CN117303338A - Preparation method of high-performance lithium iron phosphate positive electrode material - Google Patents
Preparation method of high-performance lithium iron phosphate positive electrode material Download PDFInfo
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- CN117303338A CN117303338A CN202311237207.6A CN202311237207A CN117303338A CN 117303338 A CN117303338 A CN 117303338A CN 202311237207 A CN202311237207 A CN 202311237207A CN 117303338 A CN117303338 A CN 117303338A
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- Prior art keywords
- iron phosphate
- lithium iron
- lithium
- source
- solid
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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 133
- 238000002360 preparation method Methods 0.000 title claims abstract description 27
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 13
- 239000002243 precursor Substances 0.000 claims abstract description 67
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 49
- 238000000498 ball milling Methods 0.000 claims abstract description 48
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 40
- 239000002002 slurry Substances 0.000 claims abstract description 38
- 239000007788 liquid Substances 0.000 claims abstract description 34
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 33
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 26
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 26
- 239000010405 anode material Substances 0.000 claims abstract description 22
- 238000001035 drying Methods 0.000 claims abstract description 22
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 20
- 239000000843 powder Substances 0.000 claims abstract description 20
- 238000005245 sintering Methods 0.000 claims abstract description 20
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 16
- 229910052742 iron Inorganic materials 0.000 claims abstract description 16
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 15
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 15
- 238000002156 mixing Methods 0.000 claims abstract description 12
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 9
- -1 iron ions Chemical class 0.000 claims abstract description 9
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 9
- 239000011574 phosphorus Substances 0.000 claims abstract description 9
- 239000012298 atmosphere Substances 0.000 claims abstract description 7
- 239000000203 mixture Substances 0.000 claims abstract description 7
- 239000008367 deionised water Substances 0.000 claims abstract description 4
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 4
- 238000007670 refining Methods 0.000 claims abstract description 3
- 238000010438 heat treatment Methods 0.000 claims description 44
- 238000000034 method Methods 0.000 claims description 25
- 239000007787 solid Substances 0.000 claims description 19
- 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 17
- 239000008103 glucose Substances 0.000 claims description 17
- 238000001354 calcination Methods 0.000 claims description 8
- 239000002245 particle Substances 0.000 claims description 8
- 230000008569 process Effects 0.000 claims description 8
- ZMANZCXQSJIPKH-UHFFFAOYSA-N Triethylamine Chemical compound CCN(CC)CC ZMANZCXQSJIPKH-UHFFFAOYSA-N 0.000 claims description 6
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical group [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 4
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 3
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 3
- MSWZFWKMSRAUBD-IVMDWMLBSA-N 2-amino-2-deoxy-D-glucopyranose Chemical compound N[C@H]1C(O)O[C@H](CO)[C@@H](O)[C@@H]1O MSWZFWKMSRAUBD-IVMDWMLBSA-N 0.000 claims description 2
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- KCXVZYZYPLLWCC-UHFFFAOYSA-N EDTA Chemical compound OC(=O)CN(CC(O)=O)CCN(CC(O)=O)CC(O)=O KCXVZYZYPLLWCC-UHFFFAOYSA-N 0.000 claims description 2
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- 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
- 235000001014 amino acid Nutrition 0.000 claims description 2
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- MSWZFWKMSRAUBD-UHFFFAOYSA-N beta-D-galactosamine Natural products NC1C(O)OC(CO)C(O)C1O MSWZFWKMSRAUBD-UHFFFAOYSA-N 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
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- 235000015165 citric acid Nutrition 0.000 claims description 2
- 235000019425 dextrin Nutrition 0.000 claims description 2
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- JDSHMPZPIAZGSV-UHFFFAOYSA-N melamine Chemical compound NC1=NC(N)=NC(N)=N1 JDSHMPZPIAZGSV-UHFFFAOYSA-N 0.000 claims description 2
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- QSNQXZYQEIKDPU-UHFFFAOYSA-N [Li].[Fe] Chemical compound [Li].[Fe] QSNQXZYQEIKDPU-UHFFFAOYSA-N 0.000 abstract description 6
- 238000009830 intercalation Methods 0.000 abstract description 3
- 230000002687 intercalation Effects 0.000 abstract description 3
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- 229930024421 Adenine Natural products 0.000 description 11
- GFFGJBXGBJISGV-UHFFFAOYSA-N Adenine Chemical compound NC1=NC=NC2=C1N=CN2 GFFGJBXGBJISGV-UHFFFAOYSA-N 0.000 description 11
- 229960000643 adenine Drugs 0.000 description 11
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- 238000004146 energy storage Methods 0.000 description 5
- 238000001027 hydrothermal synthesis Methods 0.000 description 5
- 229910010710 LiFePO Inorganic materials 0.000 description 4
- 239000011247 coating layer Substances 0.000 description 4
- 230000005012 migration Effects 0.000 description 4
- 238000013508 migration Methods 0.000 description 4
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 description 3
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
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- 239000001263 FEMA 3042 Substances 0.000 description 2
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- CKUAXEQHGKSLHN-UHFFFAOYSA-N [C].[N] Chemical compound [C].[N] CKUAXEQHGKSLHN-UHFFFAOYSA-N 0.000 description 2
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- OIRDTQYFTABQOQ-KQYNXXCUSA-N adenosine Chemical compound C1=NC=2C(N)=NC=NC=2N1[C@@H]1O[C@H](CO)[C@@H](O)[C@H]1O OIRDTQYFTABQOQ-KQYNXXCUSA-N 0.000 description 2
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- UYTPUPDQBNUYGX-UHFFFAOYSA-N guanine Chemical compound O=C1NC(N)=NC2=C1N=CN2 UYTPUPDQBNUYGX-UHFFFAOYSA-N 0.000 description 2
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- 229920002258 tannic acid Polymers 0.000 description 2
- LRBQNJMCXXYXIU-NRMVVENXSA-N tannic acid Chemical compound OC1=C(O)C(O)=CC(C(=O)OC=2C(=C(O)C=C(C=2)C(=O)OC[C@@H]2[C@H]([C@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)[C@@H](OC(=O)C=3C=C(OC(=O)C=4C=C(O)C(O)=C(O)C=4)C(O)=C(O)C=3)O2)OC(=O)C=2C=C(OC(=O)C=3C=C(O)C(O)=C(O)C=3)C(O)=C(O)C=2)O)=C1 LRBQNJMCXXYXIU-NRMVVENXSA-N 0.000 description 2
- 229940033123 tannic acid Drugs 0.000 description 2
- 235000015523 tannic acid Nutrition 0.000 description 2
- 229910001428 transition metal ion Inorganic materials 0.000 description 2
- IVIHUELQQBDVNA-UHFFFAOYSA-L C([O-])([O-])=O.[Fe+2].[Li+] Chemical compound C([O-])([O-])=O.[Fe+2].[Li+] IVIHUELQQBDVNA-UHFFFAOYSA-L 0.000 description 1
- 239000002126 C01EB10 - Adenosine Substances 0.000 description 1
- RGHNJXZEOKUKBD-SQOUGZDYSA-M D-gluconate Chemical compound OC[C@@H](O)[C@@H](O)[C@H](O)[C@@H](O)C([O-])=O RGHNJXZEOKUKBD-SQOUGZDYSA-M 0.000 description 1
- 229910013872 LiPF Inorganic materials 0.000 description 1
- 101150058243 Lipf gene Proteins 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- PFYQFCKUASLJLL-UHFFFAOYSA-N [Co].[Ni].[Li] Chemical compound [Co].[Ni].[Li] PFYQFCKUASLJLL-UHFFFAOYSA-N 0.000 description 1
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
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- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 125000004429 atom Chemical group 0.000 description 1
- 230000002238 attenuated effect Effects 0.000 description 1
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- 238000010586 diagram Methods 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- JBTWLSYIZRCDFO-UHFFFAOYSA-N ethyl methyl carbonate Chemical compound CCOC(=O)OC JBTWLSYIZRCDFO-UHFFFAOYSA-N 0.000 description 1
- 208000016253 exhaustion Diseases 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 229940050410 gluconate Drugs 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000003993 interaction Effects 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
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- 238000012986 modification Methods 0.000 description 1
- 125000004433 nitrogen atom Chemical group N* 0.000 description 1
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- 230000000750 progressive effect Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
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- 238000001228 spectrum Methods 0.000 description 1
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- 238000012876 topography Methods 0.000 description 1
- 238000005303 weighing Methods 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
- GBNDTYKAOXLLID-UHFFFAOYSA-N zirconium(4+) ion Chemical compound [Zr+4] GBNDTYKAOXLLID-UHFFFAOYSA-N 0.000 description 1
- 229910000859 α-Fe Inorganic materials 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
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B21/00—Nitrogen; Compounds thereof
- C01B21/06—Binary compounds of nitrogen with metals, with silicon, or with boron, or with carbon, i.e. nitrides; Compounds of nitrogen with more than one metal, silicon or boron
- C01B21/0605—Binary compounds of nitrogen with carbon
-
- 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention discloses a preparation method of a high-performance lithium iron phosphate positive electrode material, which comprises the following steps: adding a lithium source, an iron source and a phosphorus source into a proper amount of deionized water, uniformly mixing, and then adding a carbon source and a nitrogen source, uniformly mixing to obtain a solid-liquid mixture; ball milling and refining the obtained solid-liquid mixture to obtain lithium iron phosphate precursor slurry, and drying and granulating the slurry to obtain lithium iron phosphate precursor powder; and (3) performing high-temperature sintering on the obtained lithium iron phosphate precursor in an inert atmosphere, and obtaining the lithium iron phosphate anode material after sintering. The invention effectively promotes the rapid extraction and intercalation of lithium ions, has high electron conductivity and good conductivity, and ensures that the material shows good electrochemical performance; but also can fix iron ions and effectively inhibit the generation of iron lithium defects.
Description
Technical Field
The invention belongs to the technical field of lithium ion battery materials, and particularly relates to a preparation method of a high-performance lithium iron phosphate positive electrode material.
Background
With the rapid development of economy and the increase of population, the increasing demand for energy and the progressive exhaustion of nonrenewable sources have driven the development of new energy storage devices. The need for new chemical energy storage devices requires greater energy density, better safety, longer service life and more environmental friendliness. Among these, lithium ion batteries are rapidly growing in the market due to their numerous advantages such as high energy density, long cycle life, no memory effect, and environmental friendliness. From the initial energy storage application of small electronic instruments, the energy storage device gradually becomes a new energy source of the vehicle. The positive electrode material of the lithium ion battery has direct leading effect on the performances of the lithium ion battery in various aspects, such as energy density, circulation, multiplying power and the like.
The current main current positive electrode materials can be divided into ternary materials (nickel cobalt lithium manganate, nickel cobalt lithium aluminate), lithium-rich materials and lithium iron phosphate materials. Wherein, lithium iron phosphate LiFePO 4 The (LFP) has the advantages of high discharge specific capacity, flat and stable discharge platform, stable electrochemical performance and structure, safety, no pollution and the like, and is widely applied to the fields of new energy automobiles and energy storage. However, under room temperature conditions, liFePO 4 The lithium ion diffusion rate of the material is slow, the conductivity is low, the material can only exert higher specific capacity under the condition of low current density or high temperature, and LiFePO is limited 4 Commercial application of materials.
Thus, efforts are made to solve LiFePO during production development 4 Drawbacks of the material. Enhancement of LiFePO by modification of carbon coating 4 Properties of the material. For example, CN115893361a discloses a metal-doped carbon-coated lithium iron phosphate material, which is obtained by mixing an iron source, a phosphorus source, a lithium source and gluconate in a solvent, grinding, drying and sintering the mixture. The method improves the capacity of the material and well regulates the particle size of the material. However, the carbon layer formed by the method is easy to damage and fall off, so that the carbon layer on the surface of the lithium iron phosphate material is incompletely coated, and the conductivity of the material is further affected. Furthermore, the use of polyvinylpyrrolidone and tannic acid will increase the raw materials and the tannic acid content of the materialThe equipment cost and the practicability are not strong. CN114335480B discloses a core-shell carbon-coated doped lithium iron phosphate, carbon and transition metal ions together form a shell to coat the cathode material, so as to solve the problems of uneven and non-compact coating of the carbon layer, easy agglomeration of crystal grains, and the like. However, the method is complex to operate, the cost of the used transition metal ion raw material is high, the performance improvement is not ideal, and the method is limited to use.
LiFePO can be increased by improving the preparation method 4 Properties of the material. CN114335517B discloses a carbon composite lithium iron phosphate positive electrode material. And (3) carrying out hydrothermal synthesis reaction to obtain a carbon composite lithium iron phosphate precursor, and then roasting the carbon composite lithium iron phosphate precursor in an inert atmosphere or a reducing atmosphere to obtain the carbon composite lithium iron phosphate anode material. By a hydrothermal method, a material with uniform phase, small grain diameter and good crystallinity can be prepared, thereby leading LiFePO 4 The material has higher gram capacity and excellent multiplying power performance, and the carbon coating is more uniform and the cycle life is longer. However, due to the fact that the particle size is uniform and smaller, many gaps among the particles cannot be filled, and the compaction density of the nano lithium iron phosphate material prepared by a common hydrothermal method is low. More importantly, both hydrothermal and solvothermal processes require high pressure conditions to be completed, which increases the process complexity and safety risks of the preparation and is not suitable for large-scale production.
Doping of the material is also an improvement in LiFePO 4 A method for effectively improving the performance of the material. CN116525797a discloses a fluorine-containing lithium iron phosphate composite material, a preparation method and application thereof. The fluorine and zirconium ion co-doped anode material with excellent electrochemical performance is prepared by adopting a hydrothermal method, and the final material has the characteristics of controllable morphology and uniform particle size, and further has excellent electrochemical performance. However, the zirconium source used in this method is expensive, and the fluorine used requires high-cost production and post-treatment equipment, which greatly increases the material preparation cost, and this limits the use of this method in industrial production.
In view of the above, there is a need to provide a new method for preparing lithium iron phosphate.
Disclosure of Invention
In view of the above problems, an object of the present invention is to provide a method for preparing a high-performance lithium iron phosphate positive electrode material. Solves the problems of complex process, high cost of raw materials and environment, low production efficiency and the like in the prior art, and effectively improves the multiplying power, circulation and capacity of the lithium iron phosphate anode material.
In order to achieve the above purpose, the following technical scheme is provided:
a preparation method of a high-performance lithium iron phosphate positive electrode material comprises the following steps of;
1) Adding a lithium source, an iron source and a phosphorus source into a proper amount of deionized water, uniformly mixing, and then adding a carbon source and a nitrogen source, uniformly mixing to obtain a solid-liquid mixture;
2) Ball milling and refining the solid-liquid mixture obtained in the step 1) to obtain lithium iron phosphate precursor slurry, and drying and granulating the slurry to obtain lithium iron phosphate precursor powder;
3) And 2) calcining the lithium iron phosphate precursor obtained in the step 2) at a high temperature in an inert atmosphere, and sintering to obtain the lithium iron phosphate anode material.
Further, the lithium source in step 1) is Li 2 CO 3 、LiOH、LiNO 3 LiCl and CH 3 At least one of COOLi.
Further, the iron source in the step 1) is FeC 2 O 4 、Fe 3 (PO 4 ) 2 、FeSO 4 、Fe 2 P 2 O 7 、FeCl 3 、Fe 2 O 3 、FePO 4 、Fe 2 (SO 4 ) 3 、Fe(OH) 3 、Fe(NO 3 ) 3 、Fe(OH)(CH 3 COO) 2 、FeC 6 H 5 O 7 And Fe (Fe) 4 (P 2 O 7 ) 3 At least one of them.
Further, the phosphorus source in the step 1) is H 3 PO 4 、Fe 3 (PO 4 ) 2 、FePO 4 、(NH 4 ) 2 HPO 4 、NH 4 H 2 PO 4 、(NH 4 ) 3 PO 4 、Li 3 PO 4 And LiH 2 PO 4 At least one of them.
Further, the nitrogen source in the step 1) is at least one of urea, melamine, chitin, glucosamine, N-methyl pyrrolidone, polyvinylpyrrolidone, polyacrylonitrile, nucleobases, nucleosides, triethylamine and ethylenediamine tetraacetic acid.
Further, the carbon source in the step 1) is at least one of glucose, sucrose, fructose, soluble starch, citric acid, amino acid, dextrin and polyethylene glycol.
Further, the molar ratio of the lithium element, the phosphorus element and the iron element in the step 1) is 0.95 to 1.10:0.95 to 1.05:0.95 to 1.05, the addition of the nitrogen source accounts for 1 to 5 percent of the mass of the solid, and the addition of the carbon source accounts for 10 to 30 percent of the mass of the solid.
Further, the rotational speed of the ball milling in the step 2) is 300-1200 r/min, and the reaction time is 6-18 h.
Further, in the step 2), the drying temperature is 60-150 ℃, and the final lithium iron phosphate precursor particles D 50 ≤1μm。
Further, in the step 3), the inert atmosphere is argon or nitrogen, the calcination adopts a programmed heating mode, the temperature is firstly increased to 400-500 ℃, the heat is preserved for 1h, then the temperature is increased to 600-800 ℃, and the heat is preserved for 4-18 h.
The technical principle of the invention is as follows:
due to the olivine structure of the lithium iron phosphate, the lithium iron phosphate can only be transported in a one-dimensional transportation mode in the circulating process, and the defect of poor lithium ion diffusion capability of the lithium iron phosphate material is caused. And under high rate conditions, the lithium ions that migrate during charging cannot return to the original lithium ion positions during discharge, which results in the formation of an iron phosphate phase during cycling, leaving a large number of lithium vacancies in the material. The migration of iron ions into lithium vacancies creates iron lithium defects that ultimately impede the transport of lithium ions. As the number of cycles increases, more and more lithium iron defects are generated, deteriorating the performance of lithium iron phosphate. Thus, fixing iron ions can prevent the formation of iron lithium defects. And the migration of iron ions is closely related to the stability of ferrite bonds, and according to d-band center theory, the movement of d-band away from fermi level leads to stronger bonding action of iron atoms with surrounding atoms.
After nitrogen atoms are introduced, a carbon-nitrogen coating layer is formed on the surface of the lithium iron phosphate material, so that the d-band center of the iron atoms is subjected to principle fermi level change, the bonding effect of iron-oxygen bonds is enhanced, the effect of fixing iron ions is achieved, and the formation of iron-lithium defects caused by the migration of the iron ions in the circulation process is effectively inhibited. And the introduction of nitrogen can reduce the barrier of lithium ion diffusion, so that the lithium ions realize rapid release and intercalation actions, the material can still exert good performance under the condition of high multiplying power, and the crystal structure is kept complete.
Compared with the prior art, the invention has the following beneficial effects:
1) Compared with the traditional homogeneous carbon coating, the heterogeneous coating provided by the invention effectively improves the performance of the lithium iron phosphate material, glucose and a biological molecule nitrogen source interact in the calcining process and form a conductive network, so that the carbon-nitrogen co-doped coated lithium iron phosphate material is formed, the rapid extraction and intercalation of lithium ions can be effectively promoted, the electronic conductivity is high, the conductivity is good, and the material shows good electrochemical performance; but also can fix iron ions and effectively inhibit the generation of iron lithium defects;
2) The biomolecular nitrogen source additive used in the invention is safe and harmless, promotes the full grinding and mixing of the lithium iron phosphate material, improves the grinding efficiency, has uniform particle size distribution, and improves the distribution uniformity of the lithium iron phosphate material.
Drawings
FIG. 1 is a schematic diagram of a technical route of the present invention;
FIG. 2 is an X-ray diffraction pattern (XRD) of example 1 of the present invention;
FIG. 3 is a scanning electron microscope topography of example 1 lithium iron phosphate;
fig. 4 is a graph showing the comparison of the rate performance of button cells prepared from the lithium iron phosphate cathode materials prepared in examples 1 to 4 according to the present invention.
Detailed Description
The invention will be further described with reference to examples and figures of the accompanying drawings, to which the scope of protection of the invention is not limited.
The experimental methods in the following examples are conventional methods unless otherwise specified. The test materials used in the examples described below, unless otherwise specified, were purchased from conventional reagent stores. Unless specifically stated otherwise, technical or scientific terms used herein should be used in a common sense as understood by one of ordinary skill in the art to which this invention belongs.
The invention will be further described with reference to examples and figures of the accompanying drawings, to which the scope of protection of the invention is not limited.
The experimental methods in the following examples are conventional methods unless otherwise specified. The test materials used in the examples described below, unless otherwise specified, were purchased from conventional reagent stores.
Unless specifically stated otherwise, technical or scientific terms used herein should be used in a common sense as understood by one of ordinary skill in the art to which this invention belongs.
As shown in fig. 1, the overall technical route of the invention is as follows: accurately weighing a lithium source, an iron source, a phosphorus source, a carbon source and a nitrogen source, adding deionized water, mixing, and performing ball milling mixing treatment to obtain lithium iron phosphate precursor slurry. And drying and granulating after the water is evaporated to obtain lithium iron phosphate precursor powder. And then carrying out high-temperature sintering operation under the protection of inert gas, and obtaining the lithium iron phosphate product after cooling.
Example 1
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 1.37g of adenine in water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering the precursor material in a nitrogen atmosphere, heating the precursor material from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then heating the precursor material to 600 ℃ and preserving heat for 15h, and naturally cooling the precursor material to obtain the lithium iron phosphate anode material, wherein the crystal form and the microscopic morphology of the lithium iron phosphate anode material are shown in figures 2 and 3. XRD spectrum results show that the prepared lithium iron phosphate positive electrode material sample corresponds to the lithium iron phosphate standard card NO.77-0179 one by one, and the prepared material is pure and has no other impurities. The scanning electron microscope photo shows that the synthesized lithium iron phosphate powder has uniform particle diameter of 200-500 nanometers, can fill the gaps among materials to the maximum extent, and the materials show an olivine structure.
Example 2
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 1.37g of guanine in water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering the precursor material in a nitrogen atmosphere, heating the precursor material from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then heating the precursor material to 600 ℃ and preserving heat for 15h, and naturally cooling the precursor material to obtain the lithium iron phosphate anode material. The discharge capacity results of the subsequent fabricated button cell are shown in fig. 4. The material performance was not as good as that of example 1, but still exhibited a 2C discharge capacity of 145.54mAh/g.
Example 3
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 1.37g of adenosine in water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering the precursor material in a nitrogen atmosphere, heating the precursor material from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then heating the precursor material to 600 ℃ and preserving heat for 15h, and naturally cooling the precursor material to obtain the lithium iron phosphate anode material. The discharge capacity results of the subsequent fabricated button cell are shown in fig. 4. The material performance is obviously different under the condition of high multiplying power, and the 2C discharge capacity is 141.62mAh/g.
Example 4
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 0.57g of adenine in water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering the precursor material in a nitrogen atmosphere, heating the precursor material from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then heating the precursor material to 600 ℃ and preserving heat for 15h, and naturally cooling the precursor material to obtain the lithium iron phosphate anode material. The discharge capacity results of the subsequent fabricated button cell are shown in fig. 4. The reduction of the adding amount of the biomolecular nitrogen source greatly influences the material performance, and the capacity is attenuated at each multiplying power.
Comparative example 1
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 1.37g of adenine is placed in water and stirred uniformly, the solid-liquid ratio is 1:1, ball milling operation is carried out on the obtained solid-liquid mixed solution, the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so that lithium iron phosphate slurry is obtained;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering the precursor material in a nitrogen atmosphere, heating the precursor material from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then heating the precursor material to 600 ℃ and preserving heat for 15h, and naturally cooling the precursor material to obtain the lithium iron phosphate anode material.
Comparative example 2
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose into water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering the precursor material in a nitrogen atmosphere, heating the precursor material from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, then heating the precursor material to 600 ℃ and preserving heat for 15h, and naturally cooling the precursor material to obtain the lithium iron phosphate anode material.
Comparative example 3
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Glucose 5.69g and 5.69g of adenine is placed in water and stirred uniformly, and the solid-liquid ratio is 1:1. Performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ per minute at a heating rate of 5 ℃ per minute, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 4
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 1.37g of glucose and 1.37g of adenine are placed in water and stirred uniformly, and the solid-liquid ratio is 1:1. Performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 5
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 2.42g of glucose and 1.37g of adenine are placed in water and stirred uniformly, and the solid-liquid ratio is 1:1. Ball milling is carried out on the obtained solid-liquid mixed solution, the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so that lithium iron phosphate slurry is obtained；
(2) Putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 6
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.57g Li 2 CO 3 、30.17g FePO 4 5.69g of glucose and 1.37g of adenine are placed in water and stirred uniformly, and the solid-liquid ratio is 1:1. Performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ per minute at a heating rate of 5 ℃ per minute, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 7
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 1.37g of adenine in water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, and then heating to 750 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 8
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 1.37g of adenine in water, uniformly stirring, wherein the solid-liquid ratio is 1:1, performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 1200r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 9
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 Placing 5.69g of glucose and 1.37g of adenine in water, uniformly stirring, wherein the solid-liquid ratio is 1:3, performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 15h. And naturally cooling to obtain the lithium iron phosphate anode material.
Comparative example 10
The preparation method of the lithium iron phosphate comprises the following detailed steps:
(1) 7.76g Li 2 CO 3 、30.17g FePO 4 And 1.37g of glucose is placed in water and stirred uniformly, and the solid-liquid ratio is 1:1. Performing ball milling operation on the obtained solid-liquid mixed solution, wherein the ball-material ratio is 5:1, the ball milling time is 6h, and the ball milling rotating speed is 800r/min, so as to obtain lithium iron phosphate slurry;
(2) putting the lithium iron phosphate slurry obtained in the step (1) into an oven, drying for 8 hours at a constant temperature of 150 ℃ to remove crystal water, and then crushing and sieving the solid to obtain a yellow lithium iron phosphate powder precursor;
(3) and (3) placing the precursor material into a tube furnace, sintering under the nitrogen atmosphere, heating from room temperature to 400 ℃ at a heating rate of 5 ℃/min, preserving heat for 1h, and then heating to 600 ℃ and preserving heat for 8h. And naturally cooling to obtain the lithium iron phosphate anode material. However, the obtained positive electrode material exhibited an off-white color and the caking phenomenon was serious.
Comparative example 11
The positive electrode material used in this comparative example was purchased lithium iron phosphate powder.
The performance test method comprises the following steps:
the lithium iron phosphate materials prepared in each example and comparative example were subjected to the following electrochemical performance tests:
electrochemical testing: the lithium iron phosphate material prepared by the invention is prepared into a positive pole piece, the negative pole is a lithium piece, the diaphragm is Celgard2400, and the electrolyte is LiPF of 1mol/L 6 And mixing dimethyl carbonate and ethyl methyl carbonate (volume ratio is 1:1:1) to assemble the 2032 button cell. The preparation process of the positive pole piece comprises the following steps: mixing the anode material, the conductive agent Super P and the binder PVDF according to the mass percentage of 90:5:5, using N-methyl pyrrolidone as a solvent to prepare slurry, coating the slurry on an aluminum foil, and drying the slurry to prepare the anode pole piece. And testing the prepared button cell on a battery testing system of Shenzhen Xinwei limited company under normal temperature, wherein the charge-discharge voltage interval is 2.0-4.2V.
Lithium iron phosphate materials and other materials prepared in examples 1 to 4 and comparative examples 1 to 10 were assembled into button cells by the above-described methods for testing electrochemical properties of the button cells, and magnification conditions were set: the cycle was 8 times each at different rates of 0.2C,0.5C,1C,2C and 0.2C, resulting in capacity of the battery. The results obtained for button cells made of lithium iron phosphate materials under different conditions are shown in table 1.
TABLE 1 Performance test of lithium iron carbonate materials prepared in examples 1-4 and comparative examples 1-10
The result shows that the lithium iron phosphate material prepared by the method can exert good performance under various multiplying powers, and particularly under the condition of high multiplying power, the performance of the lithium iron phosphate material is far more than that of a lithium iron phosphate sample purchased in the market. Compared with comparative examples 1-2, the performance of the lithium iron phosphate material can be effectively improved by adding the carbon source and the biomolecular nitrogen source, and the result proves that the material performance is effectively improved compared with the traditional single homogeneous carbon coating (comparative example 2) by forming a heterogeneous coating layer to wrap the surface of the lithium iron phosphate through the interaction of glucose and alkaline biomolecules in the calcining process and forming a conductive network. In comparison of example 1 with example 4 and comparative examples 3 to 5, too much or too little nitrogen source and carbon source are added, which affects the properties of the final material: too much addition results in too thick coating layer, so that the migration path of lithium ions is too long, and the material performance is affected; and the addition of the nitrogen source and the carbon source is too small, so that a complete carbon coating layer cannot be formed, the conductivity of the material is affected, and the performance of the material is affected. Therefore, the addition amounts of the carbon source and the biomolecular nitrogen source need to be strictly controlled. Examples 1-3 demonstrate that different biomolecular nitrogen sources can affect the final material properties. By contrast, adenine can give the best material properties as a biomolecular nitrogen source. In comparison of example 1 with comparative example 6, the reasonable amount of lithium source addition also affects the performance of the final lithium iron phosphate material. The addition amount of the lithium source does not follow the molar ratio of iron to lithium of 1:1, but the lithium source is required to be excessive by 2% -5%. In comparison of example 1 with comparative examples 7 to 10, during the milling and calcining operation, it was necessary to strictly control the rotation speed and time of ball milling, the ball-material ratio, the solid content, the calcining temperature and time, so as to obtain a lithium iron phosphate material having good properties. The discharge capacity result of the subsequent button cell is shown in fig. 4, and the result shows that the material has excellent performance, and especially under the condition of high multiplying power, the discharge capacity of 2C can reach 149.68mAh/g.
Claims (10)
1. The preparation method of the high-performance lithium iron phosphate positive electrode material is characterized by comprising the following steps of;
1) Adding a lithium source, an iron source and a phosphorus source into a proper amount of deionized water, uniformly mixing, and then adding a carbon source and a nitrogen source, uniformly mixing to obtain a solid-liquid mixture;
2) Ball milling and refining the solid-liquid mixture obtained in the step 1) to obtain lithium iron phosphate precursor slurry, and drying and granulating the slurry to obtain lithium iron phosphate precursor powder;
3) And 2) calcining the lithium iron phosphate precursor obtained in the step 2) at a high temperature in an inert atmosphere, and sintering to obtain the lithium iron phosphate anode material.
2. The method according to claim 1, wherein the lithium source in step 1) is Li 2 CO 3 、LiOH、LiNO 3 LiCl and CH 3 At least one of COOLi.
3. The process according to claim 1, wherein the iron source in step 1) is FeC 2 O 4 、Fe 3 (PO 4 ) 2 、FeSO 4 、Fe 2 P 2 O 7 、FeCl 3 、Fe 2 O 3 、FePO 4 、Fe 2 (SO 4 ) 3 、Fe(OH) 3 、Fe(NO 3 ) 3 、Fe(OH)(CH 3 COO) 2 、FeC 6 H 5 O 7 And Fe (Fe) 4 (P 2 O 7 ) 3 At least one of them.
4. The process according to claim 1, wherein the phosphorus source in step 1) is H 3 PO 4 、Fe 3 (PO 4 ) 2 、FePO 4 、(NH 4 ) 2 HPO 4 、NH 4 H 2 PO 4 、(NH 4 ) 3 PO 4 、Li 3 PO 4 And LiH 2 PO 4 At least one of them.
5. The method of claim 1, wherein the nitrogen source in step 1) is at least one of urea, melamine, chitin, glucosamine, N-methylpyrrolidone, polyvinylpyrrolidone, polyacrylonitrile, nucleobases, nucleosides, triethylamine, and ethylenediamine tetraacetic acid.
6. The method of claim 1, wherein the carbon source in step 1) is at least one of glucose, sucrose, fructose, soluble starch, citric acid, amino acids, dextrin and polyethylene glycol.
7. The method according to claim 1, wherein the molar ratio of the lithium element, the phosphorus element and the iron element in the step 1) is 0.95 to 1.10:0.95 to 1.05:0.95 to 1.05, the addition of the nitrogen source accounts for 1 to 5 percent of the mass of the solid, and the addition of the carbon source accounts for 10 to 30 percent of the mass of the solid.
8. The preparation method according to claim 1, wherein the rotational speed of the ball mill in the step 2) is 300-1200 r/min and the reaction time is 6-18 h.
9. The method according to claim 1, wherein the drying temperature in step 2) is 60 to 150 ℃ and the final iron phosphateLithium precursor particle D 50 ≤1μm。
10. The preparation method of claim 1, wherein in the step 3), the inert atmosphere is argon or nitrogen, the calcination adopts a programmed heating mode, the temperature is firstly increased to 400-500 ℃, the temperature is kept for 1h, then the temperature is increased to 600-800 ℃, and the temperature is kept for 4-18 h.
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