CN117602603A - Nanometer ferric phosphate and preparation method thereof, nanometer lithium ferric phosphate positive electrode material and preparation method and application thereof - Google Patents
Nanometer ferric phosphate and preparation method thereof, nanometer lithium ferric phosphate positive electrode material and preparation method and application thereof Download PDFInfo
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- CN117602603A CN117602603A CN202311588090.6A CN202311588090A CN117602603A CN 117602603 A CN117602603 A CN 117602603A CN 202311588090 A CN202311588090 A CN 202311588090A CN 117602603 A CN117602603 A CN 117602603A
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- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 title claims abstract description 97
- 239000005955 Ferric phosphate Substances 0.000 title claims abstract description 74
- 229940032958 ferric phosphate Drugs 0.000 title claims abstract description 74
- 229910000399 iron(III) phosphate Inorganic materials 0.000 title claims abstract description 74
- 238000002360 preparation method Methods 0.000 title claims abstract description 45
- 229910052744 lithium Inorganic materials 0.000 title claims abstract description 33
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 title claims abstract description 21
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 20
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 76
- 239000002243 precursor Substances 0.000 claims abstract description 75
- 239000002002 slurry Substances 0.000 claims abstract description 60
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 44
- 239000010405 anode material Substances 0.000 claims abstract description 32
- 238000010438 heat treatment Methods 0.000 claims abstract description 32
- 239000004094 surface-active agent Substances 0.000 claims abstract description 31
- 238000000034 method Methods 0.000 claims abstract description 26
- 238000006243 chemical reaction Methods 0.000 claims abstract description 25
- 238000003756 stirring Methods 0.000 claims abstract description 23
- 229910052742 iron Inorganic materials 0.000 claims abstract description 21
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 19
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 15
- 238000000975 co-precipitation Methods 0.000 claims abstract description 15
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 15
- 239000011574 phosphorus Substances 0.000 claims abstract description 15
- 238000005245 sintering Methods 0.000 claims description 81
- 239000000243 solution Substances 0.000 claims description 66
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 48
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 45
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 42
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 32
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 32
- 229910000398 iron phosphate Inorganic materials 0.000 claims description 27
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 24
- 238000002156 mixing Methods 0.000 claims description 19
- 238000005406 washing Methods 0.000 claims description 18
- 239000011790 ferrous sulphate Substances 0.000 claims description 14
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 14
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 14
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 14
- 230000032683 aging Effects 0.000 claims description 13
- 238000001354 calcination Methods 0.000 claims description 11
- 239000011259 mixed solution Substances 0.000 claims description 11
- 239000007800 oxidant agent Substances 0.000 claims description 10
- 238000002425 crystallisation Methods 0.000 claims description 8
- 230000008025 crystallization Effects 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 8
- 239000011261 inert gas Substances 0.000 claims description 8
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 7
- 229910001416 lithium ion Inorganic materials 0.000 claims description 7
- 230000001590 oxidative effect Effects 0.000 claims description 7
- 230000008569 process Effects 0.000 claims description 7
- 230000001105 regulatory effect Effects 0.000 claims description 7
- LZZYPRNAOMGNLH-UHFFFAOYSA-M Cetrimonium bromide Chemical compound [Br-].CCCCCCCCCCCCCCCC[N+](C)(C)C LZZYPRNAOMGNLH-UHFFFAOYSA-M 0.000 claims 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 claims description 6
- 239000002202 Polyethylene glycol Substances 0.000 claims description 6
- 239000008103 glucose Substances 0.000 claims description 6
- 229920001223 polyethylene glycol Polymers 0.000 claims description 6
- 239000012716 precipitator Substances 0.000 claims description 6
- 239000011164 primary particle Substances 0.000 claims description 6
- 230000001276 controlling effect Effects 0.000 claims description 4
- HEBRGEBJCIKEKX-UHFFFAOYSA-M sodium;2-hexadecylbenzenesulfonate Chemical compound [Na+].CCCCCCCCCCCCCCCCC1=CC=CC=C1S([O-])(=O)=O HEBRGEBJCIKEKX-UHFFFAOYSA-M 0.000 claims description 4
- 230000002431 foraging effect Effects 0.000 claims description 3
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 2
- 239000004254 Ammonium phosphate Substances 0.000 claims description 2
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 2
- 229930006000 Sucrose Natural products 0.000 claims description 2
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 2
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 2
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 2
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019289 ammonium phosphates Nutrition 0.000 claims description 2
- 238000000498 ball milling Methods 0.000 claims description 2
- WQZGKKKJIJFFOK-VFUOTHLCSA-N beta-D-glucose Chemical compound OC[C@H]1O[C@@H](O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-VFUOTHLCSA-N 0.000 claims description 2
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 2
- QKIAYRRGJHLRAQ-UHFFFAOYSA-N hexadecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 QKIAYRRGJHLRAQ-UHFFFAOYSA-N 0.000 claims description 2
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 2
- 235000011007 phosphoric acid Nutrition 0.000 claims description 2
- 229920000058 polyacrylate Polymers 0.000 claims description 2
- 239000005720 sucrose Substances 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000006012 monoammonium phosphate Substances 0.000 claims 1
- 239000002245 particle Substances 0.000 abstract description 35
- 239000013078 crystal Substances 0.000 abstract description 14
- 239000000463 material Substances 0.000 abstract description 4
- 238000002474 experimental method Methods 0.000 abstract 1
- 239000007787 solid Substances 0.000 description 16
- 239000010406 cathode material Substances 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 8
- 238000001878 scanning electron micrograph Methods 0.000 description 8
- 238000005303 weighing Methods 0.000 description 7
- 238000001816 cooling Methods 0.000 description 5
- 238000000227 grinding Methods 0.000 description 5
- 239000002105 nanoparticle Substances 0.000 description 4
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 4
- 230000002378 acidificating effect Effects 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 235000014413 iron hydroxide Nutrition 0.000 description 2
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 2
- 239000000203 mixture Substances 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 239000003153 chemical reaction reagent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000002360 explosive Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 239000007788 liquid Substances 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- DPTATFGPDCLUTF-UHFFFAOYSA-N phosphanylidyneiron Chemical compound [Fe]#P DPTATFGPDCLUTF-UHFFFAOYSA-N 0.000 description 1
- 238000001556 precipitation Methods 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 239000012798 spherical particle Substances 0.000 description 1
- 238000005728 strengthening Methods 0.000 description 1
- 230000009466 transformation Effects 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B32/00—Carbon; Compounds thereof
- C01B32/05—Preparation or purification of carbon not covered by groups C01B32/15, C01B32/20, C01B32/25, C01B32/30
-
- 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
-
- 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
- H01M4/583—Carbonaceous material, e.g. graphite-intercalation compounds or CFx
- H01M4/587—Carbonaceous material, e.g. graphite-intercalation compounds or CFx for inserting or intercalating light metals
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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/01—Particle morphology depicted by an image
- C01P2004/03—Particle morphology depicted by an image obtained by SEM
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- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/62—Submicrometer sized, i.e. from 0.1-1 micrometer
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- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/60—Particles characterised by their size
- C01P2004/64—Nanometer sized, i.e. from 1-100 nanometer
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- C01P2006/40—Electric properties
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- 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
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- General Chemical & Material Sciences (AREA)
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Abstract
The invention discloses a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof, belonging to the technical field of lithium battery materials, and the preparation method of the nano ferric phosphate provided by the invention comprises the following steps: and preparing first precursor slurry from an iron source and a phosphorus source by adopting a coprecipitation method, adding a surfactant, adding a precipitant under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain the nano ferric phosphate. And adding a surfactant into the first precursor slurry obtained by the coprecipitation reaction, so that the generation of large particles can be inhibited in the growth stage of ferric phosphate crystal grains, and then the stable and uniform growth of the crystal grains is controlled, so that the nano ferric phosphate is obtained. The nanometer ferric phosphate, the lithium source and the carbon source are mixed and sintered to obtain the nanometer ferric phosphate lithium anode material, and experiments prove that: the nano ferric phosphate is converted into nano lithium iron phosphate, and the morphology and the volume corresponding to the nano lithium iron phosphate are not changed excessively.
Description
Technical Field
The invention relates to the technical field of lithium battery materials, in particular to a nano ferric phosphate and a preparation method thereof, a nano ferric phosphate lithium positive electrode material and a preparation method and application thereof.
Background
The lithium iron phosphate is an important positive electrode material of a lithium ion battery, and has the advantages of high structural stability, good safety performance, moderate working voltage, good platform characteristic, large theoretical capacity and the like, however, the existing lithium iron phosphate has the problems of uneven particles, large granularity, small specific surface area and the like. This results in a fabricated battery with low volumetric specific capacity and poor electrochemical performance.
Disclosure of Invention
The invention aims to overcome the defects in the prior art and provide a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof.
The invention solves the technical problems by adopting the following technical scheme.
The invention provides a preparation method of nano ferric phosphate, which comprises the following steps: preparing first precursor slurry by adopting a coprecipitation method for an iron source and a phosphorus source, adding a surfactant, adding a precipitator under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain nano ferric phosphate, wherein the method comprises the following steps: the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzene sulfonate.
The invention also provides the nano iron phosphate prepared by the preparation method, wherein the primary particle size of the nano iron phosphate is 50-150 nm, and the morphology of the nano iron phosphate is spherical or spheroid.
The invention also provides a preparation method of the nano lithium iron phosphate anode material, which comprises the following steps: and mixing and sintering the prepared nano ferric phosphate, lithium source and carbon source in inert gas atmosphere to obtain the nano lithium ferric phosphate anode material.
The invention also provides the nano lithium iron phosphate anode material prepared by the preparation method, wherein the primary particle size of the nano lithium iron phosphate anode material is 150-250 nm, and the morphology of the nano lithium iron phosphate anode material is spherical or spheroid.
The invention also provides a lithium ion battery, which comprises the nano lithium iron phosphate anode material.
The invention has the following beneficial effects:
the invention provides a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof, and the preparation method of the nano ferric phosphate comprises the following steps: preparing first precursor slurry by adopting a coprecipitation method for an iron source and a phosphorus source, adding a surfactant, adding a precipitator under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain nano ferric phosphate, wherein the method comprises the following steps: the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzene sulfonate. In the preparation process of the nano ferric phosphate, a coprecipitation method is firstly adopted to prepare and form a first precursor slurry, and then a surfactant is added, so that on one hand, the surfactant can inhibit the growth of crystal nucleus of a precipitation product to obtain more uniform nano ferric phosphate particles, and on the other hand, in the process of preparing the nano ferric phosphate lithium anode material by mixing and sintering nano ferric phosphate, a lithium source and a carbon source, the surfactant can also be used as a part of carbon source to be distributed in the nano ferric phosphate lithium anode material, and the conductivity and the ion conductivity of the finished nano ferric phosphate lithium anode material are improved. The method is unique and effective in preparation, and the prepared nano lithium iron phosphate positive electrode material is uniform in appearance, fine in particles, spherical or spheroidic, good in conductivity and high in stability.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings that are needed in the embodiments will be briefly described below, it being understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and other related drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is an SEM image of nano-sized iron phosphate prepared according to example 1;
fig. 2 is an SEM image of the nano lithium iron phosphate cathode material prepared in example 1;
FIG. 3 is an SEM image of nano-sized iron phosphate prepared according to example 2;
fig. 4 is an SEM image of the nano lithium iron phosphate cathode material prepared in example 2;
FIG. 5 is an SEM image of nano-sized iron phosphate prepared according to example 3;
fig. 6 is an SEM image of the nano lithium iron phosphate cathode material prepared in example 3;
fig. 7 is an SEM image of nano iron phosphate prepared in comparative example 1;
fig. 8 is an SEM image of the nano lithium iron phosphate cathode material prepared in comparative example 1.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more clear, the technical solutions of the embodiments of the present invention will be clearly and completely described below. 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.
The embodiment of the invention provides a nano ferric phosphate and a preparation method thereof, a nano lithium iron phosphate positive electrode material and a preparation method and application thereof.
In a first aspect, an embodiment of the present invention provides a method for preparing nano iron phosphate, including: preparing first precursor slurry by adopting a coprecipitation method for an iron source and a phosphorus source, adding a surfactant, adding a precipitator under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain nano ferric phosphate, wherein the method comprises the following steps: the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzene sulfonate.
The embodiment of the invention provides a preparation method of nano ferric phosphate, which comprises the steps of firstly adopting a coprecipitation method to perform explosive nucleation in a solution to obtain first precursor slurry, then adding a surfactant into the first precursor slurry, improving interfacial adsorption by the affinity between the surfactant and ferric phosphate crystal grains, reducing the surface energy of the ferric phosphate crystal grains, thereby effectively inhibiting the growth process of the crystal grains, and then controlling the reaction temperature and pH value of the solution to enable the crystal grains in the solution to stably grow to obtain second precursor slurry, and then carrying out aftertreatment on the second precursor slurry to obtain the nano ferric phosphate.
In an alternative embodiment, the method comprises the steps of: adjusting the pH value of the mixed solution of the iron source and the phosphorus source to 1-2, and then carrying out coprecipitation reaction with an oxidant to obtain first precursor slurry; then uniformly mixing the first precursor slurry with a surfactant, adding a precipitant under the condition of stirring and heating to maintain the pH of the reaction at 1-2, and obtaining a second precursor slurry after the reaction is finished; and aging, washing and calcining the second precursor slurry to obtain the nano ferric phosphate.
In an alternative embodiment, the preparation of the first precursor slurry comprises: mixing an iron source solution and a phosphorus source solution to obtain a mixed solution, regulating the pH value of the mixed solution to 1-2, and then adding an excessive oxidant solution to perform coprecipitation reaction to obtain a first precursor slurry;
preferably, the iron source comprises: at least one of ferrous sulfate and iron powder, wherein the phosphorus source comprises at least one of phosphoric acid, ammonium phosphate and ammonium dihydrogen phosphate, the concentration of the iron source solution is 1-3 mol/L, and the concentration of the phosphorus source solution is 1-3 mol/L;
preferably, the pH of the mixed solution is regulated to 1-2 by using sulfuric acid solution, and the concentration of the sulfuric acid solution is 1-3 mol/L;
preferably, the oxidizing agent is hydrogen peroxide, and the molar ratio of the iron source to the hydrogen peroxide is 1: (0.55-0.75), the concentration of the oxidant solution is 1-4 mol/L;
preferably, the temperature of the coprecipitation reaction is 80-90 ℃ and the time is 1-3 h.
In the above preparation process of the first precursor slurry, it is necessary to mix the iron source solution and the phosphorus source solution to obtain a mixed solution, and then adjust the pH of the mixed solution to 1 to 2, and if the pH is 2 or more, it is necessary to control the pH of the mixed solution to 1 to 2 because the formation of iron hydroxide impurities is caused according to the solubility product of iron hydroxide.
In an alternative embodiment, the preparation of the second precursor slurry comprises: uniformly mixing the first precursor slurry and a surfactant, dropwise adding a precipitator step by step under the condition of stirring and heating, and controlling the pH value of the reaction to be 1-2 to obtain the second precursor slurry;
preferably, the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium cetylbenzenesulfonate, more preferably citric acid;
preferably, the content of the surfactant in the second precursor slurry is 0.2-1 g/500ml, the stirring speed is 400-700 rpm, and the heating temperature is 80-90 ℃;
preferably, the precipitant comprises at least one of sodium hydroxide solution and ammonia water, and the concentration of the precipitant is 1-4 mol/L;
preferably, the total dripping time of the precipitant is controlled to be 20-40 min, and the pH value of the final solution is 1-2 after the dripping of the precipitant is finished.
In the preparation process of the second precursor slurry, the first precursor slurry and the surfactant are uniformly mixed, and under the condition of stirring and heating, the precipitant is dropwise added into the mixture step by step, and the pH value of the reaction is controlled to be 1-2. Stirring and heating are used for strengthening the affinity between the crystal grains and the surfactant, exerting the capability of the surfactant to inhibit the growth of the crystal grains, and simultaneouslyStirring can also suppress the generation of large particles, and during the coprecipitation reaction of the mixed liquid of the iron source and the phosphorus source with the oxidizing agent, the following reaction occurs: 2Fe 2+ +2H 2 PO 4 - +H 2 O 2 ＝2FePO 4 +2H 2 O+2H + H is associated with the whole reaction process + After phosphoric acid and oxidant are added initially, the reaction is more acidic, and the whole reaction is more acidic when being stirred and heated, a precipitant can absorb a large amount of H generated by the reaction + So that the pH is stabilized at 1-2. By controlling the reaction temperature and the pH value of the first precursor slurry, the grains can be continuously and stably generated into nano ferric phosphate particles with uniform particle size.
In an alternative embodiment, the preparation of the nano-sized iron phosphate comprises: filtering and washing the second precursor slurry, adding a phosphoric acid solution for aging and crystallization, filtering and washing again, and calcining to obtain nano ferric phosphate;
preferably, in the aging crystallization process, the stirring rotation speed is 300-700 rpm, the heating temperature is 80-90 ℃, and the aging time is 2-4 hours;
preferably, the concentration of the phosphoric acid solution is 1-3 mol/L;
preferably, the calcination temperature is 550 to 650 ℃ and the time is 4 to 6 hours.
In the preparation process of the nano ferric phosphate, the second precursor slurry is filtered and washed, and then is added with the phosphoric acid solution for aging crystallization, so that impurity ions are removed by the aging crystallization, the iron-phosphorus ratio is adjusted, a more complete crystal form can be obtained, a foundation is laid for the subsequent growth of a better nano lithium iron phosphate crystal form structure, the aging crystallization is carried out under the condition of stirring and heating for promoting the transformation of crystals, and the crystal form of the nano ferric phosphate cannot be changed if the aging crystallization is not heated.
In a second aspect, the embodiment of the invention also provides the nano iron phosphate prepared by the preparation method, wherein the primary particle size of the nano iron phosphate is 50-150 nm, and the morphology of the nano iron phosphate is spherical or spheroid.
In a third aspect, an embodiment of the present invention further provides a method for preparing a nano lithium iron phosphate cathode material, including: and mixing and sintering the prepared nano ferric phosphate, lithium source and carbon source in inert gas atmosphere to obtain the nano lithium ferric phosphate anode material.
In an alternative embodiment, mixing and grinding nano ferric phosphate, a lithium source and a carbon source to obtain a nano lithium iron phosphate precursor, and then sintering and cooling the nano lithium iron phosphate precursor to obtain a nano lithium iron phosphate anode material;
preferably, mixing nano ferric phosphate, a lithium source and a carbon source according to the molar ratio of (2-2.5): (1-1.50): (0.2-0.4), and then ball-milling for 4-6 hours at the rotating speed of 200-400 rpm to obtain a nano ferric phosphate lithium precursor;
preferably, the carbon source comprises at least one of glucose, sucrose, and polyacrylate;
preferably, the sintering comprises one-stage sintering, two-stage sintering and three-stage sintering, wherein the one-stage sintering is performed by adopting a first heating rate to raise the temperature from room temperature to a first sintering temperature, and the first sintering time is maintained; the second-stage sintering is to increase the temperature from the first sintering temperature to the second sintering temperature by adopting a second heating rate, and the second sintering time is kept; the third-stage sintering is to adopt a third heating rate to rise from the second sintering temperature to a third sintering temperature, and the third sintering time is kept;
more preferably, the first sintering temperature is 30 to 50 ℃, and the first sintering time period is 1 to 2 hours; the second sintering temperature is 550-600 ℃, and the second sintering time is 3-4 hours; the third sintering temperature is 700-750 ℃, and the third sintering time is 7-10 hours;
more preferably, the first heating rate is 10deg.C/min, the second heating rate is 5deg.C/min, and the third heating rate is 2deg.C/min.
In the preparation process of the nano lithium iron phosphate anode material, the prepared nano iron phosphate, lithium source and carbon source are mixed and sintered in inert gas atmosphere, and as the surfactant is utilized to inhibit the growth of crystal grains in the preparation process of the nano iron phosphate, the surfactant can be also used as a part of carbon source to be distributed in the nano lithium iron phosphate in the calcination process, so that the conductivity and the conductivity of the finished nano lithium iron phosphate anode material are improved; in the subsequent sintering process, the overall sintering temperature is lower, and the nano spherical lithium iron phosphate anode material with better particle distribution can be obtained. Meanwhile, in the process of preparing the nano lithium iron phosphate positive electrode material, a carbon source is added, and the carbon source is calcined at a high temperature, so that a continuous or discontinuous carbon coating layer can be formed on the surface of the nano lithium iron phosphate positive electrode material, or carbon particles can be formed in gaps of the nano lithium iron phosphate positive electrode material, and the conductivity of the nano lithium iron phosphate positive electrode material is further improved.
In a fourth aspect, the embodiment of the invention also provides a nano lithium iron phosphate anode material prepared by the preparation method, wherein the primary particle size of the nano lithium iron phosphate anode material is 150-250 nm, and the morphology of the nano lithium iron phosphate anode material is spherical or spheroid.
The morphology difference of the nano ferric phosphate and the nano lithium iron phosphate anode material provided by the embodiment of the invention is small, namely the morphology and the volume corresponding to the nano ferric phosphate to nano lithium iron phosphate anode material are not changed excessively. The morphology of the nano lithium iron phosphate positive electrode material is proved to be feasible to be regulated and controlled by the surfactant. Therefore, the particle morphology of the nano ferric phosphate is mainly regulated to solve the problems of the particle size and morphology of the nano ferric phosphate, and the nano spherical particle lithium iron phosphate anode material is provided, and has the advantages of uniform particles, small particle size, large specific surface area, low resistivity and the like.
In a fifth aspect, an embodiment of the present invention provides a lithium ion battery, where the lithium ion battery includes the above-mentioned nano lithium iron phosphate cathode material.
The features and capabilities of the present invention are described in further detail below in connection with the examples.
Example 1
The preparation method of the lithium iron phosphate anode material comprises the following steps:
(1) Weighing ferrous sulfate, hydrogen peroxide, sodium hydroxide, phosphoric acid and sulfuric acid, respectively dissolving in water, and preparing a ferrous sulfate solution with the concentration of 1mol/L, a hydrogen peroxide solution with the concentration of 1mol/L, a sodium hydroxide solution with the concentration of 1mol/L, a phosphoric acid solution with the concentration of 1mol/L and a sulfuric acid solution with the concentration of 1 mol/L;
(2) Ferrous sulfate and phosphoric acid at 1:1, obtaining 500mL of solution, adding sulfuric acid solution, adjusting the pH to 1, adding excessive hydrogen peroxide solution (the molar ratio of an iron source to hydrogen peroxide is 1:0.55), and reacting for 1 hour to obtain first precursor slurry;
(3) Weighing 0.2g of citric acid, adding the citric acid into the first precursor slurry, stirring and dissolving, stirring and heating at 80 ℃ and 400rpm, dropwise adding a sodium hydroxide solution step by step, ending dropwise adding within 20min, and finally obtaining a second precursor slurry with the pH of 1, filtering and washing to obtain a solid;
(4) Fully washing the solid, adding a phosphoric acid solution, aging and crystallizing for 2 hours at 90 ℃, and fully washing the solid;
(5) Calcining the aged solid at 550 ℃ for 4 hours to dehydrate, and finally obtaining spherical or spheroidic nano ferric phosphate;
(6) Mixing and grinding the prepared nano ferric phosphate with a lithium source and glucose in a molar ratio of 2:1.03:0.3 to obtain a nano ferric phosphate lithium precursor;
sintering the prepared nano lithium iron phosphate precursor in an inert gas atmosphere, wherein: the sintering is performed in three sections, the first sintering temperature is 30 ℃, and the first sintering time is 1 hour; the second sintering temperature is 550 ℃, and the second sintering time is 3 hours; the third sintering temperature is 700 ℃, and the third sintering time is 7 hours; and cooling to obtain the nano-scale spherical or spheroidic lithium iron phosphate anode material.
Fig. 1 and 2 are Scanning Electron Microscope (SEM) images of the nano-iron phosphate and nano-lithium iron phosphate cathode materials prepared in example 1, respectively. It can be seen that the particles in both figures are spherical or spheroid, with a particle size of 90nm for iron phosphate and 160nm for lithium iron phosphate. The whole particles are uniformly distributed and regular in morphology, and the morphology and volume corresponding to the conversion from ferric phosphate to lithium iron phosphate are not changed excessively.
Example 2
The preparation method of the lithium iron phosphate anode material comprises the following steps:
(1) Weighing ferrous sulfate, hydrogen peroxide, sodium hydroxide, phosphoric acid and sulfuric acid, respectively dissolving in water, and preparing ferrous sulfate solution with concentration of 2mol/L, hydrogen peroxide solution with concentration of 2mol/L, sodium hydroxide solution with concentration of 2mol/L, phosphoric acid solution with concentration of 2mol/L and sulfuric acid solution with concentration of 2 mol/L;
(2) Ferrous sulfate and phosphoric acid at 1:1 to obtain 500mL solution, adding sulfuric acid solution, adjusting pH to 1.5, adding excessive hydrogen peroxide solution (the molar ratio of an iron source to hydrogen peroxide is 1:0.55), and reacting for 2 hours to obtain first precursor slurry;
(3) Weighing 0.5g of citric acid, adding the citric acid into the first precursor slurry, stirring and dissolving, stirring and heating at 85 ℃ and 550rpm, dropwise adding a sodium hydroxide solution into the mixture step by step, ending dropwise adding within 30min, and finally obtaining a second precursor slurry with the pH of 1.5, filtering and washing to obtain a solid;
(4) Fully washing the solid, adding a phosphoric acid solution, aging and crystallizing for 2 hours at 90 ℃ at a rotating speed of 500rpm, and fully washing the solid;
(5) Calcining the aged solid at 600 ℃ for 5 hours to dehydrate, and finally obtaining spherical or spheroidic nano ferric phosphate;
(6) Mixing and grinding the prepared nano ferric phosphate with a lithium source and glucose in a molar ratio of 2:1.03:0.3 to obtain a nano ferric phosphate lithium precursor;
sintering the prepared nano lithium iron phosphate precursor in an inert gas atmosphere, wherein the nano lithium iron phosphate precursor is prepared by the method; the sintering is performed in three sections, the first sintering temperature is 40 ℃, and the first sintering time is 1 hour; the second sintering temperature is 550 ℃, and the second sintering time is 4 hours; the third sintering temperature is 700 ℃, and the third sintering time is 8 hours; and cooling to obtain the nano-scale spherical or spheroidic lithium iron phosphate.
Fig. 3 and 4 are Scanning Electron Microscope (SEM) images of the nano-iron phosphate and nano-lithium iron phosphate cathode materials prepared in example 2, respectively. It can be seen that the particles in both figures are spherical or spheroid, with an iron phosphate particle size of 80nm and a lithium iron phosphate particle size of 150nm. The whole particles are uniformly distributed and regular in morphology, and the morphology and volume corresponding to the conversion from ferric phosphate to lithium iron phosphate are not changed excessively.
Example 3
The preparation method of the lithium iron phosphate anode material comprises the following steps:
(1) Weighing ferrous sulfate, hydrogen peroxide, sodium hydroxide, phosphoric acid and sulfuric acid, respectively dissolving in water, and preparing a ferrous sulfate solution with the concentration of 3mol/L, a hydrogen peroxide solution with the concentration of 4mol/L, a sodium hydroxide solution with the concentration of 4mol/L, a phosphoric acid solution with the concentration of 3mol/L and a sulfuric acid solution with the concentration of 3mol/L;
(2) Mixing ferrous sulfate and phosphoric acid in a ratio of 1:1 to obtain 500mL solution, adding sulfuric acid solution, adjusting pH to 2, adding excessive hydrogen peroxide solution (the molar ratio of an iron source to hydrogen peroxide is 1:0.55), and reacting for 2 hours to obtain first precursor slurry;
(3) Weighing 0.2g of citric acid, adding the citric acid into the first precursor slurry, stirring and dissolving, stirring and heating at 80 ℃ and 400rpm, dropwise adding a sodium hydroxide solution step by step, ending dropwise adding within 30min, and finally obtaining a second precursor slurry with the pH of 1.5, filtering and washing to obtain a solid;
(4) Fully washing the solid, adding a phosphoric acid solution, aging and crystallizing for 2 hours at 90 ℃ at a rotating speed of 500rpm, and fully washing the solid;
(5) Calcining the aged solid at 500 ℃ for 4 hours to dehydrate, and finally obtaining spherical or spheroidic nano ferric phosphate;
(6) Mixing and grinding the prepared nano ferric phosphate with a lithium source and glucose in a molar ratio of 2:1.03:0.3 to obtain a nano ferric phosphate lithium precursor;
sintering the prepared nano lithium iron phosphate precursor in an inert gas atmosphere, wherein: the sintering is performed in three sections, the first sintering temperature is 30 ℃, and the first sintering time is 1 hour; the second sintering temperature is 550 ℃, and the second sintering time is 4 hours; the third sintering temperature is 700 ℃, and the third sintering time is 7 hours; and cooling to obtain the nano-scale spherical or spheroidic lithium iron phosphate.
Fig. 5 and 6 are Scanning Electron Microscope (SEM) images of the nano-iron phosphate and nano-lithium iron phosphate cathode materials prepared in example 3, respectively. It can be seen that the particles in both figures are spherical or spheroid, with the iron phosphate particle size being 125nm and the lithium iron phosphate particle size being 250nm. The whole particles are uniformly distributed and regular in morphology, and the morphology and volume corresponding to the conversion from ferric phosphate to lithium iron phosphate are not changed excessively.
Comparative example 1
The preparation method of the lithium iron phosphate anode material comprises the following steps:
(1) Weighing ferrous sulfate, hydrogen peroxide, sodium hydroxide, phosphoric acid and sulfuric acid, respectively dissolving in water to prepare a ferrous sulfate solution with the concentration of 1mol/L, a hydrogen peroxide solution with the concentration of 1mol/L, a sodium hydroxide solution with the concentration of 3mol/L, a phosphoric acid solution with the concentration of 1mol/L and a sulfuric acid solution with the concentration of 1 mol/L;
(2) Mixing ferrous sulfate and phosphoric acid in a ratio of 1:1 to obtain 500mL solution, adding sulfuric acid solution, adjusting pH to 1, adding excessive hydrogen peroxide solution (the molar ratio of an iron source to hydrogen peroxide is 1:0.55), and reacting for 2 hours to obtain first precursor slurry;
(3) Stirring and heating the first precursor slurry at 80 ℃ and 400rpm, dropwise adding a sodium hydroxide solution to the first precursor slurry step by step, ending the dropwise adding within half an hour, and obtaining a solid by filtering and washing, wherein the pH value of the final solution is 1.5;
(4) Fully washing the solid, adding a phosphoric acid solution, aging and crystallizing for 2 hours at 90 ℃ at a rotating speed of 500rpm, and fully washing the solid;
(5) Calcining the aged solid at 500 ℃ for 4 hours to dehydrate, and finally obtaining nano ferric phosphate;
(6) Mixing and grinding the prepared nano ferric phosphate with a lithium source and glucose in a molar ratio of 2:1.03:0.3 to obtain a nano ferric phosphate lithium precursor;
sintering the prepared nano lithium iron phosphate precursor in an inert gas atmosphere, wherein: the sintering is performed in three sections, the first sintering temperature is 30 ℃, and the first sintering time is 1 hour; the second sintering temperature is 550 ℃, and the second sintering time is 4 hours; the third sintering temperature is 700 ℃, and the third sintering time is 7 hours; and cooling to obtain the nanoscale lithium iron phosphate.
In comparative example 1, the concentration of citric acid, which is not added as a surfactant, is different, and the spherical morphology of the material is affected, such as agglomeration, non-circular, and the like, and fig. 7 and 8 are Scanning Electron Microscope (SEM) images of the nano iron phosphate and nano lithium iron phosphate cathode materials prepared in comparative example 1, respectively. The particle size of the iron phosphate was 400nm, and the particle size of the lithium iron phosphate was 800nm. The overall particles are unevenly distributed and irregularly shaped.
TABLE 1
| Example 1 | Example 2 | Example 3 | Comparative example 1 | |
| Nanometer ferric phosphate D50 particle diameter (nm) | 1.59 | 1.43 | 1.82 | 2.13 |
| Nanometer lithium iron phosphate D50 particle diameter (nm) | 1.94 | 1.73 | 2.11 | 2.31 |
As can be seen from Table 1, the particle sizes of the lithium iron phosphate positive electrode material prepared by the preparation method provided by the invention all belong to the nanoscale range, and compared with the comparative example, the morphology difference between the lithium iron phosphate prepared by the method and the lithium iron phosphate particles is smaller, so that the morphology of the lithium iron phosphate can be regulated and controlled by the surfactant.
TABLE 2
As can be seen from table 2 above: compared with comparative example 1, the lithium iron phosphate positive electrode material particles prepared by the preparation method provided by the embodiment of the invention have larger specific surface area and extremely low resistivity, because: the lithium iron phosphate positive electrode material prepared by the embodiment of the invention has small particle size, most of the shapes are spherical or spheroid, so that the lithium iron phosphate positive electrode material has larger specific surface area, and meanwhile, the shape of the nano lithium iron phosphate particles prepared by the embodiment of the invention is regular and uniform, and further, the condition of good uniformity of carbon coating on the surfaces of the nano lithium iron phosphate particles is demonstrated, so that the resistivity of the prepared nano lithium iron phosphate positive electrode material is low, and the conductivity and the reactivity of the material are greatly improved. The electrochemical performance of the lithium ion battery can be further improved by applying the lithium ion battery to the lithium battery.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the nano ferric phosphate is characterized by comprising the following steps: preparing first precursor slurry by adopting a coprecipitation method for an iron source and a phosphorus source, adding a surfactant, adding a precipitator under the condition of stirring and heating to control the pH value to obtain second precursor slurry, and performing aftertreatment on the second precursor slurry to obtain nano ferric phosphate, wherein: the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium hexadecyl benzene sulfonate.
2. The method of manufacturing according to claim 1, comprising the steps of: adjusting the pH value of the mixed solution of the iron source and the phosphorus source to 1-2, and then carrying out coprecipitation reaction with an oxidant to obtain first precursor slurry; then uniformly mixing the first precursor slurry with a surfactant, adding a precipitant under the condition of stirring and heating to maintain the pH of the reaction at 1-2, and obtaining a second precursor slurry after the reaction is finished; and aging, washing and calcining the second precursor slurry to obtain the nano ferric phosphate.
3. The method of preparing according to claim 2, wherein the preparing of the first precursor slurry comprises: mixing an iron source solution and a phosphorus source solution to obtain a mixed solution, regulating the pH value of the mixed solution to 1-2, and then adding an excessive oxidant solution to perform coprecipitation reaction to obtain a first precursor slurry;
preferably, the iron source comprises: at least one of ferrous sulfate and iron powder, wherein the phosphorus source comprises at least one of phosphoric acid, ammonium phosphate and monoammonium phosphate, the concentration of the iron source solution is 1-3 mol/L, and the concentration of the phosphorus source solution is 1-3 mol/L;
preferably, the pH of the mixed solution is regulated to be 1-2 by utilizing sulfuric acid solution, and the concentration of the sulfuric acid solution is 1-3 mol/L;
preferably, the oxidizing agent is hydrogen peroxide, and the molar ratio of the iron source to the hydrogen peroxide is 1: (0.55-0.75), wherein the concentration of the oxidant solution is 1-4 mol/L;
preferably, the temperature of the coprecipitation reaction is 80-90 ℃ and the time is 1-3 h.
4. The method of preparing according to claim 2, wherein the preparing of the second precursor slurry comprises: uniformly mixing the first precursor slurry and a surfactant, dropwise adding a precipitator step by step under the condition of stirring and heating, and controlling the pH value of the reaction to be 1-2 to obtain the second precursor slurry;
preferably, the surfactant comprises at least one of citric acid, polyethylene glycol, cetyltrimethylammonium bromide and sodium cetylbenzenesulfonate, more preferably citric acid;
preferably, the content of the surfactant in the second precursor slurry is 0.2-1 g/500ml, the stirring speed is 400-700 rpm, and the heating temperature is 80-90 ℃;
preferably, the precipitant comprises at least one of sodium hydroxide solution and ammonia water, and the concentration of the precipitant is 1-4 mol/L;
preferably, the total dripping time of the precipitant is controlled to be 20-40 min, and the pH value of the final solution is 1-2 after the dripping of the precipitant is finished.
5. The method of preparing according to claim 2, wherein the preparing of the nano iron phosphate comprises: filtering and washing the second precursor slurry, adding a phosphoric acid solution for aging and crystallization, filtering and washing again, and calcining to obtain nano ferric phosphate;
preferably, in the aging crystallization process, the stirring rotation speed is 300-700 rpm, the heating temperature is 80-90 ℃, and the aging time is 2-4 hours;
preferably, the concentration of the phosphoric acid solution is 1-3 mol/L;
preferably, the calcination temperature is 550 to 650 ℃ and the time is 4 to 6 hours.
6. The nano iron phosphate prepared by the preparation method according to any one of claims 1 to 5, wherein the primary particle size of the nano iron phosphate is 50 to 150nm, and the morphology of the nano iron phosphate is spherical or spheroid.
7. The preparation method of the nano lithium iron phosphate anode material is characterized by comprising the following steps of: and mixing and sintering the nano ferric phosphate, a lithium source and a carbon source in an inert gas atmosphere to obtain the nano ferric phosphate lithium anode material, wherein the nano ferric phosphate is prepared by the preparation method according to any one of claims 1-5 or the nano ferric phosphate according to claim 6.
8. The preparation method of claim 7, wherein the nano-iron phosphate, the lithium source and the carbon source are mixed and ground to obtain a nano-lithium iron phosphate precursor, and then the nano-lithium iron phosphate precursor is sintered and cooled to obtain the nano-lithium iron phosphate anode material;
preferably, mixing nano ferric phosphate, a lithium source and a carbon source according to the molar ratio of (2-2.5): (1-1.50): (0.2-0.4), and then ball-milling for 4-6 hours at the rotating speed of 200-400 rpm to obtain a nano ferric phosphate lithium precursor;
preferably, the carbon source comprises at least one of glucose, sucrose, and polyacrylate;
preferably, the sintering comprises one-stage sintering, two-stage sintering and three-stage sintering, wherein the one-stage sintering is performed by adopting a first heating rate to raise the temperature from room temperature to a first sintering temperature, and the first sintering time is maintained; the second-stage sintering is to increase the temperature from the first sintering temperature to the second sintering temperature by adopting a second heating rate, and the second sintering time is kept; the third-stage sintering is to adopt a third heating rate to rise from the second sintering temperature to a third sintering temperature, and the third sintering time is kept;
more preferably, the first sintering temperature is 30 to 50 ℃, and the first sintering time period is 1 to 2 hours; the second sintering temperature is 550-600 ℃, and the second sintering time is 3-4 hours; the third sintering temperature is 700-750 ℃, and the third sintering time is 7-10 hours;
more preferably, the first heating rate is 10deg.C/min, the second heating rate is 5deg.C/min, and the third heating rate is 2deg.C/min.
9. The nano lithium iron phosphate anode material prepared by the preparation method of claim 8, wherein the primary particle size of the nano lithium iron phosphate anode material is 150-250 nm, and the morphology of the nano lithium iron phosphate anode material is spherical or spheroid.
10. A lithium ion battery comprising the nano lithium iron phosphate positive electrode material of claim 9.
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