CN117142450A - Method for preparing lithium iron phosphate anode material by taking tea polyphenol as carbon source - Google Patents
Method for preparing lithium iron phosphate anode material by taking tea polyphenol as carbon source Download PDFInfo
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- CN117142450A CN117142450A CN202311138735.6A CN202311138735A CN117142450A CN 117142450 A CN117142450 A CN 117142450A CN 202311138735 A CN202311138735 A CN 202311138735A CN 117142450 A CN117142450 A CN 117142450A
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- Prior art keywords
- lithium
- iron phosphate
- lithium iron
- tea polyphenol
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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 61
- 235000013824 polyphenols Nutrition 0.000 title claims abstract description 37
- 241001122767 Theaceae Species 0.000 title claims abstract description 35
- 150000008442 polyphenolic compounds Chemical class 0.000 title claims abstract description 35
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 32
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 32
- 238000000034 method Methods 0.000 title claims abstract description 30
- 239000010405 anode material Substances 0.000 title claims abstract description 25
- 239000000203 mixture Substances 0.000 claims abstract description 41
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000002245 particle Substances 0.000 claims abstract description 24
- 239000004576 sand Substances 0.000 claims abstract description 19
- 238000003801 milling Methods 0.000 claims abstract description 12
- 229910052742 iron Inorganic materials 0.000 claims abstract description 11
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 10
- 239000011574 phosphorus Substances 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 10
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 8
- 239000012298 atmosphere Substances 0.000 claims abstract description 7
- 238000001354 calcination Methods 0.000 claims abstract description 7
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 238000010438 heat treatment Methods 0.000 claims abstract description 7
- 239000011261 inert gas Substances 0.000 claims abstract description 7
- 238000001694 spray drying Methods 0.000 claims abstract description 7
- 238000007789 sealing Methods 0.000 claims abstract description 6
- 239000002904 solvent Substances 0.000 claims abstract description 5
- 230000032683 aging Effects 0.000 claims abstract description 3
- 239000002243 precursor Substances 0.000 claims description 31
- 239000002086 nanomaterial Substances 0.000 claims description 18
- 229910021392 nanocarbon Inorganic materials 0.000 claims description 14
- 239000000843 powder Substances 0.000 claims description 12
- 239000007774 positive electrode material Substances 0.000 claims description 11
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 10
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 7
- 239000010406 cathode material Substances 0.000 claims description 7
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 6
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 6
- 239000002994 raw material Substances 0.000 claims description 6
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 5
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 4
- 229910001448 ferrous ion Inorganic materials 0.000 claims description 4
- 229940062993 ferrous oxalate Drugs 0.000 claims description 4
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 4
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 4
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 4
- 239000004254 Ammonium phosphate Substances 0.000 claims description 3
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 3
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 3
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims description 3
- 235000019289 ammonium phosphates Nutrition 0.000 claims description 3
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 3
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 3
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 3
- 239000011790 ferrous sulphate Substances 0.000 claims description 3
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 3
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 3
- 238000006243 chemical reaction Methods 0.000 claims description 2
- INHCSSUBVCNVSK-UHFFFAOYSA-L lithium sulfate Inorganic materials [Li+].[Li+].[O-]S([O-])(=O)=O INHCSSUBVCNVSK-UHFFFAOYSA-L 0.000 claims description 2
- 239000007787 solid Substances 0.000 claims description 2
- RBTVSNLYYIMMKS-UHFFFAOYSA-N tert-butyl 3-aminoazetidine-1-carboxylate;hydrochloride Chemical compound Cl.CC(C)(C)OC(=O)N1CC(N)C1 RBTVSNLYYIMMKS-UHFFFAOYSA-N 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 13
- 239000011164 primary particle Substances 0.000 abstract description 7
- 230000000694 effects Effects 0.000 abstract description 3
- 238000009776 industrial production Methods 0.000 abstract description 3
- 230000000536 complexating effect Effects 0.000 abstract description 2
- 230000006872 improvement Effects 0.000 abstract description 2
- 229910021645 metal ion Inorganic materials 0.000 abstract description 2
- ISWSIDIOOBJBQZ-UHFFFAOYSA-N phenol group Chemical group C1(=CC=CC=C1)O ISWSIDIOOBJBQZ-UHFFFAOYSA-N 0.000 abstract description 2
- 230000008569 process Effects 0.000 abstract description 2
- 238000005245 sintering Methods 0.000 abstract description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 description 9
- 239000000047 product Substances 0.000 description 7
- 230000000052 comparative effect Effects 0.000 description 5
- 238000010532 solid phase synthesis reaction Methods 0.000 description 5
- 238000001027 hydrothermal synthesis Methods 0.000 description 4
- 230000003647 oxidation Effects 0.000 description 4
- 238000007254 oxidation reaction Methods 0.000 description 4
- 239000012071 phase Substances 0.000 description 4
- 238000003980 solgel method Methods 0.000 description 4
- 239000013078 crystal Substances 0.000 description 3
- 238000002360 preparation method Methods 0.000 description 3
- 239000003963 antioxidant agent Substances 0.000 description 2
- 239000011248 coating agent Substances 0.000 description 2
- 238000000576 coating method Methods 0.000 description 2
- 239000002131 composite material Substances 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 230000018109 developmental process Effects 0.000 description 2
- 230000005496 eutectics Effects 0.000 description 2
- 239000007788 liquid Substances 0.000 description 2
- 239000007791 liquid phase Substances 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000001878 scanning electron micrograph Methods 0.000 description 2
- 238000001308 synthesis method Methods 0.000 description 2
- QJZYHAIUNVAGQP-UHFFFAOYSA-N 3-nitrobicyclo[2.2.1]hept-5-ene-2,3-dicarboxylic acid Chemical compound C1C2C=CC1C(C(=O)O)C2(C(O)=O)[N+]([O-])=O QJZYHAIUNVAGQP-UHFFFAOYSA-N 0.000 description 1
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 1
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 238000002441 X-ray diffraction Methods 0.000 description 1
- 230000003078 antioxidant effect Effects 0.000 description 1
- 239000010426 asphalt Substances 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 238000000498 ball milling Methods 0.000 description 1
- 230000008901 benefit Effects 0.000 description 1
- 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 1
- 239000007795 chemical reaction product Substances 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- OPQARKPSCNTWTJ-UHFFFAOYSA-L copper(ii) acetate Chemical compound [Cu+2].CC([O-])=O.CC([O-])=O OPQARKPSCNTWTJ-UHFFFAOYSA-L 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 239000012530 fluid Substances 0.000 description 1
- 239000008103 glucose Substances 0.000 description 1
- 238000009775 high-speed stirring Methods 0.000 description 1
- 239000004021 humic acid Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 238000002156 mixing Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000012299 nitrogen atmosphere Substances 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000003208 petroleum Substances 0.000 description 1
- ZNNZYHKDIALBAK-UHFFFAOYSA-M potassium thiocyanate Chemical compound [K+].[S-]C#N ZNNZYHKDIALBAK-UHFFFAOYSA-M 0.000 description 1
- 229940116357 potassium thiocyanate Drugs 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 239000007858 starting material Substances 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 238000012546 transfer Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—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
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Organic Chemistry (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention provides a method for preparing a lithium iron phosphate anode material by taking tea polyphenol as a carbon source, which comprises the following steps of (1) adding an iron source, a lithium source, a phosphorus source and the tea polyphenol into a solvent, and uniformly stirring; (2) sealing, standing and aging; (3) adding the mixture into a sand mill for sand milling; (4) forming a gel solution; (5) spray drying; (6) Transferring into a heating furnace, keeping the temperature at 600-800 ℃ for 5-12 h in an inert gas protection atmosphere, calcining at the constant temperature, and cooling to the normal temperature within 5-10 h to obtain the lithium iron phosphate anode material. The complexing effect of the tea polyphenol and the metal ions is utilized, so that the materials are mixed more uniformly, the sanding time is shortened, the phenolic structure of the tea polyphenol can further inhibit primary particle growth during sintering, and the particle size is controlled; the multiplying power performance of the lithium iron phosphate anode material prepared by the method is improved, and the lithium iron phosphate anode material has great reference effect on the process improvement in industrial production.
Description
Technical Field
The invention belongs to the field of lithium ion batteries, and particularly relates to a method for preparing a lithium iron phosphate anode material by taking tea polyphenol as a carbon source.
Background
In the high-speed growth period of new energy industry, the lithium iron phosphate material becomes an indispensable part of the battery anode material by virtue of the cost performance advantage, and the global strong demand for lithium iron phosphate in the next few years is predicted. At present, the key to restrict the development of the lithium iron phosphate battery is that on the lithium iron phosphate positive electrode material, the low electric conductivity of electrons and ions is two fatal defects to restrict the development of the lithium iron phosphate positive electrode material, and the low electric conductivity also causes the reduction of multiplying power and cycle performance. Among the methods for improving these problems, carbon coating treatment of the surface of the positive electrode material is currently the most widely used and economically viable method.
Currently, the preparation of lithium iron phosphate has two main types, namely a solid-phase synthesis method and a liquid-phase synthesis method, wherein the liquid-phase synthesis method comprises a hydrothermal method, coprecipitation and the like, a sol-gel method and the like. In order to mix the starting materials at the molecular level and obtain a more uniform precursor, the industrialization is more difficult than the solid phase synthesis method due to the higher requirements for control of the production conditions. In contrast, the solid phase method has uneven raw materials, larger particles of chemical reaction products and wide particle size distribution range.
In addition, when the lithium iron phosphate positive electrode material is used for manufacturing a lithium ion battery, the requirements on purity, crystal phase, impurities and the like are very strict. When the oxidation degree of ferrous iron in the lithium iron phosphate reaches 1%, the specific capacity can be reduced by more than 30%. The purity of the lithium iron phosphate anode material is improved, the oxidation of ferrous iron is prevented, and the performance of the lithium iron phosphate anode material can be improved.
The Chinese patent No. 102249209A discloses a preparation method of pure crystal phase nano lithium iron phosphate particles, which adopts a continuous supercritical (subcritical) hydrothermal synthesis technology, utilizes the rapid mass transfer and crystallization principles of supercritical (subcritical) fluid to prepare nano LiFePO4 particles, and prepares an electrode material with stable performance by adding water-soluble antioxidants (such as tea polyphenol and the like) into raw material liquid. The Chinese patent No. 107994229A is characterized in that firstly, petroleum asphalt is used as a carbon source to prepare nano carbon in air, then the nano carbon is subjected to shrinkage deformation in a nitrogen atmosphere to obtain nano carbon spheres with high specific capacity, then the nano carbon spheres, tea polyphenol, a phosphorus source, a lithium source and an iron source are mixed, a eutectic precursor is prepared by a hydrothermal method, and finally, the eutectic precursor, glucose, copper acetate, potassium thiocyanate and humic acid are mixed, ground and calcined to prepare the novel lithium iron phosphate anode material. The carbon source adopts a hydrothermal synthesis method, tea polyphenol is added as an antioxidant, ferrous iron oxidation is prevented, low purity of a product crystal phase is avoided, and the electrical property stability of the lithium iron phosphate anode material is improved.
Disclosure of Invention
Aiming at the defects of the prior art, the invention provides a method for preparing a lithium iron phosphate anode material by combining a sol-gel method with a solid phase method, which is suitable for industrial production, and adopts tea polyphenol as a carbon source, so that the materials can be mixed more uniformly, and the sanding time is shortened; meanwhile, the grain size growth is inhibited to a certain extent, and the grain size is controlled.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the invention firstly provides a method for preparing a lithium iron phosphate anode material by taking tea polyphenol as a carbon source, which comprises the following steps:
(1) Preparing a precursor mixture: adding an iron source, a lithium source, a phosphorus source, tea polyphenol and a solvent for preparing a lithium iron phosphate raw material into a reaction container, and uniformly stirring;
(2) Sealing, standing and aging the precursor mixture;
(3) Adding the precursor mixture after standing into a sand mill for sand milling to obtain a nano material mixture;
(4) Adding nano carbon sol into the nano material mixture, and stirring at a high speed to obtain a gel solution;
(5) Spray drying the gel solution mixture to obtain precursor powder;
(6) And (3) transferring the precursor powder obtained in the step (5) into a heating furnace, keeping the temperature at 600-800 ℃ for 5-12 h in an inert gas protection atmosphere, calcining at the constant temperature, and cooling to the normal temperature within 5-10 h to obtain the lithium iron phosphate anode material.
Specifically, the iron source is a ferrous ion iron source and is one or a combination of more than two of ferrous oxalate, ferrous sulfate or ferrous oxide;
specifically, the lithium source is one or more than two of lithium dihydrogen phosphate, lithium carbonate, lithium nitrate, lithium hydroxide, lithium acetate or lithium sulfate;
specifically, the phosphorus source is one or a combination of more than two of lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or ammonium phosphate.
Preferably, in the step (1), the molar ratio of the iron element, the phosphorus element and the lithium element of the iron source, the phosphorus source and the lithium source is (0.90-1.00): (0.95-1.05): (1.00-1.10), and the mass fraction of the tea polyphenol in the solid raw material is 1.5-5wt%. Preferably, the solvent in the step (1) is deionized water, or absolute ethyl alcohol, or a mixture of deionized water and absolute ethyl alcohol. Preferably, the standing time used in the step (2) is at least 8 hours, and the standing temperature is 25+/-5 ℃.
Preferably, the sand milling time used in the step (3) is more than 30min, and the particle size D50 of the obtained sol-gel mixture is 100-500 nm.
Preferably, the nano carbon sol in the step (4) is added in an amount of 0.1 to 2 percent by weight of the nano material mixture;
preferably, the rotating speed of the high-speed stirring is 800-1600 rpm;
preferably, the air inlet temperature used in the step (5) is 100-280 ℃; the exhaust temperature is 50-80 ℃.
The invention also provides the lithium iron phosphate anode material prepared by the method, and the addition amount of tea polyphenol is controlled to enable the mass fraction of carbon in the lithium iron phosphate anode material to be 1-3%.
Compared with the prior art, the invention has the following outstanding effects:
the invention provides a method for preparing a lithium iron phosphate anode material by adopting tea polyphenol as a carbon source through a method of combining a sol-gel method with a solid phase method, wherein the complexing effect of the tea polyphenol and metal ions is utilized, the sol-gel method is adopted to mix materials more uniformly after standing, the sanding time is shortened, the phenolic structure of the tea polyphenol can further inhibit primary particle growth during sintering, and the particle size is controlled; in addition, the strong reducibility of the tea polyphenol can prevent ferrous ions in an iron source from being oxidized in the ball milling or sand milling process, and can also solve the problem that the oxidation degree of the ferrous ions is influenced by dissolved oxygen in water when a water system is used for mixing materials. According to the invention, the carbon sol is added, so that on one hand, the conductivity of the lithium iron phosphate material can be improved, and on the other hand, the added carbon sol can form a coating on the surface of the lithium iron phosphate, so that the stability of the lithium iron phosphate is improved, and the lithium iron phosphate material has better electrochemical performance. The multiplying power performance of the lithium iron phosphate anode material prepared by the method is improved, other physical and chemical properties are also obviously improved, and the lithium iron phosphate anode material has great reference effect on the process improvement in industrial production.
Drawings
Fig. 1 is an SEM image of example 1 of the present invention.
Figure 2 is an XRD pattern of examples and comparative examples of the present invention.
FIG. 3 is a graph of specific discharge capacity at 0.5C for examples and comparative examples of the present invention.
Detailed Description
The present invention will be described in detail with reference to specific examples. The following examples will assist those skilled in the art in further understanding the present invention, but are not intended to limit the invention in any way. It should be noted that variations and modifications could be made by those skilled in the art without departing from the inventive concept. These are all within the scope of the present invention.
Example 1
The method for preparing the lithium iron phosphate positive electrode material by using tea polyphenol as a carbon source comprises the following steps of:
(1) Preparing a precursor mixture: 150ml of 4.75g of ferrous oxalate, 3.64g of lithium dihydrogen phosphate and 0.20g of tea polyphenol were added
Stirring in a mixed liquid of deionized water and 60ml of absolute ethyl alcohol for 2 hours;
(2) Sealing and standing the precursor mixture for 8 hours at normal temperature;
(3) And (3) adding the precursor mixture after standing into a sand mill for sand milling, and measuring the particle size every 10 minutes after sand milling for 20 minutes. Stopping sanding after 40min, wherein the particle size D50 of the material is 235nm, and obtaining a nano material mixture;
(4) Adding nano carbon sol (the addition amount is 1wt% of the nano material mixture) into the nano material mixture, and stirring at 1200rpm to obtain a gel solution;
(5) Spray drying the gel solution, and controlling the air inlet temperature to be 100 ℃; the exhaust temperature is 50 ℃ to obtain precursor powder;
(6) Transferring the precursor powder obtained in the step (5) into a heating furnace, keeping the temperature at 600-800 ℃ for 6 hours in an inert gas protection atmosphere, calcining at the constant temperature, and cooling to the normal temperature within 6 hours to obtain the lithium iron phosphate anode material with the carbon content of 1.58%.
The SEM image, XRD result and electrochemical properties of the lithium iron phosphate/carbon composite material prepared by the preparation method of this example are shown in fig. 1, 2 and 3, respectively. As can be seen from the SEM in fig. 1, the primary particle size of the lithium iron phosphate product produced in example 1 is small, and the D50 particle size is 200nm. From the diffraction peak positions, intensities and widths in fig. 2, it can be deduced that the synthesized product is a pure phase of lithium iron phosphate and also has good crystallinity, and the synthesized lithium iron phosphate/carbon composite material has very excellent electrochemical properties, see fig. 3.
Example 2
The method for preparing the lithium iron phosphate positive electrode material by using tea polyphenol as a carbon source comprises the following steps of:
(1) Preparing a precursor mixture: 5.00g of ferrous sulfate, 4.00g of diammonium hydrogen phosphate, 1.29g of lithium carbonate and 0.2g of tea polyphenol are added into 200ml of deionized water and stirred for 2 hours;
(2) Sealing and standing the precursor mixture for 12 hours at normal temperature;
(3) And (3) adding the precursor mixture after standing into a sand mill for sand milling, and measuring the particle size every 10 minutes after sand milling for 20 minutes. Stopping sanding after 40min, wherein the particle size D50 of the material is 276nm, and the nano material mixture;
(4) Adding nano carbon sol (the addition amount is 1wt% of the nano material mixture) into the nano material mixture, and stirring at 1200rpm to obtain a gel solution;
(5) Spray drying the gel solution, and controlling the air inlet temperature to be 150 ℃; the exhaust temperature is 80 ℃ to obtain precursor powder;
(6) Transferring the precursor powder obtained in the step (5) into a heating furnace, keeping the temperature at 600-800 ℃ for 8 hours in an inert gas protection atmosphere, calcining at the constant temperature, and then cooling to the normal temperature within 6 hours to obtain the lithium iron phosphate positive electrode material, wherein the primary particle size of the generated lithium iron phosphate product is small, the D50 particle size is about 120nm, and the carbon content is 1.66%.
Example 3
The method for preparing the lithium iron phosphate positive electrode material by using tea polyphenol as a carbon source comprises the following steps of:
(1) Preparing a precursor mixture: 2.37g of ferrous oxide, 5.22g of ammonium phosphate, 2.31g of lithium acetate and 0.2g of tea polyphenol are added into 250ml of deionized water and stirred for 2 hours;
(2) Sealing and standing the precursor mixture for 8 hours at normal temperature;
(3) And (3) adding the precursor mixture after standing into a sand mill for sand milling, and measuring the particle size every 10 minutes after sand milling for 20 minutes. Stopping sanding after 40min, wherein the particle size D50 of the material is 228nm, and the nano material mixture;
(4) Adding nano carbon sol (the addition amount is 1wt% of the nano material mixture) into the nano material mixture, and stirring at 1200rpm to obtain a gel solution;
(5) Spray drying the gel solution, and controlling the air inlet temperature to be 280 ℃; the exhaust temperature is 60 ℃ to obtain precursor powder;
(6) Transferring the precursor powder obtained in the step (5) into a heating furnace, keeping the temperature at 600-800 ℃ for 8 hours in an inert gas protection atmosphere, calcining at the constant temperature, and then cooling to the normal temperature within 6 hours to obtain the lithium iron phosphate positive electrode material, wherein the primary particle size of the generated lithium iron phosphate product is small, the D50 particle size is about 100nm, and the carbon content is 1.71%.
Example 4
The nanocarbon sol added in step (4) of this example is 0.1wt% of the nanomaterial mixture; other characteristics are the same as in example 1, and the primary particle size of the produced lithium iron phosphate product is small, and the D50 particle size is about 240 nm.
Example 5
The nano carbon sol added in the step (4) of the embodiment is 2wt% of the nano material mixture; other characteristics are the same as in example 1, and the primary particle size of the produced lithium iron phosphate product is small, and the D50 particle size is about 250 nm.
Comparative example
The method for preparing the lithium iron phosphate positive electrode material by using citric acid as a carbon source comprises the following steps of:
preparing a precursor mixture: 4.75g of ferrous oxalate, 4.00g of ammonium dihydrogen phosphate, 2.31g of lithium acetate, 0.61g of citric acid and 250ml of deionized water are added into a sand mill to be sanded, and after 20 minutes of sanding, the particle size is measured every 10 minutes. Stopping sanding after 1h and 20min, wherein the particle size D50 of the material is 293nm, and the nano material is a mixture;
adding 0.2g of nano carbon sol into the nano material mixture, and stirring at a high speed to obtain a gel solution;
spray drying the gel solution, and controlling the air inlet temperature to be 280 ℃; the exhaust temperature is 60 ℃ to obtain precursor powder;
transferring the precursor powder obtained in the step (3) into a heating furnace, keeping the temperature at 600-800 ℃ for 8 hours in an inert gas protection atmosphere, calcining at the constant temperature, and cooling to the normal temperature within 6 hours to obtain the lithium iron phosphate anode material, wherein the D50 particle size is about 280nm, and the carbon content is 1.70%. It is obvious that the comparative example uses citric acid as the carbon source, the sanding time is longer, and the material particle diameter D50 is still longer than that of the implementation
The particle size D50 of the material using tea polyphenols in examples 1-3 was much larger; in addition, as can be seen from fig. 3, the specific capacities of examples 1, 4, and 5 are all better than those of the comparative examples.
Specific capacity test results of the lithium iron phosphate cathode materials prepared in the present examples 4 and 5 are shown in the following table:
Claims (8)
1. the method for preparing the lithium iron phosphate anode material by taking tea polyphenol as a carbon source is characterized by comprising the following steps of:
(1) Preparing a precursor mixture: adding an iron source, a lithium source, a phosphorus source, tea polyphenol and a solvent for preparing a lithium iron phosphate raw material into a reaction container, and uniformly stirring;
(2) Sealing, standing and aging the precursor mixture;
(3) Adding the precursor mixture after standing into a sand mill for sand milling to obtain a nano material mixture;
(4) Adding nano carbon sol into the nano material mixture, and stirring at a high speed to obtain a gel solution;
(5) Spray drying the gel solution to obtain precursor powder;
(6) And (3) transferring the precursor powder obtained in the step (5) into a heating furnace, keeping the temperature at 600-800 ℃ for 5-12 h in an inert gas protection atmosphere, calcining at the constant temperature, and cooling to the normal temperature within 5-10 h to obtain the lithium iron phosphate anode material.
2. The method for preparing the lithium iron phosphate cathode material by taking tea polyphenol as a carbon source according to claim 1, which is characterized in that: the iron source is a ferrous ion iron source and is one or a combination of more than two of ferrous oxalate, ferrous sulfate or ferrous oxide; the lithium source is one or a combination of more than two of lithium dihydrogen phosphate, lithium carbonate, lithium nitrate, lithium hydroxide, lithium acetate or lithium sulfate; the phosphorus source is one or more than two of lithium dihydrogen phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or ammonium phosphate.
3. The method for preparing the lithium iron phosphate cathode material by taking tea polyphenol as a carbon source according to claim 1, which is characterized in that: in the step (1), the molar ratio of the iron element, the phosphorus element and the lithium element of the iron source, the phosphorus source and the lithium source is (0.90-1.00): (0.95-1.05): (1.00-1.10), the adding amount of the tea polyphenol in the solid raw material is 1.5-5wt%, and the adding amount of the nano carbon sol is 0.1-2% wt of the nano mixture.
4. The method for preparing the lithium iron phosphate cathode material by taking tea polyphenol as a carbon source according to claim 1, which is characterized in that: the solvent in the step (1) is deionized water, absolute ethyl alcohol or a mixture of deionized water and absolute ethyl alcohol.
5. The method for preparing the lithium iron phosphate cathode material by taking tea polyphenol as a carbon source according to claim 1, which is characterized in that: the standing time used in the step (2) is at least 8 hours, and the standing temperature is 25+/-5 ℃.
6. The method for preparing the lithium iron phosphate cathode material by taking tea polyphenol as a carbon source according to claim 1, which is characterized in that: the sand milling time used in the step (3) is more than 30min, and the particle size D50 of the obtained sol-gel mixture is 100-500 nm.
7. The method for preparing the lithium iron phosphate cathode material by taking tea polyphenol as a carbon source according to claim 1, which is characterized in that: the air inlet temperature used in the step (4) is 100-280 ℃; the exhaust temperature is 50-80 ℃.
8. A lithium iron phosphate positive electrode material prepared by the method of any one of claims 1 to 7, characterized in that: the mass fraction of carbon in the lithium iron phosphate anode material is 1-3%.
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