CN118206094A - Preparation method of nitrogen-doped carbon-coated lithium iron phosphate positive electrode material - Google Patents
Preparation method of nitrogen-doped carbon-coated lithium iron phosphate positive electrode material Download PDFInfo
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- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 76
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 72
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 61
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 26
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims abstract description 36
- 238000001354 calcination Methods 0.000 claims abstract description 29
- 239000012298 atmosphere Substances 0.000 claims abstract description 23
- 238000001035 drying Methods 0.000 claims abstract description 22
- -1 1, 3-dimethylhydroxyethyl-5, 5-dimethylhydantoin Chemical compound 0.000 claims abstract description 20
- 239000000203 mixture Substances 0.000 claims abstract description 20
- 238000002156 mixing Methods 0.000 claims abstract description 19
- 229910052757 nitrogen Inorganic materials 0.000 claims abstract description 18
- 239000002243 precursor Substances 0.000 claims abstract description 15
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 14
- 239000010405 anode material Substances 0.000 claims abstract description 14
- 239000002904 solvent Substances 0.000 claims abstract description 9
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 8
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 8
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 5
- 239000003638 chemical reducing agent Substances 0.000 claims abstract description 5
- 229910052742 iron Inorganic materials 0.000 claims abstract description 5
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 5
- 239000011574 phosphorus Substances 0.000 claims abstract description 5
- JHKCKHHAIORJMR-UHFFFAOYSA-N 3-hydroxy-1-(1-hydroxyethyl)-5,5-dimethylimidazolidine-2,4-dione Chemical compound CC(O)N1C(=O)N(O)C(=O)C1(C)C JHKCKHHAIORJMR-UHFFFAOYSA-N 0.000 claims abstract description 4
- YVFVGFGCDDKVLP-UHFFFAOYSA-N OCCN1C=NCC1.C(CCCCCCCC=C/CCCCCCCC)(=O)O Chemical compound OCCN1C=NCC1.C(CCCCCCCC=C/CCCCCCCC)(=O)O YVFVGFGCDDKVLP-UHFFFAOYSA-N 0.000 claims abstract description 3
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 19
- 238000000498 ball milling Methods 0.000 claims description 18
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 12
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 9
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 9
- 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 8
- 239000008103 glucose Substances 0.000 claims description 8
- 238000000034 method Methods 0.000 claims description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 6
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 6
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 5
- 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 5
- BPXVHIRIPLPOPT-UHFFFAOYSA-N 1,3,5-tris(2-hydroxyethyl)-1,3,5-triazinane-2,4,6-trione Chemical compound OCCN1C(=O)N(CCO)C(=O)N(CCO)C1=O BPXVHIRIPLPOPT-UHFFFAOYSA-N 0.000 claims description 4
- KXGFMDJXCMQABM-UHFFFAOYSA-N 2-methoxy-6-methylphenol Chemical compound [CH]OC1=CC=CC([CH])=C1O KXGFMDJXCMQABM-UHFFFAOYSA-N 0.000 claims description 4
- 239000005955 Ferric phosphate Substances 0.000 claims description 4
- 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 4
- 229930006000 Sucrose Natural products 0.000 claims description 4
- 239000006229 carbon black Substances 0.000 claims description 4
- 229940032958 ferric phosphate Drugs 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 4
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 4
- 239000012299 nitrogen atmosphere Substances 0.000 claims description 4
- 239000005011 phenolic resin Substances 0.000 claims description 4
- 229920001568 phenolic resin Polymers 0.000 claims description 4
- 239000005720 sucrose Substances 0.000 claims description 4
- 239000004254 Ammonium phosphate Substances 0.000 claims description 2
- MCDLETWIOVSGJT-UHFFFAOYSA-N acetic acid;iron Chemical compound [Fe].CC(O)=O.CC(O)=O MCDLETWIOVSGJT-UHFFFAOYSA-N 0.000 claims description 2
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019289 ammonium phosphates Nutrition 0.000 claims description 2
- 239000008367 deionised water Substances 0.000 claims description 2
- 229910021641 deionized water Inorganic materials 0.000 claims description 2
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 2
- 229940062993 ferrous oxalate Drugs 0.000 claims description 2
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 2
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 2
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 2
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 2
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 claims description 2
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 2
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 claims 1
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims 1
- 239000000463 material Substances 0.000 abstract description 7
- 238000004519 manufacturing process Methods 0.000 abstract description 6
- 230000005540 biological transmission Effects 0.000 abstract description 3
- 150000002500 ions Chemical class 0.000 abstract description 3
- 238000005303 weighing Methods 0.000 description 15
- 239000007789 gas Substances 0.000 description 14
- 239000002994 raw material Substances 0.000 description 9
- 238000010438 heat treatment Methods 0.000 description 7
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 229910001416 lithium ion Inorganic materials 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 4
- POULHZVOKOAJMA-UHFFFAOYSA-N dodecanoic acid Chemical compound CCCCCCCCCCCC(O)=O POULHZVOKOAJMA-UHFFFAOYSA-N 0.000 description 4
- 125000001477 organic nitrogen group Chemical group 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 3
- 239000002131 composite material Substances 0.000 description 3
- 239000002086 nanomaterial Substances 0.000 description 3
- 238000003746 solid phase reaction Methods 0.000 description 3
- 239000000126 substance Substances 0.000 description 3
- 238000012360 testing method Methods 0.000 description 3
- GOHZKUSWWGUUNR-UHFFFAOYSA-N 2-(4,5-dihydroimidazol-1-yl)ethanol Chemical compound OCCN1CCN=C1 GOHZKUSWWGUUNR-UHFFFAOYSA-N 0.000 description 2
- 239000005639 Lauric acid Substances 0.000 description 2
- NINIDFKCEFEMDL-UHFFFAOYSA-N Sulfur Chemical compound [S] NINIDFKCEFEMDL-UHFFFAOYSA-N 0.000 description 2
- TZHYBRCGYCPGBQ-UHFFFAOYSA-N [B].[N] Chemical group [B].[N] TZHYBRCGYCPGBQ-UHFFFAOYSA-N 0.000 description 2
- YUWBVKYVJWNVLE-UHFFFAOYSA-N [N].[P] Chemical compound [N].[P] YUWBVKYVJWNVLE-UHFFFAOYSA-N 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000010406 cathode material Substances 0.000 description 2
- 239000011247 coating layer Substances 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 125000000524 functional group Chemical group 0.000 description 2
- 238000003837 high-temperature calcination Methods 0.000 description 2
- 239000012535 impurity Substances 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 125000004433 nitrogen atom Chemical group N* 0.000 description 2
- 229940049964 oleate Drugs 0.000 description 2
- ZQPPMHVWECSIRJ-KTKRTIGZSA-N oleic acid Chemical compound CCCCCCCC\C=C/CCCCCCCC(O)=O ZQPPMHVWECSIRJ-KTKRTIGZSA-N 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000005245 sintering Methods 0.000 description 2
- 239000000243 solution Substances 0.000 description 2
- 238000001694 spray drying Methods 0.000 description 2
- 229910052717 sulfur Inorganic materials 0.000 description 2
- 239000011593 sulfur Substances 0.000 description 2
- OXFSTTJBVAAALW-UHFFFAOYSA-N 1,3-dihydroimidazole-2-thione Chemical class SC1=NC=CN1 OXFSTTJBVAAALW-UHFFFAOYSA-N 0.000 description 1
- FDQQNNZKEJIHMS-UHFFFAOYSA-N 3,4,5-trimethylphenol Chemical group CC1=CC(O)=CC(C)=C1C FDQQNNZKEJIHMS-UHFFFAOYSA-N 0.000 description 1
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 1
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical class [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- ZTOZIUYGNMLJES-UHFFFAOYSA-K [Li+].[C+4].[Fe+2].[O-]P([O-])([O-])=O Chemical compound [Li+].[C+4].[Fe+2].[O-]P([O-])([O-])=O ZTOZIUYGNMLJES-UHFFFAOYSA-K 0.000 description 1
- PFRUBEOIWWEFOL-UHFFFAOYSA-N [N].[S] Chemical compound [N].[S] PFRUBEOIWWEFOL-UHFFFAOYSA-N 0.000 description 1
- 238000005054 agglomeration Methods 0.000 description 1
- 230000002776 aggregation Effects 0.000 description 1
- 230000000903 blocking effect Effects 0.000 description 1
- UUOQPSKNKUVOBO-UHFFFAOYSA-N boric acid;1h-imidazole Chemical compound OB(O)O.C1=CNC=N1 UUOQPSKNKUVOBO-UHFFFAOYSA-N 0.000 description 1
- PWYPGEFOZYBWDP-UHFFFAOYSA-N boric acid;pyridine Chemical compound OB(O)O.C1=CC=NC=C1 PWYPGEFOZYBWDP-UHFFFAOYSA-N 0.000 description 1
- 229910052796 boron Inorganic materials 0.000 description 1
- 239000003575 carbonaceous material Substances 0.000 description 1
- 230000030833 cell death Effects 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000011258 core-shell material Substances 0.000 description 1
- 239000013078 crystal Substances 0.000 description 1
- 238000002425 crystallisation Methods 0.000 description 1
- 230000008025 crystallization Effects 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000003487 electrochemical reaction Methods 0.000 description 1
- 235000019441 ethanol Nutrition 0.000 description 1
- 125000005842 heteroatom Chemical group 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 230000037427 ion transport Effects 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- 238000011031 large-scale manufacturing process Methods 0.000 description 1
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- 239000007788 liquid Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- 230000007246 mechanism Effects 0.000 description 1
- GLVAUDGFNGKCSF-UHFFFAOYSA-N mercaptopurine Chemical class S=C1NC=NC2=C1NC=N2 GLVAUDGFNGKCSF-UHFFFAOYSA-N 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 230000005012 migration Effects 0.000 description 1
- 238000013508 migration Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 238000012545 processing Methods 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- HBCQSNAFLVXVAY-UHFFFAOYSA-N pyrimidine-2-thiol Chemical class SC1=NC=CC=N1 HBCQSNAFLVXVAY-UHFFFAOYSA-N 0.000 description 1
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- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps: 1) Mixing a lithium source, an iron source, a phosphorus source and a reducing agent in a solvent, and then drying and calcining to obtain a precursor; 2) Adding a carbon source and a nitrogen source into the precursor, then mixing in a solvent, and drying to obtain a mixture; 3) Calcining the mixture in an inert atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate material; the nitrogen source comprises at least one of 1, 3-dimethylhydroxyethyl-5, 5-dimethylhydantoin, 1, 3-dihydroxyethyl-5, 5-dimethylhydantoin, tri-hydroxyethyl isocyanurate, lauric acid hydroxyethyl imidazoline quaternary ammonium salt and oleic acid hydroxyethyl imidazoline. The preparation method is simple to operate, low in production cost and suitable for mass production, and the nitrogen-doped carbon-coated lithium iron phosphate with high multiplying power and cycle performance and high electron conduction ion transmission capacity is synthesized by doping nitrogen-containing heterocyclic molecules into the lithium iron phosphate anode material.
Description
Technical Field
The invention belongs to the technical field of lithium battery anode materials, and particularly relates to a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate anode material.
Background
Lithium iron phosphate is a popular power battery material at present, and is characterized by high specific energy, long service life and relatively low price. However, lithium iron phosphate batteries have a short cycle life and are prone to capacity fade and other problems. In order to improve the performance, a common means is to adopt a carbon-coated form, so that the contact area between lithium ions and electrode materials (lithium iron phosphate) is increased, more lithium ions participate in electrochemical reaction, and the internal resistance and the temperature rise of a battery are effectively reduced, so that the service life of the battery is prolonged. Although the carbon-coated form may enhance the performance of lithium iron phosphate, since the carbon material has poor conductive properties, it may have a blocking effect on lithium ion migration, thereby affecting the performance of the battery. This is particularly evident at low temperatures, which can easily cause cell death and affect the life of the cell.
The Chinese patent CN 201810959140.X discloses a nitrogen-doped carbon-coated lithium iron phosphate composite material and a preparation method thereof, wherein the composite material of the lithium iron phosphate is of a spherical core-shell structure, the thickness of the shell layer is 1-5 um, the coating amount is 1-5%, and the nitrogen doping content is 25-35%; the preparation method comprises the following steps: (1) preparing spherical ferric phosphate; (2) preparing a lithium iron phosphate precursor; (3) preparing an organic nitrogen source coating liquid; (4) preparing nitrogen-doped carbon-coated lithium iron phosphate. The organic nitrogen source is boron nitrogen source, nitrogen phosphorus source and nitrogen sulfur source, wherein the boron nitrogen source is selected from one or two of pyridine boric acid and imidazole boric acid; the nitrogen-phosphorus source is selected from N- (phosphonomethyl) iminodiacetic acid; the nitrogen and sulfur source is selected from one or more of mercaptoimidazole compounds, mercaptopyrimidine compounds and mercaptopurine compounds. However, the adopted organic nitrogen source contains boron, sulfur and other impurity elements, which is not beneficial to the improvement of the electrochemical performance of the lithium iron phosphate composite material; the coating process adopts liquid-solid phase reaction, spray drying is needed to obtain organic nitrogen source coated lithium iron phosphate precursor powder, the liquid-solid phase reaction process is complex, the subsequent separation is needed, the spray drying processing efficiency is low, the production cost is high, and the large-scale production is not facilitated.
Disclosure of Invention
Aiming at the defects of the prior art, the invention aims to provide a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which is simple to operate, low in production cost and suitable for mass production.
In order to achieve the above purpose, the present invention provides the following technical solutions:
the invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Mixing a lithium source, an iron source, a phosphorus source and a reducing agent in a solvent, and then drying and calcining to obtain a precursor;
(2) Adding a carbon source and a nitrogen source into the precursor obtained in the step (1), then mixing in a solvent, and drying to obtain a mixture;
(3) Calcining the mixture obtained in the step (2) in an inert atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material;
The nitrogen source comprises at least one of 1, 3-dimethylhydroxyethyl-5, 5-dimethylhydantoin, 1, 3-dihydroxyethyl-5, 5-dimethylhydantoin, tris (hydroxyethyl) isocyanurate (xylogen), lauric acid hydroxyethyl imidazoline quaternary ammonium salt and oleic acid hydroxyethyl imidazoline.
As a preferred embodiment, the lithium source includes at least one of lithium hydroxide, lithium acetate, lithium carbonate, and lithium chloride.
As a preferred embodiment, the iron source includes at least one of ferrous oxalate, ferrous acetate, feSO 4, ferric phosphate, iron powder, ferric oxide, and organic ferrous salts. Further preferably, the particle size of the iron powder is 4um.
As a preferred embodiment, the phosphorus source includes at least one of ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, lithium dihydrogen phosphate, and iron phosphate.
As a preferred embodiment, the reducing agent includes at least one of citric acid, glucose, sucrose, carbon graphite, super P, phenolic resin, and carbon black.
As a preferred embodiment, the carbon source includes at least one of citric acid, glucose, sucrose, carbon graphite, super P, phenolic resin, and carbon black.
As a preferred embodiment, the solvent includes at least one of ethanol, ethylene glycol, and deionized water.
In a preferred embodiment, in the step (1), the mixing mode is ball milling mixing, and the mixing time is 8-12 h, for example, 8h, 10h or 12h.
In a preferred embodiment, in the step (1), the calcining atmosphere is an inert atmosphere, for example, may be an Ar or N 2 atmosphere, and the calcining treatment is: calcining at 300-500 deg.c for 4-8 hr and then at 600-800 deg.c for 10-14 hr. When the sintering temperature is too low, the solid phase reaction is incomplete, the product contains Fe 3+ as an impurity, the crystallization degree is not high, small particles are easy to agglomerate together, the discharge specific capacity of the material is low, and the cycle performance is poor; when the sintering temperature is too high, secondary particles are generated in the material, an agglomeration phenomenon occurs, the specific surface area is small, crystal grains are easy to grow along with the temperature rise, the lithium ion diffusion path is increased, and the performance of the material is reduced.
As a preferred embodiment, in the step (2), the carbon source is 9 to 15wt%, for example, 9wt%, 11wt%, 12wt%, 13wt% or 15wt%.
In a preferred embodiment, in the step (2), the mixing mode is ball milling mixing, and the mixing time is 4-10 h, for example, may be 4h, 6h, 8h or 10h.
In a preferred embodiment, in the step (2), the drying temperature is 40 to 90 ℃, for example, 40 ℃, 60 ℃, 80 ℃ or 90 ℃.
In a preferred embodiment, in the step (3), the inert atmosphere is Ar or N 2 atmosphere.
In a preferred embodiment, in the step (3), the calcination is performed at 600 to 800 ℃ for 6 to 10 hours.
According to the invention, nitrogen-containing heterocyclic molecules are doped into the carbon coating layer on the surface of the lithium iron phosphate anode material in situ through high-temperature calcination, so that the electron conduction and ion transmission capacity of the carbon-coated lithium iron phosphate material is improved, and the cycle stability and rate capability of the carbon-coated lithium iron phosphate material are improved.
Compared with the prior art, the invention has the beneficial technical effects that:
The invention provides a nitrogen doping mechanism, which introduces nitrogen atoms into a lithium iron phosphate carbon coating layer. The nitrogen atoms in the nitrogen-doped carbon nanomaterial exist in the forms of hetero atoms, adsorption states, functional groups and the like, so that the conductivity and the metal characteristics of the nitrogen-doped carbon nanomaterial can be improved. In addition, the surface functional group of the nitrogen doped carbon nanomaterial can interact with phosphate ions of the lithium iron phosphate positive electrode material to form a chemical bond, so that the surface chemical property and structure of the positive electrode material are changed. These chemical actions can promote ion transport and electron conduction of the electrode material, and improve the electrochemical performance and cycle life of the lithium iron phosphate cathode material.
The invention provides a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which is mainly and innovated in that a high-performance lithium ion battery positive electrode material is simply and effectively synthesized, has higher electron conduction and ion transmission capacity and multiplying power performance, and has high capacity retention rate and excellent cycle stability after long-cycle test.
Drawings
For a clearer description of the technical solution of the implementation of the present invention, the following figures are briefly described. The following description of the drawings is merely exemplary of some embodiments of the present invention and may be practiced by those skilled in the art without undue burden, in light of the drawings and the actual manufacturing considerations.
FIG. 1 shows the rate capability (25 ℃ C.) of the samples of examples 1 to 5;
FIG. 2 shows the cycle properties (1C, 25 ℃) of the samples of examples 1 to 5;
FIG. 3 is a graph showing the cycling performance (1C, 25 ℃) of the nitrogen-doped coated lithium iron phosphate positive electrode materials of example 6 with different mass fractions of nitrogen sources.
Detailed Description
Detailed description the following examples are intended to further illustrate the present invention, but not to limit the scope of the invention.
Comparative example 1
The preparation method of the carbon-coated lithium iron phosphate positive electrode material comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3 and glucose, adding a proper amount of absolute ethyl alcohol, ball-milling for 12 hours (500 rpm), and drying at 60 ℃ for 12 hours after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding glucose as a carbon source, and controlling the mass fraction of the carbon source to be 12wt%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the carbon-coated lithium iron phosphate anode material (LFP/C-N 0).
Example 1
The invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3, 1, 3-dimethylhydroxyethyl-5, 5-dimethylhydantoin, adding a proper amount of absolute ethyl alcohol, ball milling for 12 hours (500 rpm), and drying at 60 ℃ for 12 hours after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding 1, 3-dimethylhydroxyethyl-5, 5-dimethylhydantoin as a nitrogen source and a carbon source, and controlling the mass fraction of the carbon source to be 12wt%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material (LFP/C-N 1).
Example 2
The invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3, 1, 3-dihydroxyethyl-5, 5-dimethylhydantoin, adding a proper amount of absolute ethyl alcohol, ball-milling for 12 hours (500 rpm), and drying at 60 ℃ for 12 hours after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding 1, 3-dihydroxyethyl-5, 5-dimethyl hydantoin as a nitrogen source and a carbon source, and controlling the mass fraction of the carbon source to be 12wt%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material (LFP/C-N 2).
Example 3
The invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3 and trihydroxyethyl isocyanurate (Saik), adding a proper amount of absolute ethyl alcohol, ball-milling for 12 hours (500 rpm), and drying at 60 ℃ for 12 hours after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding tris (hydroxyethyl) isocyanurate (Siek) as a nitrogen source and a carbon source, and controlling the mass fraction of the carbon source to be 12wt%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material (LFP/C-N 3).
Example 4
The invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3 and hydroxyethyl imidazoline quaternary ammonium salt of lauric acid, adding a proper amount of absolute ethyl alcohol, ball milling for 12 hours (500 rpm), and drying for 12 hours at 60 ℃ after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding hydroxyethyl imidazoline quaternary ammonium salt of lauric acid as a nitrogen source and a carbon source, and controlling the mass fraction of the carbon source to be 12wt%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material (LFP/C-N 4).
Example 5
The invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3 and hydroxyethyl imidazoline oleate, adding a proper amount of absolute ethyl alcohol, ball-milling for 12 hours (500 rpm), and drying for 12 hours at 60 ℃ after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding hydroxyethyl imidazoline oleate serving as a nitrogen source and a carbon source, and controlling the mass fraction of the carbon source to be 12wt%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material (LFP/C-N 5).
Example 6
The invention provides a preparation method of a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material, which comprises the following steps:
(1) Weighing a proper amount of FePO 4,Li2CO3 and trihydroxyethyl isocyanurate (Saik), adding a proper amount of absolute ethyl alcohol, ball-milling for 12 hours (500 rpm), and drying at 60 ℃ for 12 hours after finishing; placing the mixed raw materials into a tube furnace, pretreating for 4 hours at 300 ℃ in Ar gas atmosphere, then heating to 700 ℃, and calcining for 12 hours to obtain a precursor;
(2) Weighing a proper amount of lithium iron phosphate, adding tris (hydroxyethyl) isocyanurate (Siek) as a nitrogen source and a carbon source, and controlling the mass fraction of the carbon source to be 9%, 11%, 12%, 13% and 15%; adding 6ml of absolute ethyl alcohol, ball milling for 4 hours (500 rpm), and drying at 60 ℃ after finishing to obtain a mixture;
(3) And (3) placing the mixture into a tube furnace, and calcining at 600 ℃ for 6 hours in Ar gas atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material.
Application example
The lithium iron phosphate cathode materials prepared in examples 1 to 6 and comparative example 1 are applied to lithium batteries, and the specific process is as follows:
1. according to the following steps: super P Li: weighing a proper amount of raw materials according to a ratio of PVDF=97:1:2, and uniformly mixing the raw materials with NMP as a solvent, wherein the solid content is 50%;
2. Coating the pole piece, wherein the coating thickness is 100-150 micrometers, vacuum drying is carried out for 3-8 hours at the temperature of 90-150 ℃, and rolling is carried out until the compaction density is 2.1-2.7 g cm 3;
3. And assembling and buckling in a vacuum glove box, standing at 25 ℃ for 8-15 h, and testing.
Rate capability test
As shown in FIG. 1, LFP/C-N 0～5 is a graph comparing the rate performance of samples with examples 1 to 5, wherein glucose is used as a carbon source (C-N 0).
Cycle performance test
As shown in FIG. 2, LFP/C-N 0～5 is a graph comparing the cycle performance of samples with examples 1 to 5, wherein glucose is the carbon source (C-N 0).
As shown in FIG. 3, LFP/9～15％ C-N is a graph comparing sample cycle performance in example 6.
Table 1 comparison of the results of the performance tests of the lithium batteries prepared in examples 1 to 5 and comparative example 1
Conclusion of the invention: the carbon-coated lithium iron phosphate anode material remarkably improves the multiplying power performance and partial cycle performance after in-situ nitrogen doping by high-temperature calcination, simultaneously reduces the resistivity and greatly improves the performance of the lithium iron phosphate battery.
The above description is merely a preferred embodiment of the present invention, and the scope of the present invention is not limited to the above examples. Modifications and variations which would be obvious to those skilled in the art without departing from the spirit of the invention are also considered to be within the scope of the invention.
Claims (9)
1. The preparation method of the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material is characterized by comprising the following steps of:
(1) Mixing a lithium source, an iron source, a phosphorus source and a reducing agent in a solvent, and then drying and calcining to obtain a precursor;
(2) Adding a carbon source and a nitrogen source into the precursor obtained in the step (1), then mixing in a solvent, and drying to obtain a mixture;
(3) Calcining the mixture obtained in the step (2) in an inert atmosphere to obtain the nitrogen-doped carbon-coated lithium iron phosphate anode material;
The nitrogen source comprises at least one of 1, 3-dimethylhydroxyethyl-5, 5-dimethylhydantoin, 1, 3-dihydroxyethyl-5, 5-dimethylhydantoin, tris (hydroxyethyl) isocyanurate (xylogen), lauric acid hydroxyethyl imidazoline quaternary ammonium salt and oleic acid hydroxyethyl imidazoline.
2. The method for preparing a nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein the lithium source comprises at least one of lithium hydroxide, lithium acetate, lithium carbonate and lithium chloride;
The iron source comprises at least one of ferrous oxalate, ferrous acetate, feSO 4, ferric phosphate, iron powder, ferric oxide and organic ferrous salt;
The phosphorus source comprises at least one of ammonium hydrogen phosphate, diammonium hydrogen phosphate, ammonium phosphate, lithium dihydrogen phosphate and ferric phosphate;
The reducing agent comprises at least one of citric acid, glucose, sucrose, carbon graphite, super P, phenolic resin and carbon black;
the carbon source comprises at least one of citric acid, glucose, sucrose, carbon graphite, super P, phenolic resin and carbon black;
The solvent comprises at least one of ethanol, glycol and deionized water.
3. The preparation method of the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (1), the mixing mode is ball milling mixing, and the mixing time is 8-12 h.
4. The method for preparing a nitrogen-doped carbon coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (1), the calcining atmosphere is an inert atmosphere, preferably an Ar or N 2 atmosphere, and the calcining treatment is as follows: calcining at 300-500 deg.c for 4-8 hr and then at 600-800 deg.c for 10-14 hr.
5. The preparation method of the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (2), the mass fraction of the carbon source is 9-15 wt%.
6. The preparation method of the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (2), the mixing mode is ball milling mixing, and the mixing time is 4-10 h.
7. The method for preparing the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (2), the drying temperature is 40-90 ℃.
8. The method for preparing the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (3), the inert atmosphere is Ar or N 2 atmosphere.
9. The method for preparing the nitrogen-doped carbon-coated lithium iron phosphate positive electrode material according to claim 1, wherein in the step (3), the calcination temperature is 600-800 ℃ and the calcination time is 6-10 h.
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