CN118851135A - Preparation method and application of uniform carbon-coated lithium iron phosphate - Google Patents
Preparation method and application of uniform carbon-coated lithium iron phosphate Download PDFInfo
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- CN118851135A CN118851135A CN202411336862.1A CN202411336862A CN118851135A CN 118851135 A CN118851135 A CN 118851135A CN 202411336862 A CN202411336862 A CN 202411336862A CN 118851135 A CN118851135 A CN 118851135A
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- iron phosphate
- lithium iron
- lithium
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- carbon source
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 87
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 84
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 69
- 238000002360 preparation method Methods 0.000 title claims abstract description 11
- 239000002245 particle Substances 0.000 claims abstract description 65
- 238000000576 coating method Methods 0.000 claims abstract description 28
- 239000011248 coating agent Substances 0.000 claims abstract description 27
- 238000002156 mixing Methods 0.000 claims abstract description 27
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 23
- 239000005955 Ferric phosphate Substances 0.000 claims abstract description 19
- 229940032958 ferric phosphate Drugs 0.000 claims abstract description 19
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims abstract description 19
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 18
- 239000000463 material Substances 0.000 claims abstract description 18
- 239000002243 precursor Substances 0.000 claims abstract description 17
- 238000001694 spray drying Methods 0.000 claims abstract description 15
- 239000000725 suspension Substances 0.000 claims abstract description 14
- 239000002019 doping agent Substances 0.000 claims abstract description 8
- 238000001238 wet grinding Methods 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 7
- 239000012298 atmosphere Substances 0.000 claims abstract description 5
- 238000001354 calcination Methods 0.000 claims abstract description 5
- 239000011261 inert gas Substances 0.000 claims abstract description 3
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 28
- 238000010438 heat treatment Methods 0.000 claims description 16
- 229910052742 iron Inorganic materials 0.000 claims description 14
- 238000000034 method Methods 0.000 claims description 13
- 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
- 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 11
- 239000008103 glucose Substances 0.000 claims description 11
- 238000000498 ball milling Methods 0.000 claims description 9
- 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 8
- 229930006000 Sucrose Natural products 0.000 claims description 8
- 239000005720 sucrose Substances 0.000 claims description 8
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 7
- 239000002041 carbon nanotube Substances 0.000 claims description 7
- 229910021393 carbon nanotube Inorganic materials 0.000 claims description 7
- 238000003801 milling Methods 0.000 claims description 7
- 229910052698 phosphorus Inorganic materials 0.000 claims description 7
- 239000011574 phosphorus Substances 0.000 claims description 7
- 239000004576 sand Substances 0.000 claims description 7
- 239000007787 solid Substances 0.000 claims description 7
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 6
- 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 6
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 6
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 6
- 238000004321 preservation Methods 0.000 claims description 5
- CIWBSHSKHKDKBQ-JLAZNSOCSA-N Ascorbic acid Chemical compound OC[C@H](O)[C@H]1OC(=O)C(O)=C1O CIWBSHSKHKDKBQ-JLAZNSOCSA-N 0.000 claims description 4
- 239000002202 Polyethylene glycol Substances 0.000 claims description 4
- 229910002804 graphite Inorganic materials 0.000 claims description 4
- 239000010439 graphite Substances 0.000 claims description 4
- AMWRITDGCCNYAT-UHFFFAOYSA-L hydroxy(oxo)manganese;manganese Chemical compound [Mn].O[Mn]=O.O[Mn]=O AMWRITDGCCNYAT-UHFFFAOYSA-L 0.000 claims description 4
- URLJKFSTXLNXLG-UHFFFAOYSA-N niobium(5+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[Nb+5].[Nb+5] URLJKFSTXLNXLG-UHFFFAOYSA-N 0.000 claims description 4
- 229920001223 polyethylene glycol Polymers 0.000 claims description 4
- 238000005245 sintering Methods 0.000 claims description 3
- 229930091371 Fructose Natural products 0.000 claims description 2
- 239000005715 Fructose Substances 0.000 claims description 2
- RFSUNEUAIZKAJO-ARQDHWQXSA-N Fructose Chemical compound OC[C@H]1O[C@](O)(CO)[C@@H](O)[C@@H]1O RFSUNEUAIZKAJO-ARQDHWQXSA-N 0.000 claims description 2
- 229920002472 Starch Polymers 0.000 claims description 2
- XHCLAFWTIXFWPH-UHFFFAOYSA-N [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] Chemical compound [O-2].[O-2].[O-2].[O-2].[O-2].[V+5].[V+5] XHCLAFWTIXFWPH-UHFFFAOYSA-N 0.000 claims description 2
- 239000006230 acetylene black Substances 0.000 claims description 2
- 229960005070 ascorbic acid Drugs 0.000 claims description 2
- 235000010323 ascorbic acid Nutrition 0.000 claims description 2
- 239000011668 ascorbic acid Substances 0.000 claims description 2
- 239000001913 cellulose Substances 0.000 claims description 2
- 229920002678 cellulose Polymers 0.000 claims description 2
- REKWWOFUJAJBCL-UHFFFAOYSA-L dilithium;hydrogen phosphate Chemical compound [Li+].[Li+].OP([O-])([O-])=O REKWWOFUJAJBCL-UHFFFAOYSA-L 0.000 claims description 2
- 239000012530 fluid Substances 0.000 claims description 2
- 229910021389 graphene Inorganic materials 0.000 claims description 2
- 229910001386 lithium phosphate Inorganic materials 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
- 229910000484 niobium oxide Inorganic materials 0.000 claims description 2
- 239000008107 starch Substances 0.000 claims description 2
- 235000019698 starch Nutrition 0.000 claims description 2
- OGIDPMRJRNCKJF-UHFFFAOYSA-N titanium oxide Inorganic materials [Ti]=O OGIDPMRJRNCKJF-UHFFFAOYSA-N 0.000 claims description 2
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 2
- 229910001935 vanadium oxide Inorganic materials 0.000 claims description 2
- 229910000398 iron phosphate Inorganic materials 0.000 claims 4
- 238000010298 pulverizing process Methods 0.000 claims 2
- 238000004519 manufacturing process Methods 0.000 claims 1
- 239000007774 positive electrode material Substances 0.000 claims 1
- 238000005516 engineering process Methods 0.000 abstract description 3
- 238000009826 distribution Methods 0.000 abstract description 2
- 239000002105 nanoparticle Substances 0.000 abstract description 2
- 102220043159 rs587780996 Human genes 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 9
- 238000000227 grinding Methods 0.000 description 6
- 239000013078 crystal Substances 0.000 description 4
- 238000009792 diffusion process Methods 0.000 description 4
- 238000001035 drying Methods 0.000 description 4
- 239000000203 mixture Substances 0.000 description 4
- 239000012299 nitrogen atmosphere Substances 0.000 description 4
- 239000000843 powder Substances 0.000 description 4
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 239000010405 anode material Substances 0.000 description 3
- 238000005253 cladding Methods 0.000 description 3
- 238000005056 compaction Methods 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 150000002500 ions Chemical class 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000007599 discharging Methods 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 238000003837 high-temperature calcination Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- ZKATWMILCYLAPD-UHFFFAOYSA-N niobium pentoxide Inorganic materials O=[Nb](=O)O[Nb](=O)=O ZKATWMILCYLAPD-UHFFFAOYSA-N 0.000 description 2
- 230000000630 rising effect Effects 0.000 description 2
- 238000001228 spectrum Methods 0.000 description 2
- 239000004408 titanium dioxide Substances 0.000 description 2
- 239000006245 Carbon black Super-P Substances 0.000 description 1
- 229910013870 LiPF 6 Inorganic materials 0.000 description 1
- FYYHWMGAXLPEAU-UHFFFAOYSA-N Magnesium Chemical compound [Mg] FYYHWMGAXLPEAU-UHFFFAOYSA-N 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 239000004743 Polypropylene Substances 0.000 description 1
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 description 1
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000013590 bulk material Substances 0.000 description 1
- 238000007600 charging Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000010281 constant-current constant-voltage charging Methods 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 230000007613 environmental effect Effects 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
- 230000008595 infiltration Effects 0.000 description 1
- 238000001764 infiltration Methods 0.000 description 1
- 229910052749 magnesium Inorganic materials 0.000 description 1
- 239000011777 magnesium Substances 0.000 description 1
- 230000014759 maintenance of location Effects 0.000 description 1
- WPBNNNQJVZRUHP-UHFFFAOYSA-L manganese(2+);methyl n-[[2-(methoxycarbonylcarbamothioylamino)phenyl]carbamothioyl]carbamate;n-[2-(sulfidocarbothioylamino)ethyl]carbamodithioate Chemical compound [Mn+2].[S-]C(=S)NCCNC([S-])=S.COC(=O)NC(=S)NC1=CC=CC=C1NC(=S)NC(=O)OC WPBNNNQJVZRUHP-UHFFFAOYSA-L 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- 238000002715 modification method Methods 0.000 description 1
- -1 polypropylene Polymers 0.000 description 1
- 229920001155 polypropylene Polymers 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 239000002002 slurry Substances 0.000 description 1
- 239000002904 solvent Substances 0.000 description 1
- 239000010936 titanium Substances 0.000 description 1
- 229910052719 titanium Inorganic materials 0.000 description 1
- 238000001291 vacuum drying Methods 0.000 description 1
- 229910052720 vanadium Inorganic materials 0.000 description 1
- GPPXJZIENCGNKB-UHFFFAOYSA-N vanadium Chemical compound [V]#[V] GPPXJZIENCGNKB-UHFFFAOYSA-N 0.000 description 1
- 229910052726 zirconium Inorganic materials 0.000 description 1
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Abstract
The invention relates to the technical field of lithium batteries, in particular to a preparation method and application of uniform carbon-coated lithium iron phosphate, and the preparation method comprises the following steps: s1, adding ferric phosphate, a lithium source, an organic carbon source and a doping agent into pure water for grading wet grinding to obtain a uniformly mixed suspension; s2, performing spray drying on the obtained suspension to obtain a precursor with uniform granularity; s3, calcining the obtained precursor in an inert gas atmosphere to obtain primary lithium iron phosphate with uniform phase; s4, mixing and coating the obtained primary lithium iron phosphate and a mixed carbon source, and then carrying out grading crushing to obtain the uniformly coated and particle-graded lithium iron phosphate material. Firstly, adopting a grading wet grinding technology to enable material particles to be nano-sized and have uniform particle size distribution; secondly, a high Wen Baofu machine (VCJ) is used, so that the carbon coating is uniform and the coating thickness is uniform; finally, a grading crushing mode is adopted, so that the material particles are graded and closely stacked.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a preparation method and application of uniform carbon-coated lithium iron phosphate.
Background
The lithium iron phosphate anode material is the most safe power battery material which is widely applied to various fields of portable electronic equipment, power batteries and energy storage power stations because of the advantages of long charge and discharge platform, stable property, low price, environmental friendliness and the like. However, LFP has the disadvantages of low lithium ion diffusion rate, low electron conductivity, low tap density, and the like, resulting in extremely poor high rate performance.
In order to improve the low-temperature and rate performance of lithium iron phosphate, the prior art optimizes the electron and ion conductivity by means of element doping modification or carbon coating. For example, the patent CN 202211649263.6 is doped with one or more of zirconium, titanium, manganese, magnesium, vanadium and their compounds, and the doping forms crystal defects to improve the ionic conductivity of the bulk material; in the patent No. CN 117819509A, a porous carbon coating method is adopted to inhibit the growth of lithium iron phosphate crystal grains, control the particle size of lithium iron phosphate and shorten the diffusion path of lithium ions. The method only forms a conductive network through carbon cladding and forms crystal defects through doping, improves ionic and electronic conductivity of a material body, and can not achieve ideal state for better improving compaction density and multiplying power performance of the material. Therefore, there is an urgent need to construct a new method to solve the above problems.
Disclosure of Invention
In view of the above, the invention aims to provide a preparation method and application of uniform carbon-coated lithium iron phosphate, and the invention firstly adopts a grading wet grinding technology to enable material particles to be nano-sized and uniformly distributed in granularity, reduce the particle size, shorten the Li + diffusion distance and further remarkably improve the rate capability of LFP; secondly, a high Wen Baofu machine (VCJ) is used, so that the carbon is uniformly coated, the coating thickness is uniform, a good conductive network is formed among particles, and the transfer rate of electrons is further promoted; finally, a grading crushing mode is adopted, so that the material particles are graded and closely stacked, the close stacking of large and small particles is realized, and the compaction density of the LFP is remarkably improved.
Based on the above object, the invention provides a preparation method of uniform carbon-coated lithium iron phosphate, comprising the following steps:
s1, adding ferric phosphate, a lithium source, an organic carbon source and a doping agent into pure water for grading wet grinding to obtain a uniformly mixed suspension;
S2, performing spray drying on the obtained suspension to obtain a precursor with uniform granularity;
S3, calcining the obtained precursor in an inert gas atmosphere to obtain primary lithium iron phosphate with uniform phase;
S4, mixing and coating the obtained primary lithium iron phosphate and a mixed carbon source, and then carrying out grading crushing to obtain the uniformly coated and particle-graded lithium iron phosphate material.
The ratio of the ferric phosphate to the lithium source in the S1 is 1-1.05:1 according to the molar ratio of lithium to iron, the molar ratio of iron to phosphorus in the ferric phosphate is 0.96-1:1, the addition of the organic carbon source is 5-15% of the mass of the ferric phosphate, and the addition of the doping agent is 0.1-0.5% of the mass of the ferric phosphate. Preferably, the proportion of the ferric phosphate and the lithium source is 1.02-1.04:1 according to the molar ratio of lithium to iron, the molar ratio of iron to phosphorus in the ferric phosphate is 0.96-0.98:1, the addition of the organic carbon source is 8-12% of the mass of the ferric phosphate, and the addition of the doping agent is 0.1-0.3% of the mass of the ferric phosphate.
The lithium source is one or more of lithium phosphate, lithium carbonate, lithium hydroxide, lithium hydrogen phosphate and lithium dihydrogen phosphate; the organic carbon source is one or more of ascorbic acid, polyethylene glycol, sucrose, glucose, citric acid, fructose, cellulose and starch; the doping agent is one or more of titanium oxide, niobium oxide, vanadium oxide and manganese oxide.
The grading wet grinding is to perform wet ball milling firstly and then wet sand milling, wherein the solid content is 20-40%, the ball milling particle size d50=1-1.5 μm, and the sand milling particle size d50=100-500 nm. Preferably, the solid content is 30-35%, the ball milling particle size d50=1-1.2 μm and the sand milling particle size d50=200-400 nm.
And S2, adopting centrifugal or two-fluid spray drying, wherein the inlet temperature of the spray drying is 190-210 ℃, the outlet temperature is 90-110 ℃, the feeding rate is 20-50mL/min, and the particle size D50=5-20 μm of the precursor of the spray drying. Preferably, the spray-dried precursor particle size d50=8-15 μm.
The calcination in S3 adopts high-temperature calcination, the high-temperature calcination procedure is that the presintering temperature is 300-600 ℃, and the heat preservation time is 2-5h; the sintering temperature is 600-750 ℃, the heat preservation time is 10-15h, wherein the inert atmosphere is N 2 or Ar, and the heating rate is 1-10 ℃/min. Preferably, the presintering temperature is 350-550 ℃, and the heat preservation time is 3-4h. Preferably, the sintering temperature is 650-750 ℃, the heat preservation time is 10-15h, and the heating rate is 5-8 ℃/min.
And S4, mixing an organic carbon source and an inorganic carbon source, wherein the organic carbon source is one or more of glucose, sucrose, polyethylene glycol and citric acid, the inorganic carbon source is one or more of graphite, carbon nano tubes, graphene and acetylene black, the addition amount of the mixed carbon source is 1-5% of the mass of the primary lithium iron phosphate, and the mixing mass ratio is that the organic carbon source is inorganic carbon source=9-1:1-9. Preferably, the addition amount of the mixed carbon source is 3-4% of the mass of the primary lithium iron phosphate, and the mixing mass ratio is that the organic carbon source to the inorganic carbon source is 8-2:2-8.
And S4, coating by adopting a high Wen Baofu machine, wherein the mixing rotating speed of the high Wen Baofu machine is 100-500rpm/min, the heating temperature is 300-700 ℃, and the mixing time is 1-5h. Preferably, the mixing speed of the high Wen Baofu machine is 200-400rpm/min, the heating temperature is 300-600 ℃, and the mixing time is 2-4h.
The equipment for classifying and crushing in S4 is a mechanical superfine crusher or an airflow superfine crusher, wherein the large-particle lithium iron phosphate is obtained after classifying and crushing, the particle size D50=500-1000 nm and the particle size D50=50-500 nm of the small-particle lithium iron phosphate are obtained, and the mass ratio of the large-particle lithium iron phosphate to the small-particle lithium iron phosphate is 1-9:9-1. Preferably, the particle size d50=600-800 nm of the particulate lithium iron phosphate, the particle size d50=100-300 nm of the small particulate lithium iron phosphate, and the mass ratio of the large particulate lithium iron phosphate to the small particulate lithium iron phosphate is preferably 4-6:6-4.
The invention also provides uniform carbon-coated lithium iron phosphate, which is prepared by adopting the preparation method of the uniform carbon-coated lithium iron phosphate.
The invention also provides application of the lithium iron phosphate prepared by the preparation method of the uniform carbon-coated lithium iron phosphate in a battery anode material.
The invention has the beneficial effects that:
The invention adopts a grading wet grinding technology, so that the slurry is mixed more uniformly, the particle size distribution is more uniform while the particles are nanocrystallized, and the multiplying power performance of the material is effectively improved by reducing the particle size of the particles, shortening the diffusion distance of lithium ions and increasing the infiltration area of electrolyte.
According to the invention, a carbon coating and ion doping modification method is adopted, a conductive network is formed through carbon coating, crystal defects are formed through doping, and the ion and electron conductivity of a material body is improved, so that the rate capability of the material is effectively improved.
According to the invention, in-situ doping combined with organic-inorganic carbon sources is adopted, atomic-level carbon generated by decomposition of the organic carbon sources can be uniformly coated on the surface of the material, so that the growth of primary particles of lithium iron phosphate is inhibited, the morphology of the particles is more full and the size of the particles is more uniform, the improvement of the circulation performance is facilitated, in addition, the internal resistance of the material is reduced due to doping of the inorganic carbon sources, and the conductivity of the material is also greatly improved.
The invention adopts a grading crushing mode, so that LFP particles with particle grading are closely contacted, the compaction density of the material can be improved, and the multiplying power performance of the material can be improved.
The invention uses a high Wen Baofu machine (VCJ) to ensure that the carbon coating is uniform and the coating thickness is uniform, and good conductive network is formed among particles, thereby promoting the transfer rate of electrons.
Drawings
In order to more clearly illustrate the invention or the technical solutions of the prior art, the drawings which are used in the description of the embodiments or the prior art will be briefly described, it being obvious that the drawings in the description below are only of the invention and that other drawings can be obtained from them without inventive effort for a person skilled in the art.
FIG. 1 is an XRD pattern of lithium iron phosphate prepared in example 1;
FIG. 2 is a TEM spectrum of lithium iron phosphate prepared in example 1;
fig. 3 is a graph showing a comparison of first charge and discharge curves of lithium iron phosphate prepared in example 1 and comparative example 1.
Detailed Description
The present invention will be further described in detail with reference to specific embodiments in order to make the objects, technical solutions and advantages of the present invention more apparent.
It is to be noted that unless otherwise defined, technical or scientific terms used herein should be taken in a general sense as understood by one of ordinary skill in the art to which the present invention belongs.
Example 1
(1) Mixing lithium carbonate and ferric phosphate (molar ratio of iron to phosphorus=0.968:1) according to the molar ratio of lithium to iron of 1.025:1, and adding glucose and titanium dioxide respectively according to 10% and 0.15% of the mass of the ferric phosphate; adding pure water according to the solid content of 35 percent for graded grinding, firstly ball-milling to the granularity D50=1 mu m, and then transferring to the sand milling to the granularity D50=350 nm to obtain a uniformly mixed suspension;
(2) Carrying out centrifugal spray drying on the uniformly mixed suspension, wherein the temperature of a feed inlet is 200 ℃, the temperature of a discharge outlet is 100 ℃, the feed rate is 30 mL/min, and the drying granularity D50=15 mu m is controlled to obtain a precursor with uniform granularity;
(3) The dried precursor reaches a constant temperature of 500 ℃ for 4h at a heating rate of 5 ℃/min under an N 2 atmosphere, then reaches a constant temperature of 700 ℃ for 10 h at a heating rate of 5 ℃/min to obtain calcined gray black powder, and then is crushed to obtain primary lithium iron phosphate with uniform phase;
(4) Adding primary lithium iron phosphate into a high-temperature coating machine (VCJ), adding a mixed carbon source (glucose: carbon nano tube=8:2) according to 3% of the mass of the primary lithium iron phosphate for mixed coating, wherein the mixing speed is 350 rpm/min, the heating temperature is 500 ℃, the mixing time is 3h, after the mixed coating is finished, the mixture is subjected to graded crushing, the particle size of large particles is controlled to be 600 nm, the particle size of small particles is controlled to be 200 nm, and the mass ratio of the large-particle lithium iron phosphate to the small-particle lithium iron phosphate is 4:6, so that the uniformly coated and particle-graded lithium iron phosphate is obtained.
Example 2
(1) Mixing lithium carbonate and ferric phosphate (molar ratio of iron to phosphorus=0.965:1) according to the molar ratio of lithium to iron of 1.03:1, and adding sucrose and niobium pentoxide respectively according to 12% and 0.2% of the mass of the ferric phosphate; adding pure water according to the solid content of 30 percent for graded grinding, firstly ball-milling to the granularity D50=1.2 mu m, and then transferring to the grinding to the granularity D50=300 nm to obtain a uniformly mixed suspension;
(2) Carrying out centrifugal spray drying on the uniformly mixed suspension, wherein the temperature of a feed inlet is 210 ℃, the temperature of a discharge outlet is 100 ℃, the feed rate is 35 mL/min, and the drying granularity D50=14 mu m is controlled to obtain a precursor with uniform granularity;
(3) The dried precursor reaches a constant temperature of 6 h at 400 ℃ at a heating rate of 6 ℃/min under an N 2 atmosphere, then reaches a constant temperature of 12 h at 680 ℃ at a heating rate of 6 ℃/min to obtain calcined gray black powder, and then is crushed to obtain primary lithium iron phosphate with uniform phase;
(4) Adding primary lithium iron phosphate into a high-temperature coating machine (VCJ), adding a mixed carbon source (sucrose: carbon nano tube=6:4) according to the mass of the primary lithium iron phosphate for mixed coating, wherein the mixing rotating speed is 400 rpm/min, the heating temperature is 600 ℃, the mixing time is 2h, after the mixed coating is finished, the mixture is subjected to classified crushing, the particle size of large particles is 500 nm, the particle size of small particles is 300 nm, and the mass ratio of the large-particle lithium iron phosphate to the small-particle lithium iron phosphate is 5:5, so that the uniformly coated and particle-graded lithium iron phosphate is obtained.
Example 3
(1) Mixing lithium carbonate and ferric phosphate (molar ratio of iron to phosphorus=0.971:1) according to the molar ratio of lithium to iron of 1.025:1, and adding glucose and niobium pentoxide respectively according to 8% and 0.1% of the mass of the ferric phosphate; adding pure water according to the solid content of 32%, carrying out graded grinding, firstly ball milling to the granularity D50=1 mu m, and then transferring to sand milling to the granularity D50=200 nm to obtain a uniformly mixed suspension;
(2) Carrying out centrifugal spray drying on the uniformly mixed suspension, wherein the temperature of a feed inlet is 200 ℃, the temperature of a discharge outlet is 100 ℃, the feed rate is 40 mL/min, and the drying granularity D50=12 mu m is controlled to obtain a precursor with uniform granularity;
(3) The dried precursor is heated to 550 ℃ at a heating rate of 6 ℃/min for 2 h under N 2 atmosphere, then heated to 720 ℃ at a heating rate of 6 ℃/min for 8 h to obtain calcined gray black powder, and then crushed to obtain primary lithium iron phosphate with uniform phase;
(4) Adding primary lithium iron phosphate into a high-temperature coating machine (VCJ), adding a mixed carbon source (glucose: graphite=7:3) according to the mass of the primary lithium iron phosphate for mixed coating, wherein the mixing rotating speed is 400 rpm/min, the heating temperature is 550 ℃, the mixing time is 3h, after the mixed coating is finished, the mixture is subjected to classified crushing, the particle size of large particles is controlled to be 600 nm, the particle size of small particles is controlled to be 300 nm, and the mass ratio of the large-particle lithium iron phosphate to the small-particle lithium iron phosphate is 6:4, so that the uniformly coated and particle-graded lithium iron phosphate is obtained.
Example 4
(1) Mixing lithium carbonate and ferric phosphate (molar ratio of iron to phosphorus=0.985:1) according to the molar ratio of lithium to iron of 1.03:1, and adding sucrose and titanium dioxide respectively according to 10% and 0.2% of the mass of the ferric phosphate; adding pure water according to the solid content of 35 percent for graded grinding, firstly ball-milling to the granularity D50=1.5 mu m, and then transferring to the grinding to the granularity D50=250 nm to obtain a uniformly mixed suspension;
(2) Centrifugal spray drying is carried out on the uniformly mixed suspension, the temperature of a feed inlet is 210 ℃, the temperature of a discharge outlet is 110 ℃, the feed rate is 25 mL/min, and the drying granularity D50=15 mu m is controlled to obtain a precursor with uniform granularity;
(3) The dried precursor reaches a constant temperature of 5h at a temperature rising rate of 8 ℃/min to 500 ℃ under an N 2 atmosphere, then reaches a constant temperature of 12 h at a temperature rising rate of 8 ℃/min to 700 ℃ to obtain calcined gray black powder, and then is crushed to obtain primary lithium iron phosphate with uniform phase;
(4) Adding primary lithium iron phosphate into a high-temperature coating machine (VCJ), adding a mixed carbon source (sucrose: graphite=8:2) according to the mass of the primary lithium iron phosphate for mixed coating, wherein the mixing rotating speed is 400 rpm/min, the heating temperature is 600 ℃, the mixing time is 4h, after the mixed coating is finished, the mixture is subjected to classified crushing, the particle size of large particles is controlled to be 500 nm, the particle size of small particles is controlled to be 200 nm, and the mass ratio of the large-particle lithium iron phosphate to the small-particle lithium iron phosphate is 9:2, so that the uniformly coated and particle-graded lithium iron phosphate is obtained.
Comparative example 1
(1), (2) And (3) are the same as in example 1;
(4) The 3% mixed carbon source (glucose: carbon nanotube molar ratio = 8:2) was replaced with 3% glucose as the sole carbon source, with the other conditions unchanged.
Comparative example 2
(1), (2) And (3) are the same as in example 1;
(4) The 3% mixed carbon source (glucose: carbon nanotubes molar ratio = 8:2) was replaced with 3% carbon nanotubes as the sole carbon source, with the other conditions unchanged.
Comparative example 3
(1), (2) And (3) are the same as in example 1;
(4) The hybrid cladding was performed without using a high temperature cladding machine (VCJ).
FIG. 1 is an XRD pattern of lithium iron phosphate prepared in example 1, and as can be seen, the XRD pattern of example 1 is consistent with that of a standard PDF card, indicating that the lithium iron phosphate prepared by the method of the invention is pure phase and free of impurities; fig. 2 is a TEM spectrum of the lithium iron phosphate prepared in example 1, from which it can be seen that the lithium iron phosphate prepared in example 1 has a uniform and moderate thickness of carbon coating; fig. 3 is a graph showing the first charge and discharge curves of the lithium iron phosphate prepared in example 1 and comparative example 1, and it can be seen from the graph that example 1 has a longer charge and discharge platform and a higher specific capacity than comparative example 1, and illustrates the potential performance of the lithium iron phosphate prepared by the method of the invention with high capacity and high rate.
Dispersing the lithium iron phosphate anode materials prepared in examples 1-4 and comparative examples 1-3, super-P and PVDF in NMP according to a mass ratio of 8:1:1, uniformly dispersing, coating on aluminum foil, and vacuum drying to obtain an anode pole piece, wherein the electrolyte is LiPF 6 of 1 mol/L, the solvent volume ratio is EC:DMC:EMC=1:1:1 (volume ratio), the diaphragm is a polypropylene film, and the metal lithium piece is a negative electrode, and assembling the anode pole piece into the electricity-buckling half battery. The test voltage range is 2.0V-3.75V, the constant-current constant-voltage charging mode is adopted to charge to 3.75V, the constant-current discharging mode is adopted to discharge to 2.0V, and the charging and discharging currents are 0.2C, 0.5C and 1C respectively circulated for 3 circles; and then the 3C charge-discharge current is used for circulating 500 circles, and the cut-off voltage condition is the same as that of 0.2C. The test results are shown in table 1 below:
From the data in the table above, it can be known that the specific capacity of the lithium iron phosphate prepared by the method of the invention is obviously higher than that of the lithium iron phosphate of the comparative example, and the rate capability is also obviously better than that of the comparative example, the specific capacity of the lithium iron phosphate of the invention at 0.2C can reach 159.6 mAh/g, and meanwhile, the capacity retention rate after 500 circles of 3C circulation is as high as 98.7%.
Those of ordinary skill in the art will appreciate that: the discussion of any of the embodiments above is merely exemplary and is not intended to suggest that the scope of the invention is limited to these examples; the technical features of the above embodiments or in the different embodiments may also be combined within the idea of the invention, the steps may be implemented in any order and there are many other variations of the different aspects of the invention as described above, which are not provided in detail for the sake of brevity. Any omission, modification, equivalent replacement, improvement, etc. of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The preparation method of the uniform carbon-coated lithium iron phosphate is characterized by comprising the following steps of:
s1, adding ferric phosphate, a lithium source, an organic carbon source and a doping agent into pure water for grading wet grinding to obtain a uniformly mixed suspension;
S2, performing spray drying on the obtained suspension to obtain a precursor with uniform granularity;
S3, calcining the obtained precursor in an inert gas atmosphere to obtain primary lithium iron phosphate with uniform phase;
S4, mixing and coating the obtained primary lithium iron phosphate and a mixed carbon source, and then carrying out grading crushing to obtain the uniformly coated and particle-graded lithium iron phosphate material.
2. The method for preparing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the ratio of the iron phosphate to the lithium source in S1 is 1-1.05:1 according to the molar ratio of lithium to iron, the molar ratio of iron to phosphorus in the iron phosphate is 0.96-1:1, the addition amount of the organic carbon source is 5-15% of the mass of the iron phosphate, and the addition amount of the dopant is 0.1-0.5% of the mass of the iron phosphate.
3. The method for preparing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the lithium source is one or more of lithium phosphate, lithium carbonate, lithium hydroxide, dilithium phosphate, and lithium dihydrogen phosphate; the organic carbon source is one or more of ascorbic acid, polyethylene glycol, sucrose, glucose, citric acid, fructose, cellulose and starch; the doping agent is one or more of titanium oxide, niobium oxide, vanadium oxide and manganese oxide.
4. The method for preparing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the classified wet grinding is performed by wet ball milling and then wet sand milling, wherein the solid content is 20-40%, the ball milling particle diameter d50=1-1.5 μm, and the sand milling particle diameter d50=100-500 nm.
5. The method for preparing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the spray drying in S2 is centrifugal or two-fluid spray drying, the spray drying inlet temperature is 190-210 ℃, the spray drying outlet temperature is 90-110 ℃, the feeding rate is 20-50mL/min, and the spray drying precursor particle size d50=5-20 μm.
6. The method for preparing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the calcination in S3 is performed at a high temperature of 300-600 ℃ for 2-5 hours; the sintering temperature is 600-750 ℃, the heat preservation time is 10-15h, wherein the inert atmosphere is N 2 or Ar, and the heating rate is 1-10 ℃/min.
7. The preparation method of the uniform carbon-coated lithium iron phosphate according to claim 1, wherein the mixed carbon source in the step S4 is formed by mixing an organic carbon source and an inorganic carbon source, wherein the organic carbon source is one or more of glucose, sucrose, polyethylene glycol and citric acid, the inorganic carbon source is one or more of graphite, carbon nano tubes, graphene and acetylene black, the addition amount of the mixed carbon source is 1-5% of the mass of the primary lithium iron phosphate, and the mixing mass ratio is that the organic carbon source is inorganic carbon source=9-1:1-9.
8. The method for preparing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the mixing coating in S4 is carried out by adopting a high Wen Baofu machine, the mixing rotating speed of the high Wen Baofu machine is 100-500rpm/min, the heating temperature is 300-700 ℃, and the mixing time is 1-5h.
9. The method for producing uniform carbon-coated lithium iron phosphate according to claim 1, wherein the equipment for classification pulverization in S4 is a mechanical ultrafine pulverizer or an air flow ultrafine pulverizer, wherein the particle diameter d50=500-1000 nm of the large-particle lithium iron phosphate and the particle diameter d50=50-500 nm of the small-particle lithium iron phosphate are obtained after classification pulverization, and the mass ratio of the large-particle lithium iron phosphate to the small-particle lithium iron phosphate is 1-9:9-1.
10. Use of the lithium iron phosphate prepared by the method for preparing uniform carbon-coated lithium iron phosphate according to any one of claims 1 to 9 in a positive electrode material of a battery.
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