CN116598442A - Lithium iron manganese phosphate coated ternary composite material and preparation method and application thereof - Google Patents
Lithium iron manganese phosphate coated ternary composite material and preparation method and application thereof Download PDFInfo
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- CN116598442A CN116598442A CN202310328829.3A CN202310328829A CN116598442A CN 116598442 A CN116598442 A CN 116598442A CN 202310328829 A CN202310328829 A CN 202310328829A CN 116598442 A CN116598442 A CN 116598442A
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- Prior art keywords
- ternary
- lithium iron
- source
- manganese phosphate
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- DVATZODUVBMYHN-UHFFFAOYSA-K lithium;iron(2+);manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[Fe+2].[O-]P([O-])([O-])=O DVATZODUVBMYHN-UHFFFAOYSA-K 0.000 title claims abstract description 135
- 239000011206 ternary composite Substances 0.000 title claims abstract description 27
- 238000002360 preparation method Methods 0.000 title claims abstract description 14
- 229910052692 Dysprosium Inorganic materials 0.000 claims abstract description 57
- KBQHZAAAGSGFKK-UHFFFAOYSA-N dysprosium atom Chemical compound [Dy] KBQHZAAAGSGFKK-UHFFFAOYSA-N 0.000 claims abstract description 57
- 239000011247 coating layer Substances 0.000 claims abstract description 44
- 239000002131 composite material Substances 0.000 claims abstract description 28
- 239000002243 precursor Substances 0.000 claims description 82
- 238000005245 sintering Methods 0.000 claims description 48
- 239000000243 solution Substances 0.000 claims description 46
- 238000002156 mixing Methods 0.000 claims description 38
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims description 38
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 33
- 239000011572 manganese Substances 0.000 claims description 31
- 238000000034 method Methods 0.000 claims description 30
- 229910052748 manganese Inorganic materials 0.000 claims description 29
- PWHULOQIROXLJO-UHFFFAOYSA-N Manganese Chemical compound [Mn] PWHULOQIROXLJO-UHFFFAOYSA-N 0.000 claims description 21
- 239000012298 atmosphere Substances 0.000 claims description 20
- 235000010288 sodium nitrite Nutrition 0.000 claims description 19
- QXPQVUQBEBHHQP-UHFFFAOYSA-N 5,6,7,8-tetrahydro-[1]benzothiolo[2,3-d]pyrimidin-4-amine Chemical compound C1CCCC2=C1SC1=C2C(N)=NC=N1 QXPQVUQBEBHHQP-UHFFFAOYSA-N 0.000 claims description 16
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 claims description 15
- 238000003756 stirring Methods 0.000 claims description 15
- 229910052759 nickel Inorganic materials 0.000 claims description 14
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 13
- 239000010941 cobalt Substances 0.000 claims description 13
- 229910017052 cobalt Inorganic materials 0.000 claims description 13
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 13
- 239000000203 mixture Substances 0.000 claims description 12
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims description 10
- KFDQGLPGKXUTMZ-UHFFFAOYSA-N [Mn].[Co].[Ni] Chemical compound [Mn].[Co].[Ni] KFDQGLPGKXUTMZ-UHFFFAOYSA-N 0.000 claims description 10
- 238000001354 calcination Methods 0.000 claims description 10
- 238000006243 chemical reaction Methods 0.000 claims description 10
- 238000000975 co-precipitation Methods 0.000 claims description 10
- 229910052744 lithium Inorganic materials 0.000 claims description 10
- 229910052760 oxygen Inorganic materials 0.000 claims description 10
- 239000002244 precipitate Substances 0.000 claims description 10
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 8
- 238000001035 drying Methods 0.000 claims description 8
- 238000000227 grinding Methods 0.000 claims description 8
- 229910001416 lithium ion Inorganic materials 0.000 claims description 8
- 229910052698 phosphorus Inorganic materials 0.000 claims description 8
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 claims description 7
- 239000001301 oxygen Substances 0.000 claims description 7
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 7
- 239000012670 alkaline solution Substances 0.000 claims description 6
- 229910052742 iron Inorganic materials 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 5
- 239000011574 phosphorus Substances 0.000 claims description 5
- 239000002994 raw material Substances 0.000 claims description 5
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 4
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 4
- 239000010406 cathode material Substances 0.000 claims description 3
- 239000011248 coating agent Substances 0.000 claims description 3
- 238000000576 coating method Methods 0.000 claims description 3
- 239000001267 polyvinylpyrrolidone Substances 0.000 claims description 3
- 235000013855 polyvinylpyrrolidone Nutrition 0.000 claims description 3
- 229920000036 polyvinylpyrrolidone Polymers 0.000 claims description 3
- LCPVQAHEFVXVKT-UHFFFAOYSA-N 2-(2,4-difluorophenoxy)pyridin-3-amine Chemical compound NC1=CC=CN=C1OC1=CC=C(F)C=C1F LCPVQAHEFVXVKT-UHFFFAOYSA-N 0.000 claims description 2
- FLWXWKDFOLALOB-UHFFFAOYSA-H dysprosium(3+);trisulfate Chemical compound [Dy+3].[Dy+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O FLWXWKDFOLALOB-UHFFFAOYSA-H 0.000 claims description 2
- -1 nickel cobalt aluminum Chemical compound 0.000 claims description 2
- CHQMHPLRPQMAMX-UHFFFAOYSA-L sodium persulfate Substances [Na+].[Na+].[O-]S(=O)(=O)OOS([O-])(=O)=O CHQMHPLRPQMAMX-UHFFFAOYSA-L 0.000 claims description 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 238000003801 milling Methods 0.000 claims 1
- 229910052761 rare earth metal Inorganic materials 0.000 abstract description 8
- 150000002910 rare earth metals Chemical class 0.000 abstract description 8
- 239000000463 material Substances 0.000 description 23
- 239000007774 positive electrode material Substances 0.000 description 14
- 230000000052 comparative effect Effects 0.000 description 10
- 239000000843 powder Substances 0.000 description 9
- 239000002002 slurry Substances 0.000 description 9
- 239000012266 salt solution Substances 0.000 description 8
- 238000012360 testing method Methods 0.000 description 8
- 239000001257 hydrogen Substances 0.000 description 7
- 229910052739 hydrogen Inorganic materials 0.000 description 7
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 description 5
- 229910052808 lithium carbonate Inorganic materials 0.000 description 5
- UFHFLCQGNIYNRP-UHFFFAOYSA-N Hydrogen Chemical compound [H][H] UFHFLCQGNIYNRP-UHFFFAOYSA-N 0.000 description 4
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 3
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 description 3
- 235000011114 ammonium hydroxide Nutrition 0.000 description 3
- 239000013078 crystal Substances 0.000 description 3
- 239000008367 deionised water Substances 0.000 description 3
- 229910021641 deionized water Inorganic materials 0.000 description 3
- 238000001914 filtration Methods 0.000 description 3
- 239000007789 gas Substances 0.000 description 3
- 230000014759 maintenance of location Effects 0.000 description 3
- 229910017604 nitric acid Inorganic materials 0.000 description 3
- 239000012299 nitrogen atmosphere Substances 0.000 description 3
- 239000004576 sand Substances 0.000 description 3
- 238000002791 soaking Methods 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- 238000005303 weighing Methods 0.000 description 3
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 description 2
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- OIFBSDVPJOWBCH-UHFFFAOYSA-N Diethyl carbonate Chemical compound CCOC(=O)OCC OIFBSDVPJOWBCH-UHFFFAOYSA-N 0.000 description 2
- KMTRUDSVKNLOMY-UHFFFAOYSA-N Ethylene carbonate Chemical compound O=C1OCCO1 KMTRUDSVKNLOMY-UHFFFAOYSA-N 0.000 description 2
- 239000002033 PVDF binder Substances 0.000 description 2
- CEBNZLKRYBQXSF-UHFFFAOYSA-E [Li+].[Fe+2].P(=O)([O-])([O-])[O-].[Mn+2].[C+4].P(=O)([O-])([O-])[O-].P(=O)([O-])([O-])[O-] Chemical compound [Li+].[Fe+2].P(=O)([O-])([O-])[O-].[Mn+2].[C+4].P(=O)([O-])([O-])[O-].P(=O)([O-])([O-])[O-] CEBNZLKRYBQXSF-UHFFFAOYSA-E 0.000 description 2
- 239000003575 carbonaceous material Substances 0.000 description 2
- 238000009831 deintercalation Methods 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 238000010828 elution Methods 0.000 description 2
- 229910021389 graphene Inorganic materials 0.000 description 2
- 238000000265 homogenisation Methods 0.000 description 2
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 description 2
- 229910001437 manganese ion Inorganic materials 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 2
- 230000000087 stabilizing effect Effects 0.000 description 2
- 238000003860 storage Methods 0.000 description 2
- 230000005536 Jahn Teller effect Effects 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- 239000006230 acetylene black Substances 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- 229910021529 ammonia Inorganic materials 0.000 description 1
- 238000004458 analytical method Methods 0.000 description 1
- 229910052786 argon Inorganic materials 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000005520 cutting process Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 230000008021 deposition Effects 0.000 description 1
- IEJIGPNLZYLLBP-UHFFFAOYSA-N dimethyl carbonate Chemical compound COC(=O)OC IEJIGPNLZYLLBP-UHFFFAOYSA-N 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000000840 electrochemical analysis Methods 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000011065 in-situ storage Methods 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 239000010410 layer Substances 0.000 description 1
- 239000012982 microporous membrane Substances 0.000 description 1
- 239000012046 mixed solvent Substances 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000010287 polarization Effects 0.000 description 1
- 229920000098 polyolefin Polymers 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
Classifications
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- 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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- 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
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/40—Nickelates
- C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01G—COMPOUNDS CONTAINING METALS NOT COVERED BY SUBCLASSES C01D OR C01F
- C01G53/00—Compounds of nickel
- C01G53/40—Nickelates
- C01G53/42—Nickelates containing alkali metals, e.g. LiNiO2
- C01G53/44—Nickelates containing alkali metals, e.g. LiNiO2 containing manganese
-
- 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
- H01M4/04—Processes of manufacture in general
- H01M4/0471—Processes of manufacture in general involving thermal treatment, e.g. firing, sintering, backing particulate active material, thermal decomposition, pyrolysis
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/485—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of mixed oxides or hydroxides for inserting or intercalating light metals, e.g. LiTi2O4 or LiTi2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/50—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese
- H01M4/505—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of manganese of mixed oxides or hydroxides containing manganese for inserting or intercalating light metals, e.g. LiMn2O4 or LiMn2OxFy
-
- 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
- H01M4/48—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides
- H01M4/52—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron
- H01M4/525—Selection of substances as active materials, active masses, active liquids of inorganic oxides or hydroxides of nickel, cobalt or iron of mixed oxides or hydroxides containing iron, cobalt or nickel for inserting or intercalating light metals, e.g. LiNiO2, LiCoO2 or LiCoOxFy
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- 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
- H01M4/626—Metals
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- 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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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- 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
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
Abstract
The invention provides a lithium iron manganese phosphate coated ternary composite material, a preparation method and application thereof, wherein the composite material comprises a ternary core and a lithium iron manganese phosphate coating layer coated on the surface of the core; dysprosium elements are doped in the ternary core and the lithium iron manganese phosphate coating layer. The composite material provided by the invention comprises the ternary core and the lithium iron manganese phosphate coating layer coated on the surface of the core, has good homogenate dispersibility, and the ternary core and the lithium iron manganese phosphate coating layer are both doped with rare earth dysprosium, so that the composite material has high conductivity and excellent multiplying power performance and cycle performance.
Description
Technical Field
The invention belongs to the technical field of batteries, and relates to a lithium iron manganese phosphate coated ternary composite material, and a preparation method and application thereof.
Background
With the vigorous development of new energy industries in recent years, especially the rapid development of electric automobiles, the requirements of power batteries on cycle stability and specific capacity are also higher and higher. In a plurality of positive electrode material systems, the safety performance of the lithium iron manganese phosphate is superior to that of ternary lithium iron phosphate, the energy density is higher than that of the lithium iron phosphate, the cost advantage is obvious, and the lithium iron manganese phosphate is more and more favored by cell factories and host factories.
However, the olivine crystal structure of lithium iron manganese phosphate (LMFP) is poor in conductivity and rate capability, meanwhile, the Jahn-Teller effect is generated on the valence change of manganese element of the material, the polarization of the battery is increased due to elution of manganese ions, the SEI layer structure is damaged due to elution and deposition of manganese ions on the surface of a negative electrode, capacity loss is caused, and cycle performance is poor. The lithium iron manganese phosphate and the carbon material can be compounded to improve the performance of the material, and CN110247044A discloses a graphene in-situ composite lithium iron manganese phosphate positive electrode material and a preparation method thereof, wherein graphene has excellent conductivity, so that the conductivity of the composite material can be improved, but the ion conductivity of the material is not improved well. CN110323434B discloses a method for preparing a lithium iron manganese phosphate-carbon composite material and a lithium iron manganese phosphate-carbon composite material, and the patent composites lithium iron manganese phosphate with a carbon material, which can also improve the conductivity of lithium iron manganese phosphate, but the ionic conductivity of lithium iron manganese phosphate is difficult to improve, so that the cycle performance of the lithium iron manganese phosphate is difficult to improve.
And mix ternary positive pole material in lithium iron manganese phosphate, can improve conductivity, multiplying power performance and cycle performance of lithium iron manganese phosphate at the same time, CN104300123B has disclosed a kind of mixed positive pole material, positive pole piece and lithium ion battery using this positive pole material, this mixed positive pole material includes the component of the following weight portion: 50-90 parts of nickel-cobalt-manganese ternary material and 10-50 parts of lithium iron manganese phosphate. The patent compounds a nickel-cobalt-manganese ternary material with high energy density and lithium iron manganese phosphate with high safety performance. However, when the lithium iron manganese phosphate and the ternary material are directly mixed, the homogenization process is difficult, and the dispersibility of the slurry is poor.
Therefore, there is a need to develop a composite material of lithium iron manganese phosphate and ternary material to solve the problems of poor homogenization dispersibility of the mixed material of lithium iron manganese phosphate and ternary material, poor conductivity, poor rate capability and poor cycle performance with pure lithium iron manganese phosphate.
Disclosure of Invention
Aiming at the defects existing in the prior art, the invention aims to provide a lithium iron manganese phosphate coated ternary composite material, and a preparation method and application thereof. The composite material provided by the invention comprises the ternary core and the lithium iron manganese phosphate coating layer coated on the surface of the core, has good homogenate dispersibility, and the ternary core and the lithium iron manganese phosphate coating layer are both doped with rare earth dysprosium, so that the composite material has high conductivity and excellent multiplying power performance and cycle performance.
To achieve the purpose, the invention adopts the following technical scheme:
in a first aspect, the invention provides a lithium iron manganese phosphate coated ternary composite material, which comprises a ternary core and a lithium iron manganese phosphate coating layer coated on the surface of the core;
dysprosium elements are doped in the ternary core and the lithium iron manganese phosphate coating layer.
The invention provides a lithium iron manganese phosphate coated ternary composite material, wherein a ternary core and a lithium iron manganese phosphate coating layer in the composite material are integrated, so that the composite material has good homogenate dispersibility; meanwhile, rare earth dysprosium is doped in the ternary core and the lithium iron manganese phosphate coating layer, so that the problems of poor conductivity and large self-discharge of pure lithium iron manganese phosphate are solved, and the structural stability of the composite material is effectively improved by doping the rare earth dysprosium, so that the composite material shows excellent multiplying power performance and cycle performance.
Preferably, the ternary core comprises dysprosium element doped nickel cobalt manganese ternary positive electrode material and/or dysprosium element doped nickel cobalt aluminum ternary positive electrode material.
Preferably, the mass ratio of the ternary core to the lithium iron manganese phosphate coating layer is (0.1-0.3): (0.7-0.9), wherein the selection range (0.1-0.3) of the ternary core can be, for example, 0.1, 0.15, 0.2, 0.25 or 0.3, and the selection range (0.7-0.9) of the lithium iron manganese phosphate coating layer can be, for example, 0.7, 0.75, 0.8, 0.85 or 0.9, and the like.
Preferably, the thickness of the lithium manganese iron phosphate coating layer is 0.1-0.5 μm, and may be, for example, 0.1 μm, 0.15 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, or 0.5 μm, etc.
Preferably, the mass content of dysprosium in the lithium manganese iron phosphate coating layer is 1-3%, for example, 1%, 1.5%, 2%, 2.5% or 3%.
Preferably, the mass content of dysprosium in the ternary core is 1-3%, for example, 1%, 1.5%, 2%, 2.5% or 3%, etc.
In the invention, if the content of dysprosium element in the lithium manganese iron phosphate coating layer and the ternary core is too low, dysprosium element cannot play a role in stabilizing the crystal structure of the positive electrode material, so that the first-week coulomb efficiency of the composite material is difficult to improve; if the content of dysprosium element in the lithium iron manganese phosphate coating layer and the ternary core is too high, excessive dysprosium can prevent lithium ions from deintercalating, and the impedance of the material is increased.
In a second aspect, the invention provides a preparation method of the lithium iron manganese phosphate coated ternary composite material in the first aspect, which comprises the following steps:
(1) Respectively preparing a lithium iron manganese phosphate precursor and a ternary precursor:
wherein, the method for preparing the ternary precursor comprises the following steps: mixing a nickel source, a cobalt source, a manganese source, a solvent and an alkaline solution, performing coprecipitation reaction to obtain a precipitate, and calcining the precipitate to obtain a ternary precursor;
(2) And mixing the lithium iron manganese phosphate precursor, the ternary precursor, a lithium source and a dysprosium source, and sintering to obtain the lithium iron manganese phosphate coated ternary composite material.
The preparation of the lithium iron manganese phosphate precursor and the preparation of the ternary precursor are not sequential in time, and the lithium iron manganese phosphate precursor, the ternary precursor and the lithium iron manganese phosphate precursor can be prepared first, and the lithium iron manganese phosphate precursor and the ternary precursor can be prepared simultaneously.
In the invention, the precipitate in the step (1) cannot be formed without calcining, and contains a large amount of water molecules and some impurities, so that the performance of the positive electrode material is directly affected.
Preferably, the method for preparing the lithium iron manganese phosphate precursor comprises the following steps: and mixing a manganese source, an iron source and a phosphorus source, and sintering to obtain the lithium iron manganese phosphate precursor.
Optionally, in the method of preparing the lithium iron manganese phosphate precursor, the manganese source includes MnSO 4 、Mn(NO 3 ) 2 And MnCl 2 At least one of them.
Optionally, in the method for preparing the lithium iron manganese phosphate precursor, the iron source includes FeSO 4 、Fe(NO 3 ) 2 And FeCl 2 At least one of them.
Optionally, in the method for preparing the lithium manganese iron phosphate precursor, the phosphorus source includes H 3 PO 4 。
Preferably, in the method for preparing the lithium iron manganese phosphate precursor, the molar ratio of the manganese source, the iron source and the phosphorus source is (0.5-0.7): (0.3-0.5): 1, wherein the manganese source may be selected from the range of (0.5-0.7) such as 0.5, 0.55, 0.6, 0.65 or 0.7, and the iron source may be selected from the range of (0.3-0.5) such as 0.3, 0.35, 0.4, 0.45 or 0.5.
Preferably, in the method of preparing the lithium manganese iron phosphate precursor, the sintering temperature is 250-350 ℃, for example, 250 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃, or the like.
Preferably, in the method for preparing the lithium iron manganese phosphate precursor, the sintering time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h, 3h, or the like.
Preferably, in the method for preparing the lithium manganese iron phosphate precursor, the sintering atmosphere is a reducing atmosphere, and gases in the reducing atmosphere include, but are not limited to, argon and hydrogen.
Optionally, in the method of preparing the ternary precursor, the nickel source includes Ni (NO 3 ) 2 ·6H 2 O and/or Ni (SO) 4 )。
Optionally, in the method of preparing the ternary precursor, the cobalt source comprises Co (NO 3 ) 2 ·6H 2 O and/or CoSO 4 。
Alternatively, in the method of preparing the ternary precursor, the manganese source includes Mn (CH 3 COO) 2 ·4H 2 O and/or MnSO 4 。
Preferably, in the method for preparing the ternary precursor, the molar ratio of the nickel source, the cobalt source and the manganese source is (5-7): 1 (2-4), wherein the nickel source may be selected from the range (5-7) of, for example, 5, 5.5, 6, 6.5 or 7, etc., and the manganese source may be selected from the range (2-4) of, for example, 2, 2.5, 3, 3.5 or 4, etc.
Preferably, in the method of preparing the ternary precursor, the mixed raw materials further include at least one of sodium nitrite solution, sodium persulfate (APS) solution, and polyvinylpyrrolidone (PVP).
Preferably, the concentration of the sodium nitrite solution is 0.4-0.5g/L, and can be, for example, 0.4g/L, 0.41g/L, 0.42g/L, 0.43g/L, 0.44g/L, 0.45g/L, 0.46g/L, 0.47g/L, 0.48g/L, 0.49g/L, 0.5g/L, or the like.
Preferably, the ratio of the molar amount of sodium nitrite in the sodium nitrite solution to the total molar amount of the nickel source, cobalt source and manganese source is (2-5): (95-98), wherein the sodium nitrite selection range (2-5) may be, for example, 2, 2.5, 3, 3.5, 4, 4.5 or 5, etc.; the total molar amount of the nickel source, cobalt source and manganese source may be selected from the range (95-98), for example, 95, 95.5, 96, 96.5, 97, 97.5 or 98.
Preferably, the solvent of step (1) comprises water.
Preferably, the alkaline solution of step (1) comprises aqueous ammonia and/or sodium hydroxide solution.
Preferably, in the method of preparing the ternary precursor, the mixing is stepwise mixing comprising: firstly, mixing the nickel source, the cobalt source, the manganese source and the solvent for the first time, and then mixing the mixture with the sodium nitrite solution and the alkaline solution for the second time.
Preferably, the temperature of the coprecipitation reaction in step (1) is 60 to 70℃and may be, for example, 60℃61℃62℃63℃64℃65℃66℃67℃68℃69℃70 ℃.
Preferably, the pH of the coprecipitation reaction in step (1) is 9-11, and may be, for example, 9, 9.5, 10, 10.5 or 11.
Preferably, stirring is carried out during the coprecipitation reaction in the step (1), and the stirring rotation speed is 200-400r/min, for example, 200r/min, 220r/min, 240r/min, 260r/min, 300r/min, 320r/min, 340r/min, 360r/min, 380r/min or 400r/min and the like.
Preferably, the time of the coprecipitation reaction in step (1) is 1 to 3 hours, for example, 1 hour, 1.5 hours, 2 hours, 2.5 hours, 3 hours, etc.
Preferably, the temperature of the calcination in the step (1) is 450-550 ℃, and for example, 450 ℃, 460 ℃, 470 ℃, 480 ℃, 490 ℃, 500 ℃, 510 ℃, 520 ℃, 530 ℃, 540 ℃, 550 ℃ or the like can be used.
Preferably, the calcination in step (1) takes 4 to 6 hours, for example, 4 hours, 4.5 hours, 5 hours, 5.5 hours, or 6 hours.
Preferably, the atmosphere of the calcination of step (1) is an oxygen-containing atmosphere, and the gases in the oxygen-containing atmosphere include, but are not limited to, oxygen.
Preferably, the mass ratio of the lithium manganese iron phosphate precursor, the ternary precursor and the lithium source in the step (2) is (0.6-0.8): (0.2-0.4): 1, wherein the selection range (0.6-0.8) of the lithium manganese iron phosphate precursor can be, for example, 0.6, 0.62, 0.64, 0.66, 0.68, 0.7, 0.72, 0.74, 0.76, 0.78 or 0.8, and the like, and the selection range (0.2-0.4) of the ternary precursor can be, for example, 0.2, 0.22, 0.24, 0.26, 0.28, 0.3, 0.32, 0.34, 0.36, 038 or 0.4, and the like.
Preferably, the dysprosium source of step (2) comprises a dysprosium nitrate solution and/or a dysprosium sulfate solution.
In one embodiment, the dysprosium source of step (2) is added in an amount sufficient to completely infiltrate the lithium iron manganese phosphate precursor, the ternary precursor, and the lithium source.
Preferably, the dysprosium nitrate solution has a concentration of 0.1 to 0.4mol/L, and may be, for example, 0.1mol/L, 0.12mol/L, 0.15mol/L, 0.17mol/L, 0.2mol/L, 0.22mol/L, 0.25mol/L, 0.27mol/L, 0.3mol/L, 0.32mol/L, 0.35mol/L, 0.37mol/L, or 0.4mol/L, etc.
Preferably, step (2) further comprises: and a step of grinding and drying is sequentially performed between the step of mixing and the step of sintering.
Preferably, the grinding time is 5-7h, for example, 5h, 5.5h, 6h, 6.5h or 7h, etc.
Preferably, the mixing of step (2) is a stepwise mixing comprising: firstly, carrying out primary mixing on the lithium iron manganese phosphate precursor, the ternary precursor and a lithium source, and then carrying out secondary mixing on the lithium iron manganese phosphate precursor, the ternary precursor and the lithium source and the dysprosium source.
Preferably, the secondary mixing mode comprises stirring, and the stirring rotation speed is 200-400r/min, for example, 200r/min, 220r/min, 240r/min, 260r/min, 300r/min, 320r/min, 340r/min, 360r/min, 380r/min or 400r/min and the like.
Preferably, the secondary mixing time is 1-3h, for example, 1h, 1.5h, 2h, 2.5h, 3h, etc.
Preferably, the temperature of the secondary mixing is 40-50deg.C, which may be, for example, 40deg.C, 41 deg.C, 42 deg.C, 43 deg.C, 44 deg.C, 45 deg.C, 46 deg.C, 47 deg.C, 48 deg.C, 49 deg.C, 50 deg.C, etc.
Preferably, the sintering of step (2) is a step-by-step sintering comprising: the primary sintering is carried out firstly, and then the secondary sintering is carried out.
In the present invention, if the primary sintering is not performed but only the secondary sintering is performed, the morphology and particle size of the material are affected.
Preferably, the temperature of the primary sintering is 250-350 ℃, for example, 250 ℃, 260 ℃, 270 ℃, 280 ℃, 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃ or the like can be used.
Preferably, the time of the primary sintering is 5-7h, for example, 5h, 5.5h, 6h, 6.5h or 7h, etc.
Preferably, the temperature of the secondary sintering is 600-700 ℃, and for example, 600 ℃, 610 ℃, 620 ℃, 630 ℃, 640 ℃, 650 ℃, 660 ℃, 670 ℃, 680 ℃, 690 ℃, 700 ℃ or the like can be used.
Preferably, the time of the secondary sintering is 9-11h, for example, 9h, 9.5h, 10h, 10.5h or 11h, etc.
Preferably, the primary sintering atmosphere and the secondary sintering atmosphere are both inert atmospheres, and the gases in the inert atmospheres include, but are not limited to, nitrogen.
In a third aspect, the invention provides a lithium ion battery, wherein the positive electrode of the lithium ion battery comprises the lithium manganese iron phosphate coated ternary composite material of the first aspect.
The numerical ranges recited herein include not only the above-listed point values, but also any point values between the above-listed numerical ranges that are not listed, and are limited in space and for the sake of brevity, the present invention is not intended to be exhaustive of the specific point values that the stated ranges include.
Compared with the prior art, the invention has the beneficial effects that:
the invention provides a lithium iron manganese phosphate coated ternary composite material, wherein a ternary core and a lithium iron manganese phosphate coating layer in the composite material are integrated, so that the composite material has good homogenate dispersibility; meanwhile, rare earth dysprosium is doped in the ternary core and the lithium iron manganese phosphate coating layer, so that the problems of poor conductivity and large self-discharge of pure lithium iron manganese phosphate are solved, and the structural stability of the composite material is effectively improved by doping the rare earth dysprosium, so that the composite material shows excellent multiplying power performance and cycle performance.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments.
Example 1
The embodiment provides a lithium manganese iron phosphate coated ternary composite material, which comprises a ternary core and a lithium manganese iron phosphate coating layer coated on the surface of the core, dysprosium elements are doped in the ternary core and the lithium manganese iron phosphate coating layer, the ternary core is a dysprosium element doped nickel cobalt manganese ternary positive electrode material, the mass ratio of the ternary core to the lithium manganese iron phosphate coating layer is 3:7, the thickness of the lithium manganese iron phosphate coating layer is 0.4 mu m, the mass content of dysprosium in the lithium manganese iron phosphate coating layer is 2%, and the mass content of dysprosium in the ternary core is 2%.
The embodiment also provides a preparation method of the lithium iron manganese phosphate coated ternary composite material, which comprises the following steps:
(1) In MnSO 4 、FeSO 4 And H 3 PO 4 Weighing all materials according to the molar ratio of Mn, fe and P elements of 0.6:0.4:1, uniformly mixing, and presintering for 2 hours in an argon-hydrogen (wherein the content of hydrogen is 20%) mixed atmosphere at 300 ℃ to obtain lithium iron manganese phosphate precursor powder;
(2) With Ni (NO) 3 ) 2 ·6H 2 O、Co(NO 3 ) 2 ·6H 2 O and Mn (CH) 3 COO) 2 ·4H 2 O is used as a raw material, ni, co and Mn are dissolved in deionized water according to the molar ratio of 6:1:3 to prepare a nickel-cobalt-manganese mixed salt solution, 0.45g/L sodium nitrite solution is added into the mixed salt solution, the molar ratio of sodium nitrite to the total molar ratio of a nickel source, a cobalt source and a manganese source is 3:97, 5L of 10% ammonia water and 1.5mol/L sodium hydroxide solution are added, the temperature of the solution is controlled at 65 ℃, the pH value is controlled at 10 by using a nitric acid solution, the solution is stirred for 2 hours at 300r/min, and the precipitate is calcined in an oxygen atmosphere at 500 ℃ for 5 hours after filtration and drying, so as to obtain ternary precursor powder;
(3) Mixing the lithium iron manganese phosphate precursor, the ternary precursor and lithium carbonate according to the mass ratio of 0.7:0.3:1 to obtain a mixture, adding the mixture into a dysprosium nitrate solution with the mass ratio of 0.3mol/L, fully soaking the mixture, stirring at 45 ℃ for 2 hours at 300r/min, putting the dispersed slurry into a sand mill, grinding for 6 hours, drying the ground slurry into powder by using a pressure spray dryer, sintering at 300 ℃ for 6 hours at the nitrogen atmosphere, and sintering at 650 ℃ for 10 hours for the second time to obtain the lithium iron manganese phosphate coated ternary composite material.
Example 2
This example differs from example 1 in that the concentration of dysprosium nitrate solution in step (3) was adjusted to 0.1mol/L, and the remainder was exactly the same as example 1.
Example 3
This example differs from example 1 in that the concentration of dysprosium nitrate solution in step (3) was adjusted to 0.2mol/L, and the remainder was exactly the same as example 1.
Example 4
This example differs from example 1 in that the concentration of dysprosium nitrate solution in step (3) was adjusted to 0.4mol/L, and the remainder was exactly the same as example 1.
Example 5
The embodiment provides a lithium manganese iron phosphate coated ternary composite material, which comprises a ternary core and a lithium manganese iron phosphate coating layer coated on the surface of the core, dysprosium elements are doped in the ternary core and the lithium manganese iron phosphate coating layer, the ternary core is a dysprosium element doped nickel cobalt manganese ternary positive electrode material, the mass ratio of the ternary core to the lithium manganese iron phosphate coating layer is 2:8, the thickness of the lithium manganese iron phosphate coating layer is 0.2 mu m, the mass content of dysprosium in the lithium manganese iron phosphate coating layer is 1%, and the mass content of dysprosium in the ternary core is 1%.
The embodiment also provides a preparation method of the lithium iron manganese phosphate coated ternary composite material, which comprises the following steps:
(1) In MnSO 4 、FeSO 4 And H 3 PO 4 Weighing all materials according to the molar ratio of Mn, fe and P elements of 0.5:0.5:1, uniformly mixing, and presintering for 3 hours in an argon-hydrogen (wherein the content of hydrogen is 20%) mixed atmosphere at 250 ℃ to obtain lithium iron manganese phosphate precursor powder;
(2) With Ni (NO) 3 ) 2 ·6H 2 O、Co(NO 3 ) 2 ·6H 2 O and Mn (CH) 3 COO) 2 ·4H 2 O is used as a raw material, ni, co and Mn are dissolved in deionized water according to the molar ratio of 5:1:4 to prepare a nickel-cobalt-manganese mixed salt solution, 0.4g/L sodium nitrite solution is added into the mixed salt solution, the ratio of the molar quantity of sodium nitrite to the total molar quantity of the nickel source, the cobalt source and the manganese source is 3:97, and 5L of 10% ammonia is added simultaneouslyWater and 1L of 1.5mol/L sodium hydroxide solution, controlling the temperature of the solution at 60 ℃, controlling the pH value at 9 by using nitric acid solution, stirring for 3h at 200r/min, filtering, drying, and calcining the precipitate in an oxygen atmosphere at 450 ℃ for 6h to obtain ternary precursor powder;
(3) Mixing the lithium iron manganese phosphate precursor, the ternary precursor and lithium carbonate according to the mass ratio of 0.6:0.2:1 to obtain a mixture, adding the mixture into a dysprosium nitrate solution with the mass ratio of 0.2mol/L, fully soaking the mixture, stirring at the temperature of 40 ℃ for 3 hours at the speed of 200r/min, putting the dispersed slurry into a sand mill, grinding for 5 hours, drying the ground slurry into powder by using a pressure spray dryer, sintering at the temperature of 250 ℃ for 7 hours at one time in a nitrogen atmosphere, and sintering at the temperature of 600 ℃ for 11 hours for the second time to obtain the lithium iron manganese phosphate coated ternary composite material.
Example 6
The embodiment provides a lithium manganese iron phosphate coated ternary composite material, which comprises a ternary core and a lithium manganese iron phosphate coating layer coated on the surface of the core, dysprosium elements are doped in the ternary core and the lithium manganese iron phosphate coating layer, the ternary core is a dysprosium element doped nickel cobalt manganese ternary positive electrode material, the mass ratio of the ternary core to the lithium manganese iron phosphate coating layer is 1:9, the thickness of the lithium manganese iron phosphate coating layer is 0.3 mu m, the mass content of dysprosium in the lithium manganese iron phosphate coating layer is 3%, and the mass content of dysprosium in the ternary core is 3%.
The embodiment also provides a preparation method of the lithium iron manganese phosphate coated ternary composite material, which comprises the following steps:
(1) In MnSO 4 、FeSO 4 And H 3 PO 4 Weighing all materials according to the molar ratio of Mn, fe and P elements of 0.7:0.3:1, uniformly mixing, and presintering for 1h in an argon-hydrogen (wherein the content of hydrogen is 20%) mixed atmosphere at 350 ℃ to obtain lithium iron manganese phosphate precursor powder;
(2) With Ni (NO) 3 ) 2 ·6H 2 O、Co(NO 3 ) 2 ·6H 2 O and Mn (CH) 3 COO) 2 ·4H 2 O is used as a raw material, ni, co and Mn are dissolved in deionized water according to the molar ratio of 7:1:2 to prepare a nickel-cobalt-manganese mixed salt solution, 0.5g/L sodium nitrite solution is added into the mixed salt solution, the molar ratio of sodium nitrite to the total molar ratio of a nickel source, a cobalt source and a manganese source is 3:97, 5L of 10% ammonia water and 1.5mol/L sodium hydroxide solution are added, the temperature of the solution is controlled at 70 ℃, the pH value is controlled at 11 by using nitric acid solution, the solution is stirred for 1h at 400r/min, and the precipitate is calcined for 4h in an oxygen atmosphere at 550 ℃ after filtration and drying, so as to obtain ternary precursor powder;
(3) Mixing the lithium iron manganese phosphate precursor, the ternary precursor and lithium carbonate according to the mass ratio of 0.8:0.4:1 to obtain a mixture, adding the mixture into a dysprosium nitrate solution with the mass ratio of 0.4mol/L, fully soaking the mixture, stirring at the temperature of 50 ℃ for 1h at the speed of 400r/min, putting the dispersed slurry into a sand mill, grinding for 7h, drying the ground slurry into powder by using a pressure spray dryer, sintering at the temperature of 350 ℃ for 5h at one time under nitrogen atmosphere, and sintering at the temperature of 700 ℃ for 9h for the second time to obtain the lithium iron manganese phosphate coated ternary composite material.
Example 7
The difference between this example and example 1 is that the dysprosium nitrate solution concentration in step (3) was adjusted to 0.05mol/L so that the dysprosium element content in both the ternary core and the lithium iron manganese phosphate coating layer was adjusted to 0.03%, and the remainder was identical to example 1.
Example 8
The difference between this example and example 1 is that the dysprosium nitrate solution concentration in step (3) was adjusted to 0.5mol/L so that the dysprosium element content in the ternary core and the lithium iron manganese phosphate coating layer were both adjusted to 4%, and the remainder was identical to example 1.
Example 9
The difference between this example and example 1 is that the step sintering in step (3) was adjusted to be performed for only secondary sintering, not primary sintering, that is, sintering at 650 ℃ for only 10 hours, and the rest was exactly the same as example 1.
Example 10
This example differs from example 1 in that in step (2), the sodium nitrite solution is not added to the mixed salt solution, and the rest is exactly the same as example 1.
Comparative example 1
The difference between this comparative example and example 1 is that the dysprosium nitrate solution in step (3) was replaced with water so that the ternary core and the lithium iron manganese phosphate cladding were doped with no dysprosium element, and the remainder was exactly the same as example 1.
Comparative example 2
The difference between the comparative example and the example 1 is that in the step (3), the ternary precursor is added into dysprosium nitrate solution, stirred and dried to obtain the ternary precursor doped with dysprosium element; and then mixing the ternary precursor doped with dysprosium element, the lithium iron manganese phosphate precursor and lithium carbonate, and sequentially stirring, grinding and sintering step by step, so that only the ternary core in the composite material is doped with dysprosium element, the lithium iron manganese phosphate coating layer is doped with no dysprosium element, and the rest is completely the same as the embodiment 1.
Comparative example 3
The comparison example provides a preparation method of a lithium manganese iron phosphate coated ternary composite material, which is different from the embodiment 1 in that in the step (3), a lithium manganese iron phosphate precursor is firstly added into dysprosium nitrate solution, and is dried after stirring, so as to obtain the dysprosium element doped lithium manganese iron phosphate precursor; and then mixing the dysprosium doped lithium iron manganese phosphate precursor, the ternary precursor and lithium carbonate, and sequentially stirring, grinding and sintering step by step, so that only the dysprosium doped in the lithium iron manganese phosphate coating layer in the composite material is doped, the dysprosium doped in the ternary core is not doped, and the rest is completely the same as the embodiment 1.
Comparative example 4
This comparative example differs from example 1 in that the precipitate in step (2) was not calcined, and the remainder was exactly the same as example 1.
Performance testing
The composite cathode materials provided in examples 1 to 10 and comparative examples 1 to 4, acetylene black and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 92% to 4% to prepare a slurry, the slurry was uniformly coated on an aluminum foil, and vacuum-dried at 110 °cDrying for 10h, compacting the pole piece under the pressure of 20Mpa, and cutting the pole piece into pole pieces with the diameter of 14mm to obtain a positive pole piece; then, the positive plate is assembled into a CR2032 button cell in a glove box, wherein the negative electrode is metallic lithium, the diaphragm is a celgard 2400 polyolefin microporous membrane, and the electrolyte is 1M LiPF 6 Dissolved in a mixed solvent of dimethyl carbonate (DMC), ethylene Carbonate (EC) and diethyl carbonate (DEC) in a volume ratio of 1:1:1. The electrochemical test of the battery is carried out by a blue electricity tester, which comprises the following steps:
(1) Initial specific capacity test: and (3) carrying out charge and discharge test on the battery at 25+/-2 ℃, wherein the charge and discharge test voltage is 2.5-4.2V, the charge and discharge current multiplying power is 1.0C, and the capacity of the positive electrode material of 1C is tested.
(2) 60 days self-discharge test: under the environment of 25+/-2 ℃, the battery is charged to 4.2V at constant current and constant voltage of 1C, and is cut off at 0.02C, and the battery is placed in the environment of 25 ℃ for continuous storage for 60 days, and the voltage drop of the battery cell is measured after 60 days of storage.
(3) And (3) multiplying power performance test: and (3) performing charge and discharge tests at 25+/-2 ℃ under the conditions that the charge and discharge voltage is 2.5-4.2V, the discharge current density is 1C and 5C respectively, and calculating the discharge capacity at 5C rate divided by the discharge capacity at 1C rate to obtain larger values, wherein the larger values represent better rate performance of the positive electrode material.
(4) And (3) testing the cycle performance: under the environment of 25+/-2 ℃, the battery is charged to a cut-off voltage of 4.2V at a constant current of 1C, then is charged to a current of 0.05C at a constant voltage, and is kept stand for 30min; the discharge was discharged at a constant current of 1C to a cut-off voltage of 2.5V. The charge and discharge cycle was 100 weeks, and the first cycle discharge capacity was recorded as E 1 The second cycle discharge capacity was recorded as E 2 ，E 2 /E 1 Namely, the 100-circle capacity cycle retention rate is obtained, and the larger the retention rate value is, the better the cycle performance of the positive electrode material is.
The test results are shown in Table 1.
TABLE 1
Analysis:
from the results of examples 1-6, it can be seen that the lithium iron manganese phosphate coated ternary composite material provided by the invention has higher conductivity, the corresponding battery shows higher coulombic efficiency, higher capacity, excellent rate capability and excellent cycle performance, and the 60-day self-discharge of the battery is less.
From a comparison of the results of example 1 and examples 7-8, it is clear that the concentration of dysprosium nitrate solution affects the dysprosium element content in the ternary core and the lithium iron manganese phosphate coating. When the contents of dysprosium elements in the ternary core and the lithium iron manganese phosphate coating layer are too low, the dysprosium elements cannot play a role in stabilizing the crystal structure of the positive electrode material, and the first effect of the composite material is difficult to improve; when the contents of dysprosium elements in the ternary core and the lithium iron manganese phosphate coating layer are too high, excessive dysprosium can prevent lithium ions from deintercalating, and the impedance of the material is increased, so that the first effect, gram capacity and capacity retention rate of the composite material are affected.
As is clear from comparison of the results of example 1 and example 9, if only secondary sintering is performed in step (3) instead of primary sintering, the morphology formation of the material is affected, and the particle size of the material is larger, which directly results in lower initial efficiency and poorer rate performance of the material.
As can be seen from the data of examples 1 and 10, if the sodium nitrite solution is not added to the mixed salt solution in the step (2), the generated ternary precursor is affected, so that the electrochemical performance of the lithium iron manganese phosphate coated ternary composite material is affected, the initial efficiency and gram capacity are low, the rate performance and the cycle performance are poor, and the 60-day self-discharge of the battery is more.
From the results of example 1 and comparative examples 1 to 3, it is understood that when rare earth dysprosium is not doped in the ternary core and/or the lithium iron manganese phosphate coating layer, the battery corresponding to the composite material exhibits lower coulombic efficiency, lower capacity, poorer rate capability and poorer cycle performance, and the 60-day self-discharge of the battery is more. This indicates that the doping of rare earth dysprosium in the ternary core and the lithium iron manganese phosphate coating is critical.
As is clear from comparison of the results of example 1 and comparative example 4, if the precipitate is not calcined in step (2), the moisture content of the ternary precursor is high, and the precursor is free from fixed morphology, which is unfavorable for the lithium ion bulk density of the material, and affects the gram capacity and electrical performance of the positive electrode material.
The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.
Claims (10)
1. The lithium iron manganese phosphate coated ternary composite material is characterized by comprising a ternary core and a lithium iron manganese phosphate coating layer coated on the surface of the core;
dysprosium elements are doped in the ternary core and the lithium iron manganese phosphate coating layer.
2. The composite material of claim 1, wherein the ternary core comprises a dysprosium element doped nickel cobalt manganese ternary cathode material and/or a dysprosium element doped nickel cobalt aluminum ternary cathode material;
preferably, the mass ratio of the ternary core to the lithium iron manganese phosphate coating layer is (0.1-0.3): 0.7-0.9;
preferably, the thickness of the lithium iron manganese phosphate coating layer is 0.1-0.5 mu m.
3. The composite material according to claim 1 or 2, wherein the mass content of dysprosium in the lithium iron manganese phosphate coating is 1-3%;
preferably, the mass content of dysprosium in the ternary core is 1-3%.
4. A method for preparing the lithium iron manganese phosphate coated ternary composite material according to any one of claims 1 to 3, wherein the preparation method comprises the following steps:
(1) Respectively preparing a lithium iron manganese phosphate precursor and a ternary precursor:
wherein, the method for preparing the ternary precursor comprises the following steps: mixing a nickel source, a cobalt source, a manganese source, a solvent and an alkaline solution, performing coprecipitation reaction to obtain a precipitate, and calcining the precipitate to obtain a ternary precursor;
(2) And mixing the lithium iron manganese phosphate precursor, the ternary precursor, a lithium source and a dysprosium source, and sintering to obtain the lithium iron manganese phosphate coated ternary composite material.
5. The method of preparing the lithium iron manganese phosphate precursor according to claim 4, comprising: mixing a manganese source, an iron source and a phosphorus source, and sintering to obtain a lithium iron manganese phosphate precursor;
preferably, in the method for preparing the lithium iron manganese phosphate precursor, the molar ratio of the manganese source to the iron source to the phosphorus source is (0.5-0.7): 0.3-0.5): 1;
preferably, in the method for preparing the lithium iron manganese phosphate precursor, the sintering temperature is 250-350 ℃;
preferably, in the method for preparing the lithium iron manganese phosphate precursor, the sintering time is 1-3h;
preferably, in the method for preparing the lithium iron manganese phosphate precursor, the sintering atmosphere is a reducing atmosphere.
6. The method according to claim 4 or 5, wherein in the method for producing the ternary precursor, the molar ratio of the nickel source, cobalt source and manganese source is (5-7): 1 (2-4);
preferably, in the method for preparing the ternary precursor, the mixed raw materials further include at least one of sodium nitrite solution, sodium persulfate solution and polyvinylpyrrolidone;
preferably, the concentration of the sodium nitrite solution is 0.4-0.5g/L;
preferably, the ratio of the molar amount of sodium nitrite in the sodium nitrite solution to the total molar amount of the nickel source, cobalt source and manganese source is (2-5): (95-98);
preferably, the solvent of step (1) comprises water;
preferably, the alkaline solution of step (1) comprises aqueous ammonia and/or sodium hydroxide solution.
7. The method of any one of claims 4-6, wherein in the method of preparing the ternary precursor, the mixing is stepwise mixing comprising: firstly, mixing the nickel source, the cobalt source, the manganese source and the solvent for the first time, and then mixing the mixture with the sodium nitrite solution and the alkaline solution for the second time;
preferably, the temperature of the coprecipitation reaction in step (1) is 60-70 ℃;
preferably, the pH of the coprecipitation reaction of step (1) is 9-11;
preferably, stirring is carried out in the coprecipitation reaction process in the step (1), and the rotating speed of stirring is 200-400r/min;
preferably, the time of the coprecipitation reaction in step (1) is 1 to 3 hours;
preferably, the temperature of the calcination in step (1) is 450-550 ℃;
preferably, the calcination in step (1) takes 4 to 6 hours;
preferably, the atmosphere of the calcination in step (1) is an oxygen-containing atmosphere.
8. The method according to any one of claims 4 to 7, wherein the mass ratio of the lithium iron manganese phosphate precursor, the ternary precursor and the lithium source in step (2) is (0.6 to 0.8): (0.2 to 0.4): 1;
preferably, the dysprosium source of step (2) comprises a dysprosium nitrate solution and/or a dysprosium sulfate solution;
preferably, the concentration of the dysprosium nitrate solution is 0.1-0.4mol/L;
preferably, step (2) further comprises: a step of grinding and drying sequentially between the step of mixing and the step of sintering;
preferably, the milling is for a period of time ranging from 5 to 7 hours.
9. The method of any one of claims 4-8, wherein the mixing in step (2) is a stepwise mixing comprising: firstly, carrying out primary mixing on the lithium iron manganese phosphate precursor, the ternary precursor and a lithium source, and then carrying out secondary mixing on the lithium iron manganese phosphate precursor, the ternary precursor and the lithium source;
preferably, the secondary mixing mode comprises stirring, wherein the stirring rotating speed is 200-400r/min;
preferably, the secondary mixing time is 1-3 hours;
preferably, the temperature of the secondary mixing is 40-50 ℃.
Preferably, the sintering of step (2) is a step-by-step sintering comprising: firstly, performing primary sintering and then performing secondary sintering;
preferably, the temperature of the primary sintering is 250-350 ℃;
preferably, the time of the primary sintering is 5-7h;
preferably, the temperature of the secondary sintering is 600-700 ℃;
preferably, the secondary sintering time is 9-11h;
preferably, the primary sintering atmosphere and the secondary sintering atmosphere are both inert atmospheres.
10. A lithium ion battery, characterized in that the positive electrode of the lithium ion battery comprises the lithium manganese iron phosphate coated ternary composite material of any one of claims 1-3.
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