CN116404155A - Modified lithium iron phosphate positive electrode material, preparation method and application thereof - Google Patents
Modified lithium iron phosphate positive electrode material, preparation method and application thereof Download PDFInfo
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- CN116404155A CN116404155A CN202310596439.4A CN202310596439A CN116404155A CN 116404155 A CN116404155 A CN 116404155A CN 202310596439 A CN202310596439 A CN 202310596439A CN 116404155 A CN116404155 A CN 116404155A
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical class [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 139
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 48
- 238000002360 preparation method Methods 0.000 title abstract description 11
- 239000000463 material Substances 0.000 claims abstract description 114
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 33
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 26
- RGPUVZXXZFNFBF-UHFFFAOYSA-K diphosphonooxyalumanyl dihydrogen phosphate Chemical compound [Al+3].OP(O)([O-])=O.OP(O)([O-])=O.OP(O)([O-])=O RGPUVZXXZFNFBF-UHFFFAOYSA-K 0.000 claims abstract description 25
- 229910052746 lanthanum Inorganic materials 0.000 claims abstract description 25
- FZLIPJUXYLNCLC-UHFFFAOYSA-N lanthanum atom Chemical compound [La] FZLIPJUXYLNCLC-UHFFFAOYSA-N 0.000 claims abstract description 23
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 22
- 239000011737 fluorine Substances 0.000 claims abstract description 22
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 20
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 20
- 239000010405 anode material Substances 0.000 claims abstract description 18
- 239000000126 substance Substances 0.000 claims abstract description 14
- 238000005245 sintering Methods 0.000 claims description 45
- 238000000227 grinding Methods 0.000 claims description 38
- 239000011261 inert gas Substances 0.000 claims description 26
- 239000005955 Ferric phosphate Substances 0.000 claims description 21
- 229940032958 ferric phosphate Drugs 0.000 claims description 21
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical group [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 21
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 21
- 238000002156 mixing Methods 0.000 claims description 21
- 238000001694 spray drying Methods 0.000 claims description 21
- 238000000034 method Methods 0.000 claims description 17
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 16
- ILRRQNADMUWWFW-UHFFFAOYSA-K aluminium phosphate Chemical compound O1[Al]2OP1(=O)O2 ILRRQNADMUWWFW-UHFFFAOYSA-K 0.000 claims description 16
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 15
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 15
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 15
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 15
- PQXKHYXIUOZZFA-UHFFFAOYSA-M lithium fluoride Chemical compound [Li+].[F-] PQXKHYXIUOZZFA-UHFFFAOYSA-M 0.000 claims description 14
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 13
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 12
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims description 12
- 229910052799 carbon Inorganic materials 0.000 claims description 12
- 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
- 239000002019 doping agent Substances 0.000 claims description 12
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims description 12
- NBIIXXVUZAFLBC-UHFFFAOYSA-L Phosphate ion(2-) Chemical compound OP([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-L 0.000 claims description 11
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims description 11
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 229910052698 phosphorus Inorganic materials 0.000 claims description 11
- 239000011574 phosphorus Substances 0.000 claims description 11
- 239000002243 precursor Substances 0.000 claims description 11
- 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 10
- 239000008103 glucose Substances 0.000 claims description 10
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 8
- 229910052757 nitrogen Inorganic materials 0.000 claims description 8
- NROKBHXJSPEDAR-UHFFFAOYSA-M potassium fluoride Chemical compound [F-].[K+] NROKBHXJSPEDAR-UHFFFAOYSA-M 0.000 claims description 8
- 238000000498 ball milling Methods 0.000 claims description 7
- 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 7
- 229910017569 La2(CO3)3 Inorganic materials 0.000 claims description 6
- 229910052786 argon Inorganic materials 0.000 claims description 6
- NZPIUJUFIFZSPW-UHFFFAOYSA-H lanthanum carbonate Chemical compound [La+3].[La+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O NZPIUJUFIFZSPW-UHFFFAOYSA-H 0.000 claims description 6
- 229960001633 lanthanum carbonate Drugs 0.000 claims description 6
- MRELNEQAGSRDBK-UHFFFAOYSA-N lanthanum(3+);oxygen(2-) Chemical compound [O-2].[O-2].[O-2].[La+3].[La+3] MRELNEQAGSRDBK-UHFFFAOYSA-N 0.000 claims description 6
- 235000013024 sodium fluoride Nutrition 0.000 claims description 6
- 239000011775 sodium fluoride Substances 0.000 claims description 6
- 230000000630 rising effect Effects 0.000 claims description 5
- 229920000858 Cyclodextrin Polymers 0.000 claims description 4
- 229920002472 Starch Polymers 0.000 claims description 4
- 229930006000 Sucrose Natural products 0.000 claims description 4
- JLRJWBUSTKIQQH-UHFFFAOYSA-K lanthanum(3+);triacetate Chemical compound [La+3].CC([O-])=O.CC([O-])=O.CC([O-])=O JLRJWBUSTKIQQH-UHFFFAOYSA-K 0.000 claims description 4
- XIXADJRWDQXREU-UHFFFAOYSA-M lithium acetate Chemical compound [Li+].CC([O-])=O XIXADJRWDQXREU-UHFFFAOYSA-M 0.000 claims description 4
- 235000003270 potassium fluoride Nutrition 0.000 claims description 4
- 239000011698 potassium fluoride Substances 0.000 claims description 4
- HFHDHCJBZVLPGP-UHFFFAOYSA-N schardinger α-dextrin Chemical compound O1C(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC(C(O)C2O)C(CO)OC2OC(C(C2O)O)C(CO)OC2OC2C(O)C(O)C1OC2CO HFHDHCJBZVLPGP-UHFFFAOYSA-N 0.000 claims description 4
- 239000008107 starch Substances 0.000 claims description 4
- 235000019698 starch Nutrition 0.000 claims description 4
- 239000005720 sucrose Substances 0.000 claims description 4
- CZMRCDWAGMRECN-UGDNZRGBSA-N Sucrose Chemical compound O[C@H]1[C@H](O)[C@@H](CO)O[C@@]1(CO)O[C@@H]1[C@H](O)[C@@H](O)[C@H](O)[C@@H](CO)O1 CZMRCDWAGMRECN-UGDNZRGBSA-N 0.000 claims description 3
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 3
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 3
- 238000004519 manufacturing process Methods 0.000 claims 1
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 23
- 229910001416 lithium ion Inorganic materials 0.000 abstract description 23
- 238000009792 diffusion process Methods 0.000 abstract description 12
- 238000012986 modification Methods 0.000 abstract description 10
- 230000004048 modification Effects 0.000 abstract description 10
- 238000007086 side reaction Methods 0.000 abstract description 6
- 238000005253 cladding Methods 0.000 abstract description 5
- 230000002195 synergetic effect Effects 0.000 abstract description 3
- 239000006183 anode active material Substances 0.000 abstract 1
- 238000010438 heat treatment Methods 0.000 description 33
- 239000002002 slurry Substances 0.000 description 18
- 239000000203 mixture Substances 0.000 description 17
- 239000004576 sand Substances 0.000 description 16
- 238000001354 calcination Methods 0.000 description 14
- 238000001816 cooling Methods 0.000 description 14
- 238000007873 sieving Methods 0.000 description 14
- 239000011248 coating agent Substances 0.000 description 10
- 238000000576 coating method Methods 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 10
- 239000007788 liquid Substances 0.000 description 10
- 239000006185 dispersion Substances 0.000 description 9
- 239000002994 raw material Substances 0.000 description 8
- 238000005303 weighing Methods 0.000 description 7
- 239000007864 aqueous solution Substances 0.000 description 6
- 239000010406 cathode material Substances 0.000 description 6
- 239000003792 electrolyte Substances 0.000 description 6
- 239000005696 Diammonium phosphate Substances 0.000 description 5
- 239000012298 atmosphere Substances 0.000 description 4
- 230000000694 effects Effects 0.000 description 4
- 230000008569 process Effects 0.000 description 4
- 238000005260 corrosion Methods 0.000 description 3
- 230000007797 corrosion Effects 0.000 description 3
- 230000006872 improvement Effects 0.000 description 3
- 238000001000 micrograph Methods 0.000 description 3
- 239000000243 solution Substances 0.000 description 3
- 229910010710 LiFePO Inorganic materials 0.000 description 2
- 229910019142 PO4 Inorganic materials 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 description 2
- 238000009826 distribution Methods 0.000 description 2
- 150000002500 ions Chemical class 0.000 description 2
- 230000014759 maintenance of location Effects 0.000 description 2
- 229910021645 metal ion Inorganic materials 0.000 description 2
- 238000013508 migration Methods 0.000 description 2
- 230000005012 migration Effects 0.000 description 2
- 239000012299 nitrogen atmosphere Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 239000010452 phosphate Substances 0.000 description 2
- NBIIXXVUZAFLBC-UHFFFAOYSA-K phosphate Chemical compound [O-]P([O-])([O-])=O NBIIXXVUZAFLBC-UHFFFAOYSA-K 0.000 description 2
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 1
- 229910000147 aluminium phosphate Inorganic materials 0.000 description 1
- QVGXLLKOCUKJST-UHFFFAOYSA-N atomic oxygen Chemical compound [O] QVGXLLKOCUKJST-UHFFFAOYSA-N 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 230000007123 defense Effects 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 239000005002 finish coating Substances 0.000 description 1
- 239000000446 fuel Substances 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 230000003446 memory effect Effects 0.000 description 1
- 238000003801 milling Methods 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000001301 oxygen Substances 0.000 description 1
- 229910052760 oxygen Inorganic materials 0.000 description 1
- 239000002245 particle Substances 0.000 description 1
- 239000000843 powder Substances 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 229910052761 rare earth metal Inorganic materials 0.000 description 1
- 238000000859 sublimation Methods 0.000 description 1
- 230000008022 sublimation Effects 0.000 description 1
- 125000000185 sucrose group Chemical group 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Images
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/364—Composites as mixtures
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/362—Composites
- H01M4/366—Composites as layered products
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/628—Inhibitors, e.g. gassing inhibitors, corrosion inhibitors
-
- 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 provides a modified lithium iron phosphate anode material, a preparation method and application thereof. The modified lithium iron phosphate positive electrode material comprises a lithium iron phosphate doping material and aluminum dihydrogen phosphate coated on the surface of the doping material; wherein the lithium iron phosphate doping material is a lanthanum and fluorine doped lithium iron phosphate material, and the chemical general formula is Li 1‑a+b Fe 1‑a PO 4 La a F b Wherein a is more than or equal to 0.0004 and less than or equal to 0.03,0.0004 and b is more than or equal to 0.03. The invention can ensure that the modified lithium iron phosphate anode active material has good consistency of electrochemical performance, reduces the residual lithium quantity on the surface, inhibits the surface side reaction, remarkably improves the electron conductivity and the lithium ion diffusion rate, and simultaneously has remarkably improved tap density and low temperature resistance through the synergistic effect of doping and cladding double modification.
Description
Technical Field
The invention relates to the technical field of lithium ion batteries, in particular to a modified lithium iron phosphate positive electrode material, a preparation method and application thereof.
Background
With the rapid development of social economy, modern science and technology and information industrialization, more and more new electronic products are widely applied in different fields, and environmentally friendly batteries and related industries thereof play an increasingly important role in a high-tech industrial chain. The lithium iron phosphate material has the characteristics of good safety performance, light weight, large energy storage, long service life, excellent cycle performance, environmental friendliness, wide raw material sources and the like, is recognized as one of the most important positive electrode materials of a new generation of lithium ion battery, and is widely applied to power supply, electric tools, lamps, meters, communication, automobile electronics and part of national defense industry fields. The high-energy lithium iron phosphate battery industry is rapidly growing, being pulled by the markets of electric tools, electric vehicles and hybrid electric vehicles.
Lithium iron phosphate (LiFePO) having an olivine structure 4 ) The lithium ion battery has the advantages of stable working voltage (3.4V), higher specific capacity (170 mAh/g), high discharge power, quick charge, long cycle life, no memory effect, good stability in high-temperature and high-heat environments and the like, and occupies a large component in the anode material of the lithium ion battery. Although LiFePO 4 The advantages are very obvious, but at the same time there are serious drawbacks such as: the electron conductivity and the lithium ion diffusion rate are lower, the tap density is lower, the low temperature resistance is poorer, and the like, which affects the LiFePO to a certain extent 4 Is used for the market application of (a).
Disclosure of Invention
The invention mainly aims to provide a modified lithium iron phosphate positive electrode material, a preparation method and application thereof, and aims to solve the problems of at least one of low electron conductivity and lithium ion diffusion rate, low tap density and poor low temperature resistance of the lithium iron phosphate material in the prior art.
In order to achieve the above object, according to one aspect of the present invention, there is provided a modified lithium iron phosphate cathode material comprising a lithium iron phosphate dopant and aluminum dihydrogen phosphate coated on the surface thereof; wherein the lithium iron phosphate doping material is a lanthanum and fluorine doped lithium iron phosphate material, and the chemical general formula is Li 1-a+b Fe 1-a PO 4 La a F b Wherein a is more than or equal to 0.0004 and less than or equal to 0.03,0.0004 and b is more than or equal to 0.03.
Further, a is more than or equal to 0.0004 and less than or equal to 0.0025,0.0004, b is more than or equal to 0.0025; and/or the tap density of the modified lithium iron phosphate positive electrode material is more than or equal to 1.25g/cm 3 。
According to another aspect of the present invention, there is provided a method for preparing the modified lithium iron phosphate positive electrode material according to the present invention, comprising the steps of: step S1, mixing a lithium source, an iron source, a phosphorus source, a lanthanum source, a fluorine source and a carbon source with water, and sequentially carrying out first grinding and drying to obtain a mixed material A; s2, performing first sintering on the mixed material A to obtain a lithium iron phosphate doping material; step S3, mixing the lithium iron phosphate doping material with an aluminum dihydrogen phosphate precursor, and then carrying out second grinding to obtain a mixed material B; and S4, performing second sintering on the mixed material B to obtain the modified lithium iron phosphate anode material.
Further, the weight ratio of the lithium iron phosphate doping material to the aluminum dihydrogen phosphate precursor is 100 (0.35-6.5); preferably, the aluminum dihydrogen phosphate precursor includes aluminum phosphate and diammine hydrogen phosphate; more preferably, the weight ratio of aluminum phosphate to diammonium phosphate is (0.0005-0.005): 0.003-0.06.
Further, in step S1, the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate; and/or the iron source is ferric phosphate; and/or the phosphorus source is ferric phosphate; and/or the lanthanum source is one or more of lanthanum oxide, lanthanum acetate and lanthanum carbonate; and/or the fluorine source is one or more of lithium fluoride, sodium fluoride and potassium fluoride; and/or the carbon source is one or more of glucose, sucrose, starch, cyclodextrin and citric acid.
Further, in the step S1, the first grinding mode is sanding, the rotating speed is 100-800 r/min, and the time is 1-6 h; and/or the drying mode is spray drying, the air inlet temperature is 280-380 ℃, and the drying time is 1-6 h.
Further, in step S2, the first sintering is performed in an inert gas atmosphere, and the inert gas is nitrogen and/or argon; and/or the temperature rising rate of the first sintering is 1-10 ℃/min, the sintering temperature is 600-800 ℃, and the sintering time is 6-15 h.
Further, in the step S3, the second grinding mode is ball milling, the rotating speed is 100-800 r/min, and the time is 1-6 h.
Further, in step S4, the second sintering is performed in an inert gas atmosphere, wherein the inert gas is nitrogen and/or argon; and/or the temperature rising rate of the second sintering is 1-10 ℃/min, the sintering temperature is 500-780 ℃, and the sintering time is 6-10 h.
According to another aspect of the present invention, there is provided a battery comprising a positive electrode material comprising the modified lithium iron phosphate positive electrode material of the present invention described above, or a modified lithium iron phosphate positive electrode material obtained using the preparation method of the present invention described above.
By adopting the technical scheme, la and F are doped, so that the surface of the lithium iron phosphate material has good lithium ion conduction characteristic and electron conduction characteristic, and the interplanar spacing can be increased, thereby improving the tap density. Meanwhile, the surface of the lithium iron phosphate doping material is coated with aluminum dihydrogen phosphate, so that the corrosion of the electrolyte to the surface of the positive electrode material can be effectively resisted, the side reaction between the positive electrode material and the electrolyte is avoided, and the low temperature resistance and the cycle performance of the lithium iron phosphate material are improved. In conclusion, the modified lithium iron phosphate positive electrode active material has La and F doping modification and aluminum dihydrogen phosphate cladding modification, and the electrochemical performance consistency of the modified lithium iron phosphate positive electrode active material is good through the synergistic effect of doping and cladding modification, the residual lithium amount on the surface is reduced, the surface side reaction is inhibited, the electron conductivity and the lithium ion diffusion rate are remarkably improved, and meanwhile, the tap density and the low temperature resistance are remarkably improved.
Drawings
The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and together with the description serve to explain the invention. In the drawings:
FIG. 1 shows a scanning electron microscope image of a modified lithium iron phosphate positive electrode material according to example 1 of the present invention;
fig. 2 shows a scanning electron microscope image of a lithium iron phosphate positive electrode material according to comparative example 1; and
fig. 3 shows a scanning electron microscope image of a lithium iron phosphate positive electrode material according to comparative example 2.
Detailed Description
It should be noted that, in the case of no conflict, the embodiments and features in the embodiments may be combined with each other. The invention will be described in detail below with reference to the drawings in connection with embodiments.
As described in the background art of the invention, the problems of lower electron conductivity and lithium ion diffusion rate, lower tap density or poorer low temperature resistance of the lithium iron phosphate material exist in the prior art. In order to solve the above problems, in an exemplary embodiment of the present invention, there is provided a modified lithium iron phosphate cathode material including a lithium iron phosphate dopant and aluminum dihydrogen phosphate coated on the surface thereof; wherein the lithium iron phosphate doping material is a lanthanum and fluorine doped lithium iron phosphate material, and the chemical general formula is Li 1-a+b Fe 1-a PO 4 La a F b Wherein a is more than or equal to 0.0004 and less than or equal to 0.03,0.0004 and b is more than or equal to 0.03.
The lithium iron phosphate doping material has the advantages that lanthanum and fluorine elements are doped in a specific proportion, the interplanar spacing can be increased, so that lithium ion migration is promoted, and a chemical bond formed by the lithium iron phosphate doping material and metal ions in a lithium iron phosphate material is firmer, so that the stability of a material structure is improved, the tap density and low temperature resistance of a modified lithium iron phosphate positive electrode material are improved, and the electronic conductivity and the lithium ion diffusion rate are improved. It should be noted that, unexpectedly, the inventors found that only doping lanthanum element can reduce the unit cell parameters of the modified material, and the cells shrink, so that the stability of the material is facilitated, and other rare earth elements cannot realize the above properties of the invention.
Meanwhile, the surface of the lithium iron phosphate doping material has specific phosphate coating, and the surface of the material has better lithium ion conduction characteristic and certain electron conductivity characteristic, so that the lithium iron phosphate doping material has higher lithium removal state stability under high voltage. The aluminum dihydrogen phosphate coating can effectively resist the corrosion of the electrolyte to the surface of the positive electrode material, avoid the side reaction between the positive electrode material and the electrolyte, and further improve the modified lithium iron phosphate positive electrode materialTap density, electron conductivity and lithium ion diffusion rate, and improves low temperature resistance and cycle performance. When the modified lithium iron phosphate positive electrode material is used for a positive electrode plate, the compaction density of the plate can reach 2.65g/cm 3 The discharge capacity retention rate of the soft package battery prepared by the method can reach 90% at the temperature of minus 20 ℃, and the low temperature resistance of the battery is obviously improved.
In a preferred embodiment, 0.0004. Ltoreq.a.ltoreq. 0.0025,0.0004. Ltoreq.b.ltoreq.0.0025, most preferably the modified lithium iron phosphate positive electrode material is Li 1.0021 Fe 0.9996 PO 4 La 0.0004 F 0.0025 The method comprises the steps of carrying out a first treatment on the surface of the And/or the tap density of the modified lithium iron phosphate positive electrode material is more than or equal to 1.25g/cm 3 Such as 1.25 to 3g/cm 3 The modified lithium iron phosphate anode material under the conditions has better low temperature resistance and cycle performance.
In still another exemplary embodiment of the present invention, there is also provided a method for preparing the above modified lithium iron phosphate positive electrode material, including the steps of: step S1, mixing a lithium source, an iron source, a phosphorus source, a lanthanum source, a fluorine source and a carbon source with water, and sequentially carrying out first grinding and drying to obtain a mixed material A; s2, performing first sintering on the mixed material A to obtain a lithium iron phosphate doping material; step S3, mixing the lithium iron phosphate doping material with an aluminum dihydrogen phosphate precursor, and then carrying out second grinding to obtain a mixed material B; and S4, performing second sintering on the mixed material B to obtain the modified lithium iron phosphate anode material.
Firstly mixing a lithium source, an iron source, a phosphorus source, a lanthanum source, a fluorine source and a carbon source with water, primarily dispersing in the water, then sequentially carrying out first grinding and drying, and uniformly mixing to obtain a mixed material A; and secondly, performing first sintering on the mixed material A to enable lanthanum and fluorine to further enter the lithium iron phosphate material to be doped, mixing the mixed material A with an aluminum dihydrogen phosphate precursor after obtaining the lithium iron phosphate doping material, performing second grinding, and uniformly mixing to obtain the mixed material B, performing second sintering, wherein a carbon source is used as fuel, and enabling the aluminum dihydrogen phosphate to be coated on the surface of the lithium iron phosphate doping material to obtain the modified lithium iron phosphate anode material.
According to the invention, lanthanum and fluorine are doped in the process of preparing the lithium iron phosphate doping material, so that lanthanum and fluorine enter the cathode material, the distribution uniformity of doped ions in the cathode material is ensured, the interplanar spacing can be increased, thereby promoting lithium ion migration, enabling chemical bonds formed by the doped ions and metal ions in the cathode material to be firmer, doping lanthanum and fluorine not only can promote sintering, enable the structure to be more uniform, but also can promote the stability of the material structure, and improve the tap density, low temperature resistance and electron conductivity and lithium ion diffusion rate of the lithium iron phosphate. And then preparing the modified lithium iron phosphate anode material by coating aluminum dihydrogen phosphate on the surface, so that the surface of the material has better lithium ion conduction characteristic and certain electron conduction characteristic, and has higher lithium removal state stability under high voltage. The preparation process is simple, the operation is convenient, the industrial production is easy to realize, and the preparation method has wide application prospect.
In order to achieve the purpose of enabling the aluminum dihydrogen phosphate to finish coating on the surface of the lithium iron phosphate doping material and simultaneously avoiding excessive coating on the surface of the doping material to reduce the capacity of the positive electrode material, thereby further improving the electronic conductivity and the lithium ion diffusion rate of the material, in a preferred embodiment, in the step S3, the weight ratio of the lithium iron phosphate doping material to the aluminum dihydrogen phosphate precursor is 100 (0.35-6.5); preferably, the aluminum dihydrogen phosphate precursor comprises aluminum phosphate and diammonium hydrogen phosphate, and the diammonium hydrogen phosphate is decomposed at high temperature to generate phosphoric acid during sintering, and reacts with the aluminum phosphate to generate aluminum dihydrogen phosphate for coating. More preferably, the weight ratio of the aluminum phosphate to the diammonium hydrogen phosphate is (0.0005-0.005): (0.003-0.06), the coating reaction is more sufficient, and the coating modification effect of the material is better. In the specific preparation process, the aluminum phosphate and the diammonium phosphate can be added in the form of an aqueous solution, and preferably the diammonium phosphate solution is an aqueous solution with the mass percent of the diammonium phosphate of 20-40%, so that the coating is more uniform.
For the purpose of further improving the stability of the lithium iron phosphate dopant, thereby further improving the tap density, low temperature resistance, and electron conductivity and lithium ion diffusion rate of the lithium iron phosphate, in a preferred embodiment, in step S1, the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium nitrate, and lithium acetate; and/or the iron source is ferric phosphate; and/or the phosphorus source is ferric phosphate; and/or the lanthanum source is one or more of lanthanum oxide, lanthanum acetate and lanthanum carbonate; and/or the fluorine source is one or more of lithium fluoride, sodium fluoride and potassium fluoride; and/or the carbon source is one or more of glucose, sucrose, starch, cyclodextrin and citric acid, and the raw materials can further reduce the preparation cost. Wherein, each raw material is added according to the element stoichiometric ratio of the modified lithium iron phosphate positive electrode material, and the raw materials are understood by those skilled in the art and are not described herein. Wherein the lithium source can be added in an amount of 1.0 to 1.15 times the stoichiometric ratio, thereby further compensating for the loss caused by sublimation of lithium in high temperature sintering.
According to the invention, a specific grinding and dispersing process is adopted, so that the particle size distribution of the lithium iron phosphate doping material is more uniform, in a preferred embodiment, in the step S1, the first grinding mode is grinding, the rotating speed is 100-800 r/min, the time is 1-6 h, and the dispersing effect is better; and/or the drying mode is spray drying, the air inlet temperature is 100-150 ℃, the drying time is 1-6 h, the drying rate is high, and the materials can be dried more uniformly.
Accordingly, in a preferred embodiment, in step S3, the second milling is performed by ball milling at a rotational speed of 100-800 r/min for a period of 1-6 hours, so that the materials are more thoroughly mixed.
In a preferred embodiment, in step S2, the first sintering is performed in an inert gas atmosphere, where the inert gas is nitrogen and/or argon, so that the oxidation side effects of oxygen and the like on the material or raw material can be avoided; and/or the heating rate of the first sintering is 1-10 ℃/min, the sintering temperature is 600-800 ℃ and the sintering time is 6-15 h, so that the raw material is in a liquid state, and the generation of lithium iron phosphate is facilitated. Meanwhile, as described above, lanthanum and fluorine elements are doped in the material of the invention, so that sintering can be promoted, and more sufficient sintering can be realized by using a lower sintering temperature and a shorter sintering time, and a material with uniform structure can be obtained.
For similar reasons, in a preferred embodiment, in step S4, the second sintering is performed in an inert gas atmosphere, the inert gas being nitrogen and/or argon; and/or the temperature rising rate of the second sintering is 1-10 ℃/min, the sintering temperature is 500-780 ℃ and the sintering time is 6-10 h, thereby being more beneficial to the full coating of the aluminum dihydrogen phosphate on the surface of the lithium iron phosphate doping material.
Typically, but not limited to, in the above lithium iron phosphate dopant, a is a range of values consisting of 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.027, 0.028, 0.029, 0.03, or any two thereof. b is a range of values consisting of 0.0005, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, 0.021, 0.022, 0.023, 0.024, 0.025, 0.026, 0.027, 0.028, 0.029, 0.03, or any two thereof.
Typical, but not limiting, methods of preparing the modified lithium iron phosphate positive electrode material include a weight ratio of lithium iron phosphate dopant to aluminum dihydrogen phosphate precursor of 100:0.35, 100:0.5, 100:1, 100:1.5, 100:2, 100:2.5, 100:3, 100:3.5, 100:4, 100:4.5, 100:5, 100:5.5, 100:6, 100:6.5, or any two ratio ranges thereof.
Typically, but not by way of limitation, the above-mentioned aluminum phosphate, diammine hydrogen phosphate and lithium iron phosphate dopants are present in the following values or in the range of values consisting of any two of these values: the mass of the lithium iron phosphate doping material is 1, and the aluminum phosphate is 0.0005, 0.001, 0.0015, 0.002, 0.0025, 0.003, 0.0035, 0.004, 0.0045 and 0.005; diammonium phosphate is 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, 0.015, 0.02, 0.025, 0.03, 0.035, 0.04, 0.045, 0.05, 0.055, 0.06.
Typically, but not limited to, the spray drying inlet temperature is 280 ℃, 290 ℃, 300 ℃, 310 ℃, 320 ℃, 330 ℃, 340 ℃, 350 ℃, 360 ℃, 370 ℃, 380 ℃ or any two values thereof, and the drying time is 1h, 2h, 3h, 4h, 5h, 6h or any two values thereof.
Typically, but not limited to, the sintering temperature of the first sintering is 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃, 700 ℃, 720 ℃, 740 ℃, 760 ℃, 780 ℃, 800 ℃ or any two values thereof, and the sintering time is 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h or any two values thereof.
Typically, but not limited to, the second sintering is performed at a sintering temperature of 500 ℃, 520 ℃, 540 ℃, 560 ℃, 580 ℃, 600 ℃, 620 ℃, 640 ℃, 660 ℃, 680 ℃, 700 ℃, 720 ℃, 740 ℃, 760 ℃, 780 ℃ or any two values thereof, and a sintering time of 6h, 7h, 8h, 9h, 10h or any two values thereof.
In still another exemplary embodiment of the present invention, there is also provided a battery including the positive electrode material including the modified lithium iron phosphate positive electrode material of the present invention, or the modified lithium iron phosphate positive electrode material obtained using the above-described preparation method of the present invention. The electronic conductivity and the lithium ion diffusion rate of the battery can be obviously improved, and the tap density and the low temperature resistance of the material are improved.
The present application is described in further detail below in conjunction with specific embodiments, which should not be construed as limiting the scope of the claims.
Example 1
Step S1: weighing anhydrous ferric phosphate and La according to the molar ratio of 1:0.0008:0.025:0.001:1.05 2 O 3 LiF, glucose, li 2 CO 3 And adding the mixture into dispersion liquid (water) for sanding after uniformly mixing, wherein the sanding speed is 300r/min, and the time is 3h, so as to obtain sanding slurry. Spray drying the sanded slurry, wherein the air inlet temperature of the spray drying is 300 ℃ and the air inlet time is 3 hours, so as to obtain a mixed material A;
step S2: in a nitrogen environment, placing the mixed material A in a muffle furnace, heating to 770 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, and then self-heatingThen cooling to room temperature, grinding, crushing and sieving to obtain the lithium iron phosphate doping material, wherein the chemical formula of the obtained lithium iron phosphate doping material is Li 1.0021 Fe 0.9996 PO 4 La 0.0004 F 0.0025 ；
Step S3: mixing aluminum phosphate, diammine hydrogen phosphate and lithium iron phosphate doping materials according to a mass ratio of 0.003:0.015:1, and then ball-milling at a rotational speed of 300r/min for 5 hours to obtain a mixed material B, wherein the diammine hydrogen phosphate is added in the form of an aqueous solution, and the mass fraction of the diammine hydrogen phosphate is 30%;
step S4: and (3) in an inert gas environment, placing the mixed material B in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the modified lithium iron phosphate anode material.
Example 2
Step S1: weighing anhydrous ferric phosphate and La according to the molar ratio of 1:0.0008:0.025:0.001:1.05 2 O 3 LiF, glucose, li 2 CO 3 And adding the mixture into dispersion liquid (water) for sanding after uniformly mixing, wherein the sanding speed is 300r/min, and the time is 3h, so as to obtain sanding slurry. Spray drying the sanded slurry, wherein the air inlet temperature of the spray drying is 300 ℃ and the air inlet time is 3 hours, so as to obtain a mixed material A;
step S2: in an inert gas environment, placing the mixed material A in a muffle furnace, heating to 770 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, naturally cooling to room temperature, grinding, crushing and sieving to prepare the lithium iron phosphate doping material, wherein the chemical formula of the obtained lithium iron phosphate doping material is Li 1.0021 Fe 0.9996 PO 4 La 0.0004 F 0.0025 ；
Step S3: mixing aluminum phosphate, diammonium hydrogen phosphate solution and lithium iron phosphate doping material according to the mass ratio of 0.003:0.015:1, and then ball-milling at the speed of 300r/min for 5 hours to obtain a mixed material B, wherein diammonium hydrogen phosphate is added in the form of aqueous solution, and the mass fraction of diammonium hydrogen phosphate is 30%;
step S4: and (3) in an inert gas environment, placing the mixed material B in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the modified lithium iron phosphate anode material.
Example 3
Step S1, weighing anhydrous ferric phosphate and La according to the molar ratio of 1:0.0008:0.025:0.001:1.12 2 O 3 LiF, glucose, li 2 CO 3 And adding the mixture into dispersion liquid (water) for sanding after uniformly mixing, wherein the sanding speed is 300r/min, and the time is 3h, so as to obtain sanding slurry. Spray drying the sanded slurry, wherein the air inlet temperature of the spray drying is 300 ℃ and the air inlet time of the spray drying is 3 hours to obtain a mixed material A;
step S2: in an inert gas environment, placing the mixed material A in a muffle furnace, heating to 770 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, naturally cooling to room temperature, grinding, crushing and sieving to prepare the lithium iron phosphate doping material, wherein the chemical formula of the obtained lithium iron phosphate doping material is Li 1.0021 Fe 0.9996 PO 4 La 0.0004 F 0.0025 ；
Step S3: mixing aluminum phosphate, diammonium hydrogen phosphate solution and lithium iron phosphate doping material according to the mass ratio of 0.003:0.015:1, and then ball-milling at the speed of 300r/min for 5 hours to obtain a mixed material B, wherein diammonium hydrogen phosphate is added in the form of aqueous solution, and the mass fraction of diammonium hydrogen phosphate is 30%;
step S4: and (3) in an inert gas environment, placing the mixed material B in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the modified lithium iron phosphate anode material.
Example 4
Example 4 differs from example 1 in that the lithium source is lithium hydroxide, the iron source is ferric phosphate, the phosphorus source is ferric phosphate, the lanthanum source is lanthanum carbonate, the fluorine source is sodium fluoride, the carbon source is sucrose, and the chemical formula of the lithium iron phosphate dopant obtained in step S2 is LiFe 0.9996 PO 4 La 0.0004 F 0.03 。
Example 5
Example 5 and example1 is characterized in that the lithium source is lithium nitrate, the iron source is ferric phosphate, the phosphorus source is ferric phosphate, the lanthanum source is lanthanum acetate, the fluorine source is potassium fluoride, the carbon source is starch, and the chemical formula of the lithium iron phosphate doping material obtained in the step S2 is Li 1.0296 Fe 0.9996 PO 4 La 0.0004 F 0.03 。
Example 6
Example 6 differs from example 1 in that the lithium source is lithium acetate, the iron source is ferric phosphate, the phosphorus source is ferric phosphate, the lanthanum source is lanthanum carbonate, the fluorine source is sodium fluoride, the carbon source is cyclodextrin, and the chemical formula of the lithium iron phosphate dopant obtained in step S2 is Li 0.9704 Fe 0.97 PO 4 La 0.03 F 0.0004 。
Example 7
Example 7 differs from example 1 in that the lithium source is lithium hydroxide, the iron source is ferric phosphate, the phosphorus source is ferric phosphate, the lanthanum source is lanthanum carbonate, the fluorine source is sodium fluoride, the carbon source is citric acid, and the chemical formula of the lithium iron phosphate dopant obtained in step S2 is LiFe 0.97 PO 4 La 0.03 F 0.0004 。
Example 8
Example 8 differs from example 1 in that in step S1, the raw materials are added into the dispersion liquid (water) after being uniformly mixed, and sand is performed, the rotational speed of sand is 100r/min, and the time is 6h, so that sand slurry is obtained; and (3) carrying out spray drying on the sanded slurry, wherein the air inlet temperature of the spray drying is 280 ℃, and the time is 6 hours, so as to obtain a mixed material A.
Example 9
Example 9 differs from example 1 in that in step S1, the raw materials are added into the dispersion liquid (water) after being uniformly mixed, and sand is performed, the rotational speed of sand is 800r/min, and the time is 1h, so that sand slurry is obtained; and (3) carrying out spray drying on the sanded slurry, wherein the air inlet temperature of the spray drying is 380 ℃ and the time is 1h, so as to obtain a mixed material A.
Example 10
Example 10 differs from example 1 in that in step S2, in a nitrogen atmosphere, the mixture a is placed in a muffle furnace, heated to 600 ℃ at a heating rate of 1 ℃/min, calcined for 15 hours, then naturally cooled to room temperature, ground, crushed and sieved to prepare the lithium iron phosphate dopant.
Example 11
Example 11 differs from example 1 in that in step S2, in a nitrogen atmosphere, the mixture a is placed in a muffle furnace, heated to 800 ℃ at a heating rate of 10 ℃/min, calcined for 6 hours, then naturally cooled to room temperature, ground, crushed and sieved to prepare the lithium iron phosphate dopant.
Example 12
Example 12 differs from example 1 in that in step S3, aluminum phosphate, diammine hydrogen phosphate and lithium iron phosphate are mixed according to a mass ratio of 0.0005:0.003:1, and then ball-milled at a rotational speed of 100r/min for 6 hours to obtain a mixed material B.
Example 13
Example 13 differs from example 1 in that in step S3, aluminum phosphate, diammine hydrogen phosphate and lithium iron phosphate are mixed according to a mass ratio of 0.005:0.06:1, and then ball-milled at a rotational speed of 800r/min for 1h to obtain a mixed material B.
Example 14
Example 14 differs from example 1 in that in step S4, in an inert gas environment, the mixture B is placed in a tube furnace, heated to 500 ℃ from room temperature at a heating rate of 1 ℃/min, calcined for 10 hours, naturally cooled to room temperature, and then ground, crushed and sieved to prepare the modified lithium iron phosphate anode material.
Example 15
Example 15 differs from example 1 in that in step S4, in the inert gas environment, the mixture B is placed in a tube furnace, heated to 780 ℃ from room temperature at a heating rate of 10 ℃/min, calcined for 6 hours, naturally cooled to room temperature, and then ground, crushed and sieved to prepare the modified lithium iron phosphate anode material.
Comparative example 1
Step S1: weighing anhydrous ferric phosphate and Li according to a molar ratio of 1:0.53:0.001 2 CO 3 And glucose, adding the mixture into dispersion liquid (water) after uniformly mixing, and performing sand grinding, wherein the speed of sand grinding is 300r/min, and the time is 3h, so as to obtain sand grinding slurry. Will sand wellSpray drying the slurry at 300 deg.c for 3 hr to obtain mixture;
step S2: in an inert gas environment, placing the mixture in a muffle furnace, heating to 770 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, naturally cooling to room temperature, grinding, crushing and sieving to obtain a lithium iron phosphate material;
step S3: and (3) in an inert gas environment, placing the lithium iron phosphate material in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the lithium iron phosphate anode material.
Comparative example 2
Step S1: weighing anhydrous ferric phosphate and Li according to a molar ratio of 1:0.53:0.001 2 CO 3 And glucose, adding the mixture into dispersion liquid (water) after uniformly mixing, and performing sand grinding, wherein the speed of sand grinding is 300r/min, and the time is 3h, so as to obtain sand grinding slurry. Spray drying the sanded slurry, wherein the air inlet temperature of the spray drying is 300 ℃ and the air inlet time is 3 hours, so as to obtain a mixture;
step S2: in an inert gas environment, placing the mixture in a muffle furnace, heating to 760 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, naturally cooling to room temperature, grinding, crushing and sieving to obtain a lithium iron phosphate material;
step S3: and (3) in an inert gas environment, placing the lithium iron phosphate material in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the lithium iron phosphate anode material.
Comparative example 3
Step S1: weighing anhydrous ferric phosphate and Li according to a molar ratio of 1:0.53:0.001 2 CO 3 And glucose, adding the mixture into dispersion liquid (water) after uniformly mixing, and performing sand grinding, wherein the speed of sand grinding is 300r/min, and the time is 3h, so as to obtain sand grinding slurry. Spray drying the sanded slurry, wherein the air inlet temperature of the spray drying is 300 ℃ and the air inlet time is 3 hours, so as to obtain a mixture;
step S2: in an inert gas environment, placing the mixture in a muffle furnace, heating to 770 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, naturally cooling to room temperature, grinding, crushing and sieving to obtain a lithium iron phosphate material;
step S3: mixing aluminum phosphate, diammine hydrogen phosphate and lithium iron phosphate according to the mass ratio of 0.003:0.015:1, and then ball-milling at the speed of 300r/min for 5 hours to obtain a coated material, wherein the diammine hydrogen phosphate is added in the form of an aqueous solution, and the mass fraction of the diammine hydrogen phosphate is 30%;
step S4: and (3) in an inert gas environment, placing the coated material in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the single-coated modified lithium iron phosphate anode material.
Comparative example 4
Step S1: weighing anhydrous ferric phosphate and La according to the molar ratio of 1:0.0008:0.025:0.001:1.05 2 O 3 LiF, glucose, li 2 CO 3 And adding the mixture into dispersion liquid (water) for sanding after uniformly mixing, wherein the sanding speed is 300r/min, and the time is 3h, so as to obtain sanding slurry. Spray drying the sanded slurry, wherein the air inlet temperature of the spray drying is 300 ℃ and the air inlet time is 3 hours, so as to obtain a mixed material A;
step S2: in a nitrogen environment, placing the mixed material A in a muffle furnace, heating to 770 ℃ at a heating rate of 5 ℃/min, calcining for 10 hours, naturally cooling to room temperature, grinding, crushing and sieving to prepare the lithium iron phosphate doping material, wherein the chemical formula of the obtained lithium iron phosphate doping material is Li 1.0021 Fe 0.9996 PO 4 La 0.0004 F 0.0025 ；
Step S3: and (3) in an inert gas environment, placing the lithium iron phosphate doping material in a tube furnace, heating to 730 ℃ from room temperature at a heating rate of 5 ℃/min, calcining for 8 hours, naturally cooling to room temperature, and grinding, crushing and sieving to obtain the single doping modified lithium iron phosphate anode material.
The scanning electron microscope of the modified lithium iron phosphate positive electrode material obtained in example 1 is shown in fig. 1, the scanning electron microscope of the lithium iron phosphate positive electrode material obtained in comparative example 1 is shown in fig. 2, and the scanning electron microscope of the lithium iron phosphate positive electrode material obtained in comparative example 2 is shown in fig. 3.
The modified lithium iron phosphate cathode materials prepared in the above examples and comparative examples were prepared into 10Ah soft-pack full-electric lithium batteries, and the performance results thereof are shown in table 1.
Performance test:
tap density: tap density meter.
Electrochemical performance test: electrochemical workstation, charge-discharge voltage range: 2.0-3.65V.
TABLE 1
From the above, the modified lithium iron phosphate positive electrode material prepared by doping lanthanum and fluorine elements in the process of synthesizing the lithium iron phosphate doping material and coating phosphate on the surface has a remarkable improvement effect on increasing the tap density of lithium iron phosphate powder and increasing the discharge capacity retention rate of the battery at low temperature. The soft-package full-electric lithium battery prepared by the material in each embodiment of the invention has better performance than the undoped and/or uncoated material in the comparative example. Therefore, when the lithium iron phosphate positive electrode material prepared by the method is applied to a lithium ion battery, the tap density of the lithium iron phosphate can be improved, the improvement of the energy density of the battery is facilitated, and the low temperature resistance of the battery is also greatly improved.
From the above, according to the embodiments of the invention, la and F are doped, so that the surface of the lithium iron phosphate material has good lithium ion conduction characteristic and electron conduction characteristic, and the interplanar spacing can be increased, so that the tap density is improved. Meanwhile, the surface of the lithium iron phosphate doping material is coated with aluminum dihydrogen phosphate, so that the corrosion of the electrolyte to the surface of the positive electrode material can be effectively resisted, the side reaction between the positive electrode material and the electrolyte is avoided, and the low temperature resistance and the cycle performance of the lithium iron phosphate material are improved. In conclusion, the modified lithium iron phosphate positive electrode active material has La and F doping modification and aluminum dihydrogen phosphate cladding modification, and the electrochemical performance consistency of the modified lithium iron phosphate positive electrode active material is good through the synergistic effect of doping and cladding modification, the residual lithium amount on the surface is reduced, the surface side reaction is inhibited, the electron conductivity and the lithium ion diffusion rate are remarkably improved, and meanwhile, the tap density and the low temperature resistance are remarkably improved. In addition, it can be seen that the overall performance of the modified lithium iron phosphate positive electrode active material is better when each process parameter is within the preferred range of the present invention.
The above description is only of the preferred embodiments of the present invention and is not intended to limit the present invention, but various modifications and variations can be made to the present invention by those skilled in the art. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. The modified lithium iron phosphate anode material is characterized by comprising a lithium iron phosphate doping material and aluminum dihydrogen phosphate coated on the surface of the doping material;
wherein the lithium iron phosphate doping material is a lanthanum and fluorine doped lithium iron phosphate material, and the chemical general formula is
Li 1-a+b Fe 1-a PO 4 La a F b Wherein a is more than or equal to 0.0004 and less than or equal to 0.03,0.0004 and b is more than or equal to 0.03.
2. The modified lithium iron phosphate positive electrode material according to claim 1, wherein,
a is more than or equal to 0.0004 and less than or equal to 0.0025,0.0004, b is more than or equal to 0.0025; and/or
The tap density of the modified lithium iron phosphate positive electrode material is more than or equal to 1.25g/cm 3 。
3. The method for preparing a modified lithium iron phosphate positive electrode material according to claim 1 or 2, characterized by comprising the steps of:
step S1, mixing a lithium source, an iron source, a phosphorus source, a lanthanum source, a fluorine source and a carbon source with water, and sequentially carrying out first grinding and drying to obtain a mixed material A;
step S2, performing first sintering on the mixed material A to obtain a lithium iron phosphate doping material;
step S3, mixing the lithium iron phosphate doping material with an aluminum dihydrogen phosphate precursor, and then performing second grinding to obtain a mixed material B;
and S4, performing second sintering on the mixed material B to obtain the modified lithium iron phosphate anode material.
4. The method according to claim 3, wherein the weight ratio of the lithium iron phosphate dopant to the aluminum dihydrogen phosphate precursor is 100 (0.35-6.5);
preferably, the aluminum dihydrogen phosphate precursor includes aluminum phosphate and diammine hydrogen phosphate;
more preferably, the weight ratio of the aluminum phosphate to the diammonium hydrogen phosphate is (0.0005-0.005): 0.003-0.06.
5. The method according to claim 3 or 4, wherein in the step S1,
the lithium source is one or more of lithium hydroxide, lithium carbonate, lithium nitrate and lithium acetate; and/or
The iron source is ferric phosphate; and/or
The phosphorus source is ferric phosphate; and/or
The lanthanum source is one or more of lanthanum oxide, lanthanum acetate and lanthanum carbonate; and/or
The fluorine source is one or more of lithium fluoride, sodium fluoride and potassium fluoride; and/or
The carbon source is one or more of glucose, sucrose, starch, cyclodextrin and citric acid.
6. The method according to any one of claims 3 to 5, wherein in the step S1,
the first grinding mode is sanding, the rotating speed is 100-800 r/min, and the time is 1-6 h; and/or
The drying mode is spray drying, the air inlet temperature is 280-380 ℃, and the drying time is 1-6 h.
7. The method according to any one of claims 3 to 6, wherein in the step S2,
the first sintering is carried out in an inert gas environment, wherein the inert gas is nitrogen and/or argon; and/or
The temperature rising rate of the first sintering is 1-10 ℃/min, the sintering temperature is 600-800 ℃, and the sintering time is 6-15 h.
8. The method according to any one of claims 3 to 7, wherein in step S3, the second grinding is performed by ball milling at a rotational speed of 100 to 800r/min for 1 to 6 hours.
9. The method according to any one of claims 3 to 8, wherein in the step S4,
the second sintering is carried out in an inert gas environment, wherein the inert gas is nitrogen and/or argon; and/or
The temperature rising rate of the second sintering is 1-10 ℃/min, the sintering temperature is 500-780 ℃, and the sintering time is 6-10 h.
10. A battery comprising a positive electrode material, characterized in that the positive electrode material comprises the modified lithium iron phosphate positive electrode material according to claim 1 or 2, or a modified lithium iron phosphate positive electrode material obtained using the production method according to any one of claims 3 to 9.
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