 anhydrous iron phosphate, lithium carbonate and PEG2000 were mixed in a mixing container for 2h to obtain a lithium iron phosphate precursor.
Comparative example 4
The embodiment of the application provides a preparation method of lithium iron phosphate, which comprises the following steps:
and (2) mixing the following components in percentage by mass as 100: 25: 13: 300 of anhydrous iron phosphate, lithium carbonate, glucose and deionized water are mixed in a mixing container for 2 hours to obtain a lithium iron phosphate precursor, then the slurry is ground to the particle size of 0.45 mu m by a bead mill, and then spray drying is carried out;
transferring the lithium iron phosphate precursor into a tube furnace, sintering at 700 ℃ for 6h under the protection of nitrogen, and naturally cooling to room temperature after sintering to obtain a crude product of lithium iron phosphate;
and sequentially crushing and sieving the crude lithium iron phosphate product to obtain a finished lithium iron phosphate product.
Test example 1
Electrical property test of lithium iron phosphate material
The testing method comprises the step of respectively adopting GBT 30835 and 2014 appendix F testing methods to test the electrical properties of 13 groups of lithium iron phosphate materials prepared in the embodiments 1-10 and the comparative examples 1-4.
TABLE 1 Electrical Performance test Structure
Referring to table 1, from the test results of examples 1 to 3, when the material mixture ratio, the physical and chemical performance parameters of the reactant, the process parameters, and the like are within the set ranges, the 0.1C charging specific capacity of the prepared lithium iron phosphate is greater than 160mAh/g, the 0.1C discharging specific capacity of the lithium iron phosphate is greater than 155mAh/g, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate is greater than 97%, which indicates that the lithium iron phosphate prepared in examples 1 to 3 has excellent electrical properties.
From the test results of example 1 and example 4, it is known that when the particle size of the iron phosphate dihydrate and the primary particle size of the lithium carbonate are larger than the set ranges, and the specific surface area of the iron phosphate dihydrate are smaller than the set ranges, the 0.1C charging specific capacity of the lithium iron phosphate prepared in example 4, the 0.1C discharging specific capacity of the lithium iron phosphate, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate are all lower than those of example 1, which indicates that the particle size and the specific surface area of the iron phosphate dihydrate and the primary particle size and the specific surface area of the lithium carbonate are limited within the set ranges, and the prepared lithium iron phosphate can be ensured to have excellent electrical properties.
From the test results of example 1 and example 5, it is known that when the particle size of the iron phosphate dihydrate and the primary particle size of the lithium carbonate are smaller than the set ranges, and the specific surface area of the iron phosphate dihydrate are larger than the set ranges, the 0.1C charging specific capacity of the lithium iron phosphate prepared in example 4, the 0.1C discharging specific capacity of the lithium iron phosphate, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate are all lower than those of example 1, which indicates that the particle size and the specific surface area of the iron phosphate dihydrate and the primary particle size and the specific surface area of the lithium carbonate are limited within the set ranges, and the prepared lithium iron phosphate can be ensured to have excellent electrical properties.
From the test results of the embodiment 1 and the embodiments 6 to 7, it can be known that when the particle size or the specific surface area of the iron phosphate dihydrate is not within the set range, the 0.1C charging specific capacity of the prepared lithium iron phosphate, the 0.1C discharging specific capacity of the lithium iron phosphate, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate are all lower than those of the embodiment 1, which indicates that the particle size and the specific surface area of the iron phosphate dihydrate are limited within the set range, and the prepared lithium iron phosphate has excellent electrical properties.
From the test results of example 1 and examples 8 to 9, it is known that when the particle size or specific surface area of one particle of lithium carbonate is not within the set range, the 0.1C specific charging capacity of the prepared lithium iron phosphate, the 0.1C specific discharging capacity of the lithium iron phosphate, and the 0.1C coulombic discharging efficiency of the lithium iron phosphate are all lower than those of example 1, which indicates that the primary particle size and specific surface area of lithium carbonate are limited within the set range, and the prepared lithium iron phosphate can be ensured to have excellent electrical properties.
From the test results of the embodiment 1 and the embodiment 10, when the carbon source is replaced with the conventional carbon source (glucose), the 0.1C charging specific capacity of the prepared lithium iron phosphate, the 0.1C discharging specific capacity of the lithium iron phosphate, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate are all significantly reduced, which indicates that the carbon coating uniformity can be ensured to a certain extent by selecting a specific carbon source in the raw material selection stage, thereby ensuring the performance of the lithium iron phosphate.
It can be known from the test results of the embodiments 1 to 3 and the comparative examples 1 to 3 that the 0.1C charging specific capacity of the prepared lithium iron phosphate, the 0.1C discharging specific capacity of the lithium iron phosphate, and the 0.1C discharging coulombic efficiency of the lithium iron phosphate are all significantly reduced by adopting the conventional dry mixing (i.e., no specific selection is performed on the reaction materials), which indicates that different types of raw materials are selected according to specific parameter requirements at the raw material selection stage, so that the physical and chemical properties of the different types of raw materials can be as close as possible, the uniformity of material mixing and carbon coating can be improved to a certain extent, and thus the performance of the lithium iron phosphate can be ensured.
It can be known from the test results of examples 1 to 3 and comparative example 4 that different types of raw materials are selected according to specific parameter requirements in the raw material selection stage, so that the physicochemical properties of the different types of raw materials are as close as possible, and the uniformity of material mixing and carbon coating can be improved to a certain extent, so that lithium iron phosphate with the same excellent electrical properties as those prepared by a wet mixing method can be obtained.
More importantly, the preparation method provided by the embodiment of the application can omit a wet grinding process and a drying step after mixing due to the adoption of the nano-scale raw materials for mixing, thereby achieving the purposes of simplifying the preparation process, reducing the preparation cost and improving the preparation efficiency.
Therefore, the purposes of simplifying the preparation process, reducing the preparation cost and improving the preparation efficiency can be realized while the high-performance lithium iron phosphate is prepared by selecting the reaction materials (namely selecting the phosphorus iron source and the lithium source with the similar true densities to mix and limiting the sizes of the phosphorus iron source and the lithium source to be nano-sized, and in addition, the carbon source selection can prevent the carbon coating process from being influenced by the mixing uniformity of the carbon source).
Test example 2
Electron microscope test of lithium iron phosphate material
The test method comprises the following steps: the lithium iron phosphate prepared in example 1, comparative example 1 and comparative example 4 was subjected to morphology testing by an electron microscope.
As can be seen from fig. 2 and 3, when the material ratio, the physical and chemical properties of the reactant, and the process parameters are all within the set ranges, the particle size of the prepared lithium iron phosphate is smaller and the uniformity is better than that of the conventional dry mixing method (i.e., the specific selection of the reactant is not performed).
As can be seen from fig. 2 and 4, when the material ratio, the physical and chemical performance parameters of the reactant, and the process parameters are within the set ranges, the particle size effect of the prepared lithium iron phosphate is closer to that of the lithium iron phosphate prepared by the wet mixing method, i.e., the particle size is smaller and the uniformity is good.
The embodiments described above are some, but not all embodiments of the present application. The detailed description of the embodiments of the present application is not intended to limit the scope of the claimed application, but is merely representative of selected embodiments of the application. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present application.
Claims (10)
1. The composition for preparing lithium iron phosphate is characterized by comprising a phosphorus iron source, a lithium source and a carbon source, wherein the phosphorus iron source is ferric phosphate dihydrate, and the lithium source is at least one of lithium carbonate and lithium oxalate.
2. The composition for preparing lithium iron phosphate according to claim 1, wherein the primary particle size of the ferrophosphorus source is 30 to 80nm, and the primary particle size of the lithium source is 20 to 50 nm.
3. The composition for preparing lithium iron phosphate according to claim 2, wherein the specific surface area of the ferrophosphorus source is 40-60 m 2 The specific surface area of the lithium source is 50-80 m 2 /g。
4. The composition for preparing lithium iron phosphate according to claim 1, wherein the molar ratio of iron to phosphorus in the iron phosphate dihydrate is (0.96-1): (1-1.04), and/or the molar ratio of lithium to iron in the composition for preparing lithium iron phosphate is (1.0-1.04): (0.96-1).
5. The composition for preparing lithium iron phosphate according to any one of claims 1 to 4, wherein the carbon source comprises at least one of PEG, an ethoxy compound, a styrene maleic anhydride resin, citric acid and glycerol stearate.
6. The composition for preparing lithium iron phosphate according to claim 5, wherein the mass ratio of the carbon source to the ferrophosphorus source is (0.5-3): 10.
7. the preparation method of the lithium iron phosphate is characterized by comprising the following steps:
the lithium iron phosphate preparation composition according to any one of claims 1 to 6, wherein the components are mixed and then sintered.
8. The method for preparing lithium iron phosphate according to claim 7, wherein in the sintering process, the sintering temperature is 700-795 ℃ and the sintering time is 6-10 h.
9. Lithium iron phosphate, characterized in that it is prepared by the method for preparing lithium iron phosphate according to claim 7 or 8, and has a 0.1C specific charging capacity of more than 160mAh/g, a 0.1C specific discharging capacity of more than 155mAh/g, and a 0.1C coulombic discharging efficiency of more than 97%.
10. A battery positive electrode material, characterized by comprising the lithium iron phosphate according to claim 9.
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