CN115744862A - High-energy-density ordered nano spherical lithium iron phosphate and preparation method thereof - Google Patents
High-energy-density ordered nano spherical lithium iron phosphate and preparation method thereof Download PDFInfo
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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 117
- 238000002360 preparation method Methods 0.000 title claims abstract description 33
- 239000002245 particle Substances 0.000 claims abstract description 186
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 92
- 229910000398 iron phosphate Inorganic materials 0.000 claims abstract description 68
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 66
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 66
- 239000002002 slurry Substances 0.000 claims abstract description 66
- 238000002156 mixing Methods 0.000 claims abstract description 35
- 239000000463 material Substances 0.000 claims abstract description 32
- 238000006243 chemical reaction Methods 0.000 claims abstract description 28
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 19
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 19
- 238000001694 spray drying Methods 0.000 claims abstract description 16
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims abstract description 12
- 229910001416 lithium ion Inorganic materials 0.000 claims abstract description 12
- 229910044991 metal oxide Inorganic materials 0.000 claims abstract description 6
- 150000004706 metal oxides Chemical class 0.000 claims abstract description 6
- 238000010438 heat treatment Methods 0.000 claims description 36
- 239000002243 precursor Substances 0.000 claims description 32
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 26
- VCJMYUPGQJHHFU-UHFFFAOYSA-N iron(3+);trinitrate Chemical compound [Fe+3].[O-][N+]([O-])=O.[O-][N+]([O-])=O.[O-][N+]([O-])=O VCJMYUPGQJHHFU-UHFFFAOYSA-N 0.000 claims description 26
- 239000005955 Ferric phosphate Substances 0.000 claims description 23
- 229940032958 ferric phosphate Drugs 0.000 claims description 23
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 23
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 18
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims description 18
- 238000000034 method Methods 0.000 claims description 18
- 238000005245 sintering Methods 0.000 claims description 15
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims description 14
- 239000011574 phosphorus Substances 0.000 claims description 14
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 13
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 12
- 238000000227 grinding Methods 0.000 claims description 12
- 238000001291 vacuum drying Methods 0.000 claims description 10
- 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 9
- 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 9
- 238000001914 filtration Methods 0.000 claims description 9
- 239000008103 glucose Substances 0.000 claims description 9
- 239000007791 liquid phase Substances 0.000 claims description 9
- 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
- 229910052757 nitrogen Inorganic materials 0.000 claims description 9
- 239000004408 titanium dioxide Substances 0.000 claims description 9
- 238000005406 washing Methods 0.000 claims description 9
- DBMJMQXJHONAFJ-UHFFFAOYSA-M Sodium laurylsulphate Chemical compound [Na+].CCCCCCCCCCCCOS([O-])(=O)=O DBMJMQXJHONAFJ-UHFFFAOYSA-M 0.000 claims description 8
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 claims description 8
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 8
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 8
- GRYLNZFGIOXLOG-UHFFFAOYSA-N Nitric acid Chemical compound O[N+]([O-])=O GRYLNZFGIOXLOG-UHFFFAOYSA-N 0.000 claims description 7
- 229910017604 nitric acid Inorganic materials 0.000 claims description 7
- 239000000654 additive Substances 0.000 claims description 6
- 230000000996 additive effect Effects 0.000 claims description 6
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 6
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 6
- RUTXIHLAWFEWGM-UHFFFAOYSA-H iron(3+) sulfate Chemical compound [Fe+3].[Fe+3].[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O.[O-]S([O-])(=O)=O RUTXIHLAWFEWGM-UHFFFAOYSA-H 0.000 claims description 6
- 229910000360 iron(III) sulfate Inorganic materials 0.000 claims description 6
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 6
- 230000001681 protective effect Effects 0.000 claims description 6
- 150000003839 salts Chemical class 0.000 claims description 6
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 4
- 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
- 229910021578 Iron(III) chloride Inorganic materials 0.000 claims description 4
- 239000002253 acid Substances 0.000 claims description 4
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 4
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 4
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 4
- ZBCBWPMODOFKDW-UHFFFAOYSA-N diethanolamine Chemical compound OCCNCCO ZBCBWPMODOFKDW-UHFFFAOYSA-N 0.000 claims description 4
- RBTARNINKXHZNM-UHFFFAOYSA-K iron trichloride Chemical compound Cl[Fe](Cl)Cl RBTARNINKXHZNM-UHFFFAOYSA-K 0.000 claims description 4
- 238000010902 jet-milling Methods 0.000 claims description 4
- NUJOXMJBOLGQSY-UHFFFAOYSA-N manganese dioxide Chemical compound O=[Mn]=O NUJOXMJBOLGQSY-UHFFFAOYSA-N 0.000 claims description 4
- 235000010482 polyoxyethylene sorbitan monooleate Nutrition 0.000 claims description 4
- 229920000053 polysorbate 80 Polymers 0.000 claims description 4
- 239000002202 Polyethylene glycol Substances 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims description 3
- 229920001223 polyethylene glycol Polymers 0.000 claims description 3
- WBIQQQGBSDOWNP-UHFFFAOYSA-N 2-dodecylbenzenesulfonic acid Chemical compound CCCCCCCCCCCCC1=CC=CC=C1S(O)(=O)=O WBIQQQGBSDOWNP-UHFFFAOYSA-N 0.000 claims description 2
- 229920002472 Starch Polymers 0.000 claims description 2
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 2
- 229930006000 Sucrose Natural products 0.000 claims description 2
- 229910021542 Vanadium(IV) oxide Inorganic materials 0.000 claims description 2
- 229910052786 argon Inorganic materials 0.000 claims description 2
- 239000011668 ascorbic acid Substances 0.000 claims description 2
- 229960005070 ascorbic acid Drugs 0.000 claims description 2
- 235000010323 ascorbic acid Nutrition 0.000 claims description 2
- 239000001913 cellulose Substances 0.000 claims description 2
- 229920002678 cellulose Polymers 0.000 claims description 2
- 229940060296 dodecylbenzenesulfonic acid Drugs 0.000 claims description 2
- 229910052734 helium Inorganic materials 0.000 claims description 2
- 239000001307 helium Substances 0.000 claims description 2
- SWQJXJOGLNCZEY-UHFFFAOYSA-N helium atom Chemical compound [He] SWQJXJOGLNCZEY-UHFFFAOYSA-N 0.000 claims description 2
- 239000000395 magnesium oxide Substances 0.000 claims description 2
- CPLXHLVBOLITMK-UHFFFAOYSA-N magnesium oxide Inorganic materials [Mg]=O CPLXHLVBOLITMK-UHFFFAOYSA-N 0.000 claims description 2
- AXZKOIWUVFPNLO-UHFFFAOYSA-N magnesium;oxygen(2-) Chemical compound [O-2].[Mg+2] AXZKOIWUVFPNLO-UHFFFAOYSA-N 0.000 claims description 2
- 239000000203 mixture Substances 0.000 claims description 2
- TWNQGVIAIRXVLR-UHFFFAOYSA-N oxo(oxoalumanyloxy)alumane Chemical compound O=[Al]O[Al]=O TWNQGVIAIRXVLR-UHFFFAOYSA-N 0.000 claims description 2
- 239000008107 starch Substances 0.000 claims description 2
- 235000019698 starch Nutrition 0.000 claims description 2
- 239000005720 sucrose Substances 0.000 claims description 2
- GRUMUEUJTSXQOI-UHFFFAOYSA-N vanadium dioxide Chemical compound O=[V]=O GRUMUEUJTSXQOI-UHFFFAOYSA-N 0.000 claims description 2
- 239000011248 coating agent Substances 0.000 abstract description 4
- 238000000576 coating method Methods 0.000 abstract description 4
- 238000011065 in-situ storage Methods 0.000 abstract description 3
- 238000010923 batch production Methods 0.000 abstract description 2
- 230000001276 controlling effect Effects 0.000 description 21
- 238000005056 compaction Methods 0.000 description 12
- 230000000052 comparative effect Effects 0.000 description 12
- 238000012360 testing method Methods 0.000 description 10
- 230000015572 biosynthetic process Effects 0.000 description 9
- 238000009825 accumulation Methods 0.000 description 7
- 239000000178 monomer Substances 0.000 description 7
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 description 6
- 239000010405 anode material Substances 0.000 description 6
- 229910052742 iron Inorganic materials 0.000 description 5
- 239000002994 raw material Substances 0.000 description 5
- 238000010586 diagram Methods 0.000 description 4
- 238000009826 distribution Methods 0.000 description 4
- -1 iron ions Chemical class 0.000 description 4
- 239000010410 layer Substances 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 4
- 239000000126 substance Substances 0.000 description 4
- 238000011161 development Methods 0.000 description 3
- 239000012535 impurity Substances 0.000 description 3
- 230000001788 irregular Effects 0.000 description 3
- 239000012071 phase Substances 0.000 description 3
- 239000000843 powder Substances 0.000 description 3
- 239000007921 spray Substances 0.000 description 3
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 239000003792 electrolyte Substances 0.000 description 2
- 230000002572 peristaltic effect Effects 0.000 description 2
- 239000007774 positive electrode material Substances 0.000 description 2
- 230000001105 regulatory effect Effects 0.000 description 2
- 239000012798 spherical particle Substances 0.000 description 2
- 238000003756 stirring Methods 0.000 description 2
- 206010024769 Local reaction Diseases 0.000 description 1
- 239000002033 PVDF binder Substances 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 238000001354 calcination Methods 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 239000011247 coating layer Substances 0.000 description 1
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- 239000012530 fluid Substances 0.000 description 1
- 239000008187 granular material Substances 0.000 description 1
- 238000003837 high-temperature calcination Methods 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 0.000 description 1
- 238000009434 installation Methods 0.000 description 1
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N iron oxide Inorganic materials [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 description 1
- 238000007561 laser diffraction method Methods 0.000 description 1
- 238000001000 micrograph Methods 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 238000007709 nanocrystallization Methods 0.000 description 1
- NDLPOXTZKUMGOV-UHFFFAOYSA-N oxo(oxoferriooxy)iron hydrate Chemical compound O.O=[Fe]O[Fe]=O NDLPOXTZKUMGOV-UHFFFAOYSA-N 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 230000000704 physical effect Effects 0.000 description 1
- 229920002981 polyvinylidene fluoride Polymers 0.000 description 1
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- 238000007873 sieving Methods 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 238000010998 test method Methods 0.000 description 1
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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
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Abstract
The invention discloses ordered nano spherical lithium iron phosphate with high energy density and a preparation method thereof, wherein the ordered nano spherical lithium iron phosphate with high energy density is prepared from ordered nano large-particle iron phosphate, a small-particle lithium source, a carbon source and a doped metal oxide, the particle size ratio of the ordered nano large-particle iron phosphate to the small-particle lithium source is 2.0-2.8, and the molar ratio of the iron phosphate to lithium ions in the lithium source is 1:1.01 to 1.05. The iron phosphate is orderly stacked by controlling the structure of the iron phosphate and the particle size of raw and auxiliary material particles; and (3) uniformly mixing the slurry, performing spray drying to ensure that the surfaces of all the components are fully contacted, roasting, accumulating a small-particle lithium source on the surface of a large particle, participating in-situ reaction by a carbon source and uniformly coating the carbon source on the surface of the particle, and doping metal oxide to effectively prevent the particle from continuously growing so as to finally form the ordered nano spherical lithium iron phosphate. The preparation method disclosed by the invention is simple to operate, controllable in particle size and uniform in material mixing, and can be applied to industrial batch production, and the prepared lithium iron phosphate material has the characteristic of high energy density.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to ordered nano spherical lithium iron phosphate with high energy density and a preparation method thereof.
Background
The olivine-structured lithium iron phosphate serving as the lithium ion battery anode material has the advantages of high theoretical specific capacity, good charge-discharge and cycle performance, environmental friendliness, low price, wide raw material source and the like, and is paid much attention to by people. Nowadays, the development of lithium iron phosphate materials enters a high-speed development period, lithium iron phosphate batteries pursuing safer, more economical and better cycle performance become the mainstream of the market, and more companies begin to deeply develop advanced lithium iron phosphate material preparation technologies based on the considerable commercial application value of the lithium iron phosphate batteries. The energy density of the lithium iron phosphate battery is low under the influence of the characteristics of the anode material, and the lithium iron phosphate battery is a short plate influencing the endurance mileage. Therefore, it is necessary to develop a lithium iron phosphate positive electrode material with high energy density and better performance to solve the problems faced currently.
The lithium iron phosphate battery anode material has high requirements on components and phase purity, so that the metering accuracy and precision are ensured when the lithium iron phosphate battery anode material is weighed according to a raw material formula. In addition, the method has strict requirements on the uniformity of raw material mixing, otherwise, lithium iron phosphate is locally non-uniform to generate impurity phases, and the product performance is influenced. The adding quality and the particle size of different raw and auxiliary materials for preparing the lithium iron phosphate are different, so that impurities are easily generated due to nonuniform local reaction, and further, the phenomena of nonuniform carbon coating and doping occur when a carbon source and a doping substance are added, and the performance of the lithium iron phosphate material is finally influenced. Compared with powder with other shapes, the spherical granular lithium iron phosphate has the characteristics of lower interfacial energy, higher stacking density and specific energy, excellent fluidity, dispersibility, processing performance and the like, and is beneficial to the preparation of anode material slurry and the coating of electrodes, thereby improving the quality of battery pole pieces. When iron phosphate is used as a precursor to prepare lithium iron phosphate, iron phosphate particles are damaged in high-temperature calcination even if the iron phosphate particles have a spherical shape, which brings difficulty to the preparation of spherical lithium iron phosphate.
Generally, the overall performance of lithium iron phosphate cannot be improved by a single modification mode, and the cathode material with more excellent electrochemical performance can be prepared by combining the advantages of several modification strategies. Most reports on lithium iron phosphate with high energy density are that lithium iron phosphate with two particle sizes is simply mixed to improve the performance of the lithium iron phosphate material, but researches on the structure of the raw material and nanocrystallization are less. CN109301179A discloses a lithium iron phosphate anode material for lithium battery and its preparation method, mixing precipitator, ferric salt solution and additive in a three-neck flask, stirring and reacting at 65-90 deg.C, vacuum drying, ball milling, calcining to obtain dense ferric oxide powder, then preparing large and small granule lithium iron phosphate slurry, separately spray drying, mixing, high temperature sintering, powder sieving to obtain spherical lithium iron phosphate. However, this method only mixes the precursors of lithium iron phosphate with different particle sizes, and cannot fundamentally control the morphology structure of the material, and cannot realize higher compaction density of lithium iron phosphate. CN114314550A discloses a high energy density lithium iron phosphate and a preparation method thereof, wherein raw materials and auxiliary materials are homogenized, coarsely ground and finely ground to prepare a lithium iron phosphate slurry with a certain particle size, different from the above situation, a large-particle lithium iron phosphate precursor and a small-particle lithium iron phosphate precursor are prepared by controlling the particle size of ejected particles by adjusting the frequency of a centrifugal spray head, controlling the doping proportion of two different particle sizes by adjusting the flow rate of a centrifugal spray peristaltic pump and a two-fluid spray peristaltic pump, and finally sintering in a protective atmosphere to prepare the lithium iron phosphate. However, the preparation method is complex, the prepared spherical lithium iron phosphate has non-uniform particle size and irregular spherical structure, and the compaction density and energy density of the lithium iron phosphate material are still difficult to improve.
Disclosure of Invention
The invention discloses ordered nano spherical lithium iron phosphate with high energy density and a preparation method thereof, aiming at the problem that the compacted density and the energy density of a lithium iron phosphate material in the prior art are difficult to comprehensively improve.
The invention is realized by the following technical scheme:
the ordered nanometer spherical lithium iron phosphate with high energy density comprises ordered nanometer large-particle iron phosphate and a small-particle lithium source, wherein the particle size ratio of the ordered nanometer large-particle iron phosphate to the small-particle lithium source is 2.0-2.8, and the molar ratio of the iron phosphate to lithium ions in the lithium source is 1:1.01 to 1.05.
Further, the median particle diameter Dv50 of the ordered nano large-particle iron phosphate is 0.50-0.98 μm; the median particle diameter Dv50 of the small-particle lithium source is 0.25 to 0.35 μm.
The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps:
(1) Preparing ordered nano large-particle iron phosphate slurry: under the environment with strong acid as a medium, controlling the molar ratio of the trivalent ferric salt to the phosphorus source to be 1:1.1 to 1.5, slowly adding a trivalent ferric salt, a phosphorus source and an additive, reacting in a liquid phase at 70-80 ℃ for 4-6 hours, filtering, washing, and vacuum-drying at 90-100 ℃ for 1-2 hours to obtain ordered nano iron phosphate, and mixing the ordered nano iron phosphate with water in proportion, homogenizing and grinding to obtain an ordered nano large-particle iron phosphate slurry;
(2) Preparation of small-particle lithium source slurry: mixing a lithium source, a carbon source, a doping substance and water in proportion, homogenizing and grinding to prepare small-particle lithium source slurry;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the ferric phosphate to lithium ions in the lithium source to be 1:1.01 to 1.05, fully mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) with the small-particle lithium source slurry prepared in the step (2), and performing spray drying to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) performing high-temperature sintering and jet milling on the lithium iron phosphate precursor in the step (3) to obtain the ordered nano spherical lithium iron phosphate with high energy density.
Further, the strong acid in the step (1) is nitric acid and/or sulfuric acid with the concentration of 80-90%; the ferric salt is more than one of ferric nitrate, ferric sulfate and ferric chloride with the concentration of 15-30 wt%; the phosphorus source is more than one of phosphoric acid with the concentration of 7-37wt%, ammonium dihydrogen phosphate and diammonium hydrogen phosphate; the additive is one or more of dodecyl benzene sulfonic acid, sodium dodecyl sulfate, polyethylene glycol, diethanolamine and Tween 80 with concentration of 4-6 mg/mL.
Further, the mass ratio of the ferric phosphate to the water in the ordered nano large-particle ferric phosphate slurry in the step (1) is 36-60:100, respectively; the mass ratio of the lithium source, the carbon source, the doping material and the water in the small-particle lithium source slurry in the step (2) is 6-29:2-8:0.2-0.8:100.
further, the lithium source in the step (2) is more than one of lithium carbonate, lithium chloride, lithium nitrate and lithium hydroxide; the carbon source is more than one of soluble starch, cellulose, sucrose, glucose and ascorbic acid; the doping material is more than one of magnesium oxide, aluminum oxide, manganese dioxide, titanium dioxide and vanadium dioxide.
Further, the spray drying conditions in the step (3) are that the centrifugal frequency is 500-600HZ, the feeding flow is 40-60rpm, and the air temperature is 150-250 ℃.
Further, the high-temperature sintering process in the step (4) comprises the following steps: setting the protective atmosphere as nitrogen, argon or helium, heating to 300-350 ℃ at the heating rate of 4 ℃/min, preserving heat for 1-2 hours, heating to 600-700 ℃ at the heating rate of 3 ℃/min, and preserving heat for 10-12 hours.
Further, the jet milling process in the step (4) has the air pressure of 0.6-0.8MPa and the frequency of 300-350HZ.
Ordered nano spherical lithium iron phosphate with high energy density is firstly based on morphology control, the prepared ordered nano iron phosphate is in a regular cake-shaped structure, and the ordered nano iron phosphate is orderly stacked by controlling the particle size of raw and auxiliary material particles; secondly, after the slurry is uniformly mixed, spray drying is carried out, so that the surfaces of all the components are fully contacted; then sintering at high temperature to obtain small-particle lithium sourceThe carbon source is accumulated on the surface of the large particles, the carbon source participates in-situ reaction and is uniformly coated on the surface of the particles, and the doped metal oxide can effectively prevent the particles from continuously growing to finally form the ordered nano spherical particles. The synthesis process has the following characteristics: regular cake-shaped structure ferric phosphate, raw and auxiliary material particle size control, ordered nanometer spherical lithium iron phosphate. According to the invention, the growth of iron phosphate crystals is controlled by the additive, so that the morphological development of the iron phosphate crystals is controlled, the sizes of the formed iron phosphate particles are uniform and are arranged in a certain sequence, and the consistency of the particle structures of the lithium iron phosphate particles is ensured; the particle size of the raw and auxiliary materials is strictly controlled, large-particle iron phosphate slurry is ground and the particle size is regulated, and small-particle lithium source slurry containing a lithium source, a carbon source and a doping substance is ground and the particle size is regulated, so that large particles and small particles are orderly stacked. After mixing uniformly, spray drying is carried out to ensure that the surfaces of all the components are fully contacted. The carbon source is added to enable the surface of the particles to be covered by the carbon layer, so that direct contact among the particles can be hindered, the particles can be effectively inhibited from becoming large, meanwhile, the electrical contact among materials can be improved, and the electrical conductivity of the materials can be improved. The metal oxide can be used as a doping substance to prevent the continuous growth of particles, control the particle size and shorten the transmission distance of lithium ions. Ordered nano spherical lithium iron phosphate with ordered arrangement and uniform particle size is formed by high-temperature sintering and jet milling, so that the compaction density of the material is improved, and the compaction density reaches 2.55-2.70g/cm when the material is detected by using a compaction density instrument 3 。
The method finally synthesizes the ordered nano spherical lithium iron phosphate with high energy density, and has high gram capacity and monomer energy density besides high compaction density. Through assembling the button cell, performing charge-discharge test at 0.1C multiplying power, the first discharge specific capacity reaches 156.5 to 158.6mAh/g; the mass energy density of the produced columnar lithium iron phosphate battery is tested to reach 153 to 165Wh/kg, and the columnar lithium iron phosphate battery shows good electrochemical performance.
Advantageous effects
The ordered nano iron phosphate prepared by the method is of a regular cake-shaped structure, the particles of raw and auxiliary materials are orderly stacked by controlling the particle size, spray drying is carried out after slurry is uniformly mixed, the surfaces of all components are fully contacted, then small-particle lithium sources are stacked on the surface of large particles by roasting, the carbon sources participate in-situ reaction and form uniform coating layers on the surfaces of the particles, and the particles can be effectively prevented from continuously growing by doping metal oxides, so that the ordered nano spherical particles are finally formed. The preparation process and the operation are simple, the particle size of the raw and auxiliary materials is controllable, the mixture of the precursor and the finished product is uniform, and the preparation method can be applied to industrial batch production. In the practical production process, when the reason for causing the low physical property and electrochemical property of the lithium iron phosphate material is analyzed, the comprehensive performance of the lithium iron phosphate material can be improved by considering the structures of a phosphorus source or an iron source and a lithium source, the particle sizes of raw and auxiliary materials and the like.
Drawings
FIG. 1 is a process flow diagram of the preparation method of the high energy density ordered nano spherical lithium iron phosphate of the present invention;
FIG. 2 is a schematic diagram of a lithium iron phosphate stacking reaction according to the present invention;
fig. 3 is an SEM electron microscope image of the ordered nano spherical lithium iron phosphate with high energy density according to embodiment 1 of the present invention.
Detailed Description
The following description is given with reference to specific examples, which are only representative examples of the present invention, and not all examples, and various changes and modifications can be made based on the present invention, and these changes and modifications are within the protection scope of the present invention. Therefore, all other embodiments obtained by persons skilled in the art based on the embodiments of the present invention without any inventive work belong to the protection scope of the present invention.
Example 1
(1) Preparing the ordered nano large-particle iron phosphate slurry: under the environment with 90% nitric acid as a medium, controlling the molar ratio of ferric nitrate to phosphoric acid to be 1:1.5, slowly adding ferric nitrate, phosphoric acid and sodium dodecyl sulfate to ensure that the concentration of the ferric nitrate is 30wt%, the concentration of the phosphoric acid is 18wt% and the concentration of the sodium dodecyl sulfate is 6mg/mL, carrying out liquid phase reaction at 75 ℃ for 5 hours, filtering, washing, and carrying out vacuum drying at 95 ℃ for 1.5 hours to obtain ordered nano ferric phosphate, mixing the ordered nano ferric phosphate with water according to the weight ratio of 60:100, and preparing ordered nano large-particle iron phosphate slurry with the median particle size Dv50 of 0.90-0.98 mu m, wherein the large-particle iron phosphate has a special cake-shaped structure, and the ordered structure is reserved in the stacking reaction process;
"median particle diameter Dv50" refers to the particle diameter corresponding to 50% of the cumulative particle size distribution of the particles in the particle size distribution curve, and the physical meaning is that the particles having a particle diameter less than (or greater than) 50% of the total particle size distribution. The used test instrument is a laser particle size analyzer, and the test process refers to a GB/T19077-2016 particle size distribution laser diffraction method;
(2) Preparation of small-particle lithium source slurry: mixing lithium carbonate, glucose, titanium dioxide and water according to the weight ratio of 15:8:0.5:100, homogenizing and grinding to prepare lithium source small particle slurry with the median particle diameter Dv50 of 0.27-0.33 mu m, wherein a small particle phosphorus source is accumulated on the surface of a large particle to participate in the formation of a spherical structure in the accumulation reaction process;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the lithium ions in the iron phosphate and the lithium carbonate to be 1:1.05, mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) and the small-particle lithium source slurry prepared in the step (2) in equal volume, and performing spray drying at the centrifugal frequency of 500HZ, the feeding flow rate of 45rpm and the wind temperature of 160 ℃ to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature in a nitrogen protective atmosphere, heating to 300 ℃ at a heating rate of 4 ℃/min, preserving heat for 1.5 hours, heating to 700 ℃ at a heating rate of 3 ℃/min, preserving heat for 10 hours, and then carrying out air flow crushing at a 300HZ frequency under the air pressure of 0.6MPa to obtain the high-energy-density ordered nano spherical lithium iron phosphate.
In this example, the preparation of the material was carried out according to the process flow diagram of FIG. 1; in the stacking reaction schematic diagram shown in fig. 2, gray circles and black circles represent ordered nano large-particle iron phosphate and small-particle lithium sources, respectively, and the large particles and the small particles are characterized by being arranged layer by layer at intervals; in the SEM electron micrograph of fig. 3, the particle morphology is regular and spherical, it can be seen that the control of the nano-ordered iron phosphate structure and the particle size of the raw and auxiliary material particles plays a leading role in controlling the morphology of the lithium iron phosphate, and in addition, the carbon source, the doping material, and the process parameters have an important influence on the formation of the final lithium iron phosphate.
Example 2
(1) Preparing ordered nano large-particle iron phosphate slurry: under the environment with 80% nitric acid as a medium, controlling the molar ratio of iron ions to phosphate ions to be 1:1.1, slowly adding ferric nitrate, phosphoric acid and sodium dodecyl sulfate to ensure that the concentration of the ferric nitrate is 20wt%, the concentration of the phosphoric acid is 9wt% and the concentration of the sodium dodecyl sulfate is 5mg/mL, carrying out liquid phase reaction at 70 ℃ for 6 hours, filtering, washing, and carrying out vacuum drying at 90 ℃ for 2 hours to obtain ordered nano ferric phosphate, mixing the ordered nano ferric phosphate with water according to a ratio of 36:100, and preparing ordered nano large-particle iron phosphate slurry with the median particle size Dv50 of 0.50-0.60 mu m, wherein the large-particle iron phosphate has a special cake-shaped structure, and the ordered structure is reserved in the stacking reaction process;
(2) Preparation of small-particle lithium source slurry: mixing lithium carbonate, glucose, titanium dioxide and water according to the weight ratio of 9:2:0.2:100, homogenizing and grinding to prepare lithium source small particle slurry with the median particle diameter Dv50 of 0.25-0.35 mu m, wherein a small particle phosphorus source is accumulated on the surface of a large particle to participate in the formation of a spherical structure in the accumulation reaction process;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the lithium ions in the iron phosphate and the lithium carbonate to be 1:1.01, mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) and the small-particle lithium source slurry prepared in the step (2) in equal volume, and performing spray drying at the centrifugal frequency of 550HZ, the feeding flow of 55rpm and the wind temperature of 200 ℃ to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature in a nitrogen protective atmosphere, heating to 320 ℃ at a heating rate of 4 ℃/min, preserving heat for 1.5 hours, heating to 650 ℃ at a heating rate of 3 ℃/min, preserving heat for 11 hours, and then carrying out air flow crushing at a pressure of 0.7MPa and a frequency of 320HZ to obtain the high-energy-density ordered nano spherical lithium iron phosphate.
Example 3
(1) Preparing ordered nano large-particle iron phosphate slurry: under the environment with 85% nitric acid as a medium, controlling the molar ratio of iron ions to phosphate ions to be 1: and 1.3, slowly adding ferric sulfate, ammonium dihydrogen phosphate and decapolyethylene glycol to ensure that the concentration of the ferric sulfate is 15wt%, the concentration of the ammonium dihydrogen phosphate is 11wt% and the concentration of the polyethylene glycol is 4mg/mL, carrying out liquid-phase reaction at 80 ℃ for 4 hours, filtering, washing, carrying out vacuum drying at 100 ℃ for 1 hour to obtain ordered nano ferric phosphate, and mixing the ordered nano ferric phosphate with water according to the weight ratio of 60:100, and preparing ordered nano large-particle iron phosphate slurry with the median particle size Dv50 of 0.90-0.98 mu m, wherein the large-particle iron phosphate has a special cake-shaped structure, and the ordered structure is reserved in the stacking reaction process;
(2) Preparation of small-particle lithium source slurry: mixing lithium chloride, glucose, titanium dioxide and water according to the weight ratio of 18:2:0.2:100, and homogenizing and grinding to prepare lithium source small particle slurry with a median particle diameter Dv50 of 0.25-0.30 mu m, wherein a small particle phosphorus source is accumulated on the surface of a large particle to participate in the formation of a spherical structure in the accumulation reaction process;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the ferric phosphate to the lithium chloride to be 1:1.05, mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) and the small-particle lithium source slurry prepared in the step (2) in equal volume, and performing spray drying at 600HZ centrifugal frequency, 60rpm feeding flow and air temperature of 250 ℃ to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature in a nitrogen protective atmosphere, heating to 350 ℃ at a heating rate of 4 ℃/min, preserving heat for 1.5 hours, heating to 650 ℃ at a heating rate of 3 ℃/min, preserving heat for 11 hours, and then carrying out air flow crushing at a pressure of 0.8MPa and a frequency of 350HZ to obtain the high-energy-density ordered nano spherical lithium iron phosphate.
Example 4
(1) Preparing ordered nano large-particle iron phosphate slurry: under the environment with 90% sulfuric acid as a medium, controlling the molar ratio of iron ions to phosphate ions to be 1:1.5, slowly adding ferric sulfate, ammonium dihydrogen phosphate and diethanolamine to ensure that the concentration of the ferric sulfate is 30wt%, the concentration of the ammonium dihydrogen phosphate is 26wt% and the concentration of the diethanolamine is 6mg/mL, carrying out liquid-phase reaction at 75 ℃ for 5 hours, filtering, washing, and carrying out vacuum drying at 95 ℃ for 1.5 hours to obtain ordered nano iron phosphate, mixing the ordered nano iron phosphate with water according to the weight ratio of 48:100, and preparing ordered nano large-particle iron phosphate slurry with the median particle diameter Dv50 of 0.70-0.80 mu m, wherein the large-particle iron phosphate has a special cake-shaped structure, and the ordered structure is reserved in the stacking reaction process;
(2) Preparation of small-particle lithium source slurry: mixing lithium nitrate, glucose, titanium dioxide and water according to a ratio of 23:8:0.5:100, homogenizing and grinding to prepare lithium source small particle slurry with the median particle diameter Dv50 of 0.27-0.33 mu m, wherein a small particle phosphorus source is accumulated on the surface of a large particle to participate in the formation of a spherical structure in the accumulation reaction process;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the ferric phosphate to the lithium nitrate to be 1:1.03, mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) and the small-particle lithium source slurry prepared in the step (2) in equal volume, and performing spray drying at the centrifugal frequency of 500HZ, the feeding flow rate of 45rpm and the wind temperature of 160 ℃ to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature under the nitrogen protection atmosphere, heating to 300 ℃ at the heating rate of 4 ℃/min, preserving the heat for 1.5 hours, heating to 700 ℃ at the heating rate of 3 ℃/min, preserving the heat for 10 hours, and then carrying out airflow crushing at the air pressure of 0.6MPa and the frequency of 300HZ to obtain the high-energy-density ordered nano spherical lithium iron phosphate.
Example 5
(1) Preparing the ordered nano large-particle iron phosphate slurry: under the environment with 90% sulfuric acid as a medium, controlling the molar ratio of iron ions to phosphate ions to be 1:1.3, slowly adding ferric chloride, diammonium hydrogen phosphate and tween 80 to ensure that the concentration of the ferric chloride is 30wt%, the concentration of the diammonium hydrogen phosphate is 32wt% and the concentration of the tween 80 is 6mg/mL, carrying out liquid phase reaction at 75 ℃ for 5 hours, filtering, washing, and carrying out vacuum drying at 95 ℃ for 1.5 hours to obtain ordered nano ferric phosphate, mixing the ordered nano ferric phosphate with water according to the weight ratio of 48:100, and preparing ordered nano large-particle iron phosphate slurry with the median particle size Dv50 of 0.70-0.80 mu m, wherein the large-particle iron phosphate has a special cake-shaped structure, and the ordered structure is reserved in the stacking reaction process;
(2) Preparation of small-particle lithium source slurry: mixing lithium hydroxide, glucose, titanium dioxide and water according to the weight ratio of 8:8:0.5:100, homogenizing and grinding to prepare lithium source small particle slurry with the median particle diameter Dv50 of 0.27-0.33 mu m, wherein a small particle phosphorus source is accumulated on the surface of a large particle to participate in the formation of a spherical structure in the accumulation reaction process;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the ferric phosphate to the lithium hydroxide to be 1:1.01, mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) and the small-particle lithium source slurry prepared in the step (2) in equal volume, and performing spray drying at the centrifugal frequency of 500HZ, the feeding flow rate of 45rpm and the wind temperature of 160 ℃ to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature under the nitrogen protection atmosphere, heating to 300 ℃ at the heating rate of 4 ℃/min, preserving the heat for 1.5 hours, heating to 700 ℃ at the heating rate of 3 ℃/min, preserving the heat for 10 hours, and then carrying out airflow crushing at the air pressure of 0.6MPa and the frequency of 300HZ to obtain the high-energy-density ordered nano spherical lithium iron phosphate.
Comparative example 1
(1) Preparing nano large-particle iron phosphate slurry: under the environment with 90% nitric acid as a medium, controlling the molar ratio of ferric nitrate to phosphoric acid to be 1:1.5, slowly adding ferric nitrate and phosphoric acid to ensure that the ferric nitrate concentration is 30wt% and the phosphoric acid concentration is 18wt%, carrying out liquid phase reaction at 75 ℃ for 5 hours, filtering, washing, and carrying out vacuum drying at 95 ℃ for 1.5 hours to obtain nano ferric phosphate, and mixing the nano ferric phosphate with water according to a ratio of 60:100, and preparing nano large-particle iron phosphate slurry with the median particle diameter Dv50 of 0.90-0.98 mu m, wherein the large-particle iron phosphate exists in an irregular structure, and the disordered structure is reserved in the stacking reaction process;
(2) Preparation of small-particle lithium source slurry: mixing lithium carbonate, glucose, titanium dioxide and water according to the weight ratio of 15:8:0.5:100, and homogenizing and grinding to prepare lithium source small particle slurry with a median particle size Dv50 of 0.27-0.33 mu m, wherein a small particle phosphorus source is accumulated on the surface of a large particle in the accumulation reaction process to participate in the formation of a lithium iron phosphate structure;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of lithium ions in the iron phosphate and the lithium carbonate to be 1:1.05, isovolumetrically and fully mixing the nano large-particle iron phosphate slurry prepared in the step (1) and the small-particle lithium source slurry prepared in the step (2), and carrying out spray drying at the centrifugal frequency of 500HZ, the feeding flow rate of 45rpm and the wind temperature of 160 ℃ to obtain a lithium iron phosphate precursor;
(4) Preparing lithium iron phosphate: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature under the nitrogen protection atmosphere, heating to 300 ℃ at the heating rate of 4 ℃/min, preserving heat for 1.5 hours, heating to 700 ℃ at the heating rate of 3 ℃/min, preserving heat for 10 hours, and then carrying out air flow crushing at the air pressure of 0.6MPa and the frequency of 300HZ to obtain the lithium iron phosphate.
Comparative example 2
(1) Preparing the uncontrollable particle size ordered nano iron phosphate slurry: under the environment with 90% nitric acid as a medium, controlling the molar ratio of ferric nitrate to phosphoric acid to be 1:1.5, slowly adding ferric nitrate, phosphoric acid and sodium dodecyl sulfate to ensure that the concentration of the ferric nitrate is 30wt%, the concentration of the phosphoric acid is 18wt% and the concentration of the sodium dodecyl sulfate is 6mg/mL, carrying out liquid phase reaction for 5 hours at the temperature of 75 ℃, filtering, washing, and carrying out vacuum drying for 1.5 hours at the temperature of 95 ℃ to obtain ordered nano ferric phosphate, mixing the ordered nano ferric phosphate with water according to the weight ratio of 60:100, and preparing an ordered nano iron phosphate slurry with uncontrollable median particle size Dv50 without grinding, wherein the iron phosphate exists in a cake-shaped structure with larger particles and is not beneficial to the formation of single products and uniform particles in the stacking reaction process;
(2) Preparing uncontrollable particle size lithium source slurry: mixing lithium carbonate, glucose, titanium dioxide and water according to the weight ratio of 15:8:0.5:100, and preparing lithium source slurry with uncontrollable median particle size without grinding, wherein a phosphorus source is accumulated on the surface of a larger particle in the accumulation reaction process, so that lithium iron phosphate with heterogeneous impurity phases or morphologies is easily formed.
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the ferric phosphate to lithium ions in the lithium source to be 1:1.05, mixing the uncontrollable particle size ordered nano iron phosphate slurry prepared in the step (1) and the uncontrollable particle size lithium source slurry prepared in the step (2) in equal volume, fully mixing, and carrying out spray drying at the centrifugal frequency of 500HZ, the feeding flow rate of 45rpm and the wind temperature of 160 ℃ to obtain a lithium iron phosphate precursor;
(4) Preparing lithium iron phosphate: and (4) sintering the ferric lithium precursor in the step (3) at a high temperature under the nitrogen protection atmosphere, heating to 300 ℃ at the heating rate of 4 ℃/min, preserving heat for 1.5 hours, heating to 700 ℃ at the heating rate of 3 ℃/min, preserving heat for 10 hours, and then carrying out air flow crushing at the air pressure of 0.6MPa and the frequency of 300HZ to obtain the lithium iron phosphate.
Electrochemical performance test
The test method comprises the following steps:
(1) Compacting density: detecting the prepared lithium iron phosphate by using a compaction density instrument, and calculating to obtain a compaction density value;
(2) Gram volume: preparing the prepared lithium iron phosphate, sp, KS-15, PVDF and NMP in proportion, preparing a positive plate by vacuum stirring, ball milling and mixing, coating, drying, rolling and cutting, completing the assembly of the button cell in a glove box according to the installation or dropwise adding sequence of a negative shell, a gasket, electrolyte, a gasket (with the positive plate), electrolyte, a diaphragm, a lithium plate, a positive shell and a seal, setting the test voltage range to be 2.0 to 3.8V at the temperature of 25 ℃, performing charge-discharge test at the multiplying power of 0.1C, and calculating to obtain a gram volume value;
(3) Energy density of monomer: and manufacturing a full battery, carrying out charge and discharge tests on the cylindrical battery by using a battery tester, and calculating to obtain a monomer energy density value.
The compacted density, the gram capacity and the monomer energy density of the lithium iron phosphate prepared by the comparative example and the example were measured, and the results are shown in table 1.
TABLE 1 test results of lithium iron phosphate Performance of comparative examples 1, 2 and examples 1 to 5
As can be seen from the data in Table 1, the compaction density of the ordered nano spherical lithium iron phosphate prepared by the method of the invention reaches 2.55 to 2.70g/cm 3 The specific discharge capacity at 0.1C for the first time reaches 156.5 to 158.6mAh/g, the mass energy density reaches 153 to 165Wh/kg, and the high compaction density, gram capacity and monomer energy density characteristics are shown.
Comparing and analyzing the test data of the lithium iron phosphate prepared in the comparative example 1 and the test data of the lithium iron phosphate prepared in the example 1, the compacted density of the lithium iron phosphate prepared in the example 1 is higher than that of the comparative example 1, and the gram capacity and the monomer energy density are higher than those of the comparative example 1, because the ordered large particles and the small particles are stacked in a layer-to-layer alternate arrangement mode, the prepared lithium iron phosphate is in an ordered nano spherical structure, and the compacted density and the electrochemical performance of the positive electrode material of the lithium iron phosphate battery are improved. The compacted density of the lithium iron phosphate prepared in comparative example 1 was 2.25 g/cm 3 The initial discharge specific capacity of 0.1C is 140mAh/g, and the mass energy density is 144Wh/kg, so that the prepared lithium iron phosphate has a disordered structure due to the fact that gaps are generated when particles with irregular structures are stacked, the compaction density is reduced, and the electrochemical performance is reduced.
Comparing and analyzing the test data of the lithium iron phosphate prepared in the comparative example 2 and the lithium iron phosphate prepared in the example 1, the compacted density of the lithium iron phosphate prepared in the example 1 is lower than that of the comparative example 2, the gram capacity and the monomer energy density are higher than those of the comparative example 2, and the compacted density of the lithium iron phosphate prepared in the comparative example 2 is 2.72 g/cm 3 The first discharge specific capacity of 0.1C is 132mAh/g, and the mass energy density is 140Wh/kg, and it can be seen that, in the stacking reaction process, since the non-ground iron phosphate exists in a cake-like structure of larger particles, the non-ground lithium source is stacked on the surface of the larger particles, the prepared lithium iron phosphate has poor unicity and uniformity, the particles are larger, so that the compaction density is increased, and the electrochemical performance is poor.
Claims (9)
1. The ordered nanometer spherical lithium iron phosphate with high energy density is characterized by comprising ordered nanometer large-particle iron phosphate, a small-particle lithium source, a carbon source and a doped metal oxide, wherein the particle size ratio of the ordered nanometer large-particle iron phosphate to the small-particle lithium source is 2.0-2.8, and the molar ratio of the iron phosphate to lithium ions in the lithium source is 1:1.01 to 1.05.
2. The high energy density ordered nano-spherical lithium iron phosphate according to claim 1, wherein the ordered nano-macroparticulate iron phosphate has a median particle diameter Dv50 of 0.50-0.98 μm; the median particle diameter Dv50 of the small-particle lithium source is 0.25 to 0.35 μm.
3. The method for preparing the ordered nano spherical lithium iron phosphate with high energy density according to claim 1 or 2, which is characterized by comprising the following steps:
(1) Preparing ordered nano large-particle iron phosphate slurry: under the environment with strong acid as a medium, controlling the molar ratio of the trivalent ferric salt to the phosphorus source to be 1: slowly adding trivalent ferric salt, a phosphorus source and an additive into the mixture for 1.1 to 1.5, carrying out liquid phase reaction at the temperature of 70-80 ℃ for 4-6 hours, filtering, washing, and carrying out vacuum drying at the temperature of 90-100 ℃ for 1-2 hours to obtain ordered nano iron phosphate, mixing the ordered nano iron phosphate with water in proportion, homogenizing and grinding to obtain an ordered nano large-particle iron phosphate slurry;
(2) Preparation of small-particle lithium source slurry: mixing a lithium source, a carbon source, a doping material and water in proportion, homogenizing and grinding to prepare small-particle lithium source slurry;
(3) Preparing a lithium iron phosphate precursor: controlling the molar ratio of the ferric phosphate to lithium ions in the lithium source to be 1:1.01 to 1.05, fully mixing the ordered nano large-particle iron phosphate slurry prepared in the step (1) with the small-particle lithium source slurry prepared in the step (2), and performing spray drying to obtain a lithium iron phosphate precursor;
(4) The preparation method of the ordered nano spherical lithium iron phosphate with high energy density comprises the following steps: and (4) performing high-temperature sintering and air flow crushing on the lithium iron phosphate precursor in the step (3) to obtain the ordered nano spherical lithium iron phosphate with high energy density.
4. The method according to claim 3, wherein the strong acid in the step (1) is nitric acid and/or sulfuric acid having a concentration of 80 to 90%; the ferric salt is more than one of ferric nitrate, ferric sulfate and ferric chloride with the concentration of 15-30 wt%; the phosphorus source is more than one of phosphoric acid with the concentration of 7-37wt%, ammonium dihydrogen phosphate and diammonium hydrogen phosphate; the additive is one or more of dodecyl benzene sulfonic acid, sodium dodecyl sulfate, polyethylene glycol, diethanolamine and Tween 80 with concentration of 4-6 mg/mL.
5. The preparation method according to claim 3, wherein the mass ratio of the ferric phosphate to the water in the ordered nano large-particle ferric phosphate slurry in the step (1) is 36-60:100, respectively; the mass ratio of the lithium source, the carbon source, the doping material and the water in the small-particle lithium source slurry in the step (2) is 6-29:2-8:0.2-0.8:100.
6. the method according to claim 3, wherein the lithium source in step (2) is one or more of lithium carbonate, lithium chloride, lithium nitrate, and lithium hydroxide; the carbon source is more than one of soluble starch, cellulose, sucrose, glucose and ascorbic acid; the doping material is more than one of magnesium oxide, aluminum oxide, manganese dioxide, titanium dioxide and vanadium dioxide.
7. The production process according to claim 3, wherein the spray drying conditions in the step (3) are a centrifugal frequency of 500 to 600Hz, a feed rate of 40 to 60rpm, and a wind temperature of 150 to 250 ℃.
8. The method according to claim 3, wherein the high-temperature sintering process in the step (4) is: setting the protective atmosphere as nitrogen, argon or helium, heating to 300-350 ℃ at the heating rate of 4 ℃/min, preserving heat for 1-2 hours, heating to 600-700 ℃ at the heating rate of 3 ℃/min, and preserving heat for 10-12 hours.
9. The method according to claim 3, wherein the jet milling in the step (4) is carried out under a pressure of 0.6 to 0.8MPa and at a frequency of 300 to 350HZ.
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