CN115959644B - Method for preparing high-performance lithium iron phosphate by sectional sintering - Google Patents
Method for preparing high-performance lithium iron phosphate by sectional sintering Download PDFInfo
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- CN115959644B CN115959644B CN202211725757.8A CN202211725757A CN115959644B CN 115959644 B CN115959644 B CN 115959644B CN 202211725757 A CN202211725757 A CN 202211725757A CN 115959644 B CN115959644 B CN 115959644B
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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 65
- 238000000034 method Methods 0.000 title claims abstract description 35
- 238000005245 sintering Methods 0.000 title claims abstract description 22
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 59
- 229910052742 iron Inorganic materials 0.000 claims abstract description 27
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims abstract description 27
- 239000002243 precursor Substances 0.000 claims abstract description 27
- 239000005955 Ferric phosphate Substances 0.000 claims abstract description 26
- 238000001354 calcination Methods 0.000 claims abstract description 26
- 229940032958 ferric phosphate Drugs 0.000 claims abstract description 26
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims abstract description 26
- GWEVSGVZZGPLCZ-UHFFFAOYSA-N Titan oxide Chemical compound O=[Ti]=O GWEVSGVZZGPLCZ-UHFFFAOYSA-N 0.000 claims abstract description 24
- 239000002002 slurry Substances 0.000 claims abstract description 24
- 239000002019 doping agent Substances 0.000 claims abstract description 19
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 18
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 18
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 15
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 14
- 239000011574 phosphorus Substances 0.000 claims abstract description 14
- 239000004408 titanium dioxide Substances 0.000 claims abstract description 12
- 238000001035 drying Methods 0.000 claims abstract description 9
- 239000012298 atmosphere Substances 0.000 claims abstract description 8
- 230000008569 process Effects 0.000 claims abstract description 8
- 239000000203 mixture Substances 0.000 claims abstract description 6
- 239000002904 solvent Substances 0.000 claims abstract description 5
- 239000010405 anode material Substances 0.000 claims abstract description 4
- 238000002156 mixing Methods 0.000 claims abstract description 4
- 239000002245 particle Substances 0.000 claims description 17
- 238000010438 heat treatment Methods 0.000 claims description 14
- 238000000227 grinding Methods 0.000 claims description 10
- UQSXHKLRYXJYBZ-UHFFFAOYSA-N Iron oxide Chemical compound [Fe]=O UQSXHKLRYXJYBZ-UHFFFAOYSA-N 0.000 claims description 9
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 9
- 238000001694 spray drying Methods 0.000 claims description 9
- 239000002994 raw material Substances 0.000 claims description 8
- 239000002202 Polyethylene glycol Substances 0.000 claims description 7
- 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 7
- 229930006000 Sucrose Natural products 0.000 claims description 7
- XGZVUEUWXADBQD-UHFFFAOYSA-L lithium carbonate Chemical compound [Li+].[Li+].[O-]C([O-])=O XGZVUEUWXADBQD-UHFFFAOYSA-L 0.000 claims description 7
- 229910052808 lithium carbonate Inorganic materials 0.000 claims description 7
- 229920001223 polyethylene glycol Polymers 0.000 claims description 7
- 239000005720 sucrose Substances 0.000 claims description 7
- 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 6
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 6
- KWGKDLIKAYFUFQ-UHFFFAOYSA-M lithium chloride Chemical compound [Li+].[Cl-] KWGKDLIKAYFUFQ-UHFFFAOYSA-M 0.000 claims description 6
- IIPYXGDZVMZOAP-UHFFFAOYSA-N lithium nitrate Chemical compound [Li+].[O-][N+]([O-])=O IIPYXGDZVMZOAP-UHFFFAOYSA-N 0.000 claims description 6
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 6
- 229930091371 Fructose Natural products 0.000 claims description 3
- 239000005715 Fructose Substances 0.000 claims description 3
- RFSUNEUAIZKAJO-ARQDHWQXSA-N Fructose Chemical compound OC[C@H]1O[C@](O)(CO)[C@@H](O)[C@@H]1O RFSUNEUAIZKAJO-ARQDHWQXSA-N 0.000 claims description 3
- 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 3
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 3
- 229960005070 ascorbic acid Drugs 0.000 claims description 3
- 235000010323 ascorbic acid Nutrition 0.000 claims description 3
- 239000011668 ascorbic acid Substances 0.000 claims description 3
- 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 3
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 3
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 3
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 3
- SZVJSHCCFOBDDC-UHFFFAOYSA-N ferrosoferric oxide Chemical compound O=[Fe]O[Fe]O[Fe]=O SZVJSHCCFOBDDC-UHFFFAOYSA-N 0.000 claims description 3
- 239000008103 glucose Substances 0.000 claims description 3
- 229910001386 lithium phosphate Inorganic materials 0.000 claims description 3
- TWQULNDIKKJZPH-UHFFFAOYSA-K trilithium;phosphate Chemical compound [Li+].[Li+].[Li+].[O-]P([O-])([O-])=O TWQULNDIKKJZPH-UHFFFAOYSA-K 0.000 claims description 3
- 229960004887 ferric hydroxide Drugs 0.000 claims description 2
- IEECXTSVVFWGSE-UHFFFAOYSA-M iron(3+);oxygen(2-);hydroxide Chemical compound [OH-].[O-2].[Fe+3] IEECXTSVVFWGSE-UHFFFAOYSA-M 0.000 claims description 2
- YPJCVYYCWSFGRM-UHFFFAOYSA-H iron(3+);tricarbonate Chemical compound [Fe+3].[Fe+3].[O-]C([O-])=O.[O-]C([O-])=O.[O-]C([O-])=O YPJCVYYCWSFGRM-UHFFFAOYSA-H 0.000 claims description 2
- 239000004576 sand Substances 0.000 claims description 2
- 239000000463 material Substances 0.000 abstract description 25
- 239000013078 crystal Substances 0.000 abstract description 7
- 239000012535 impurity Substances 0.000 abstract description 4
- 238000002360 preparation method Methods 0.000 abstract description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 10
- JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 description 7
- 229960005191 ferric oxide Drugs 0.000 description 7
- 229910001416 lithium ion Inorganic materials 0.000 description 6
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 6
- 239000011248 coating agent Substances 0.000 description 4
- 238000000576 coating method Methods 0.000 description 4
- 238000001816 cooling Methods 0.000 description 4
- 238000004519 manufacturing process Methods 0.000 description 4
- 238000012986 modification Methods 0.000 description 4
- 230000004048 modification Effects 0.000 description 4
- 239000012299 nitrogen atmosphere Substances 0.000 description 4
- 238000002441 X-ray diffraction Methods 0.000 description 3
- 230000000052 comparative effect Effects 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 2
- 230000004075 alteration Effects 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000002425 crystallisation Methods 0.000 description 2
- 230000008025 crystallization Effects 0.000 description 2
- 230000007547 defect Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 2
- 230000002708 enhancing effect Effects 0.000 description 2
- 150000002506 iron compounds Chemical group 0.000 description 2
- 238000010902 jet-milling Methods 0.000 description 2
- 238000011031 large-scale manufacturing process Methods 0.000 description 2
- 238000003801 milling Methods 0.000 description 2
- 239000000843 powder Substances 0.000 description 2
- 230000001737 promoting effect Effects 0.000 description 2
- 238000010298 pulverizing process Methods 0.000 description 2
- 238000007670 refining Methods 0.000 description 2
- 230000003213 activating effect Effects 0.000 description 1
- 230000004888 barrier function Effects 0.000 description 1
- 230000005540 biological transmission Effects 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 239000003795 chemical substances by application Substances 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 230000001010 compromised effect Effects 0.000 description 1
- 238000000354 decomposition reaction Methods 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000009826 distribution Methods 0.000 description 1
- 239000007772 electrode material Substances 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
- 238000011156 evaluation Methods 0.000 description 1
- 238000001704 evaporation Methods 0.000 description 1
- 230000008020 evaporation Effects 0.000 description 1
- RAQDACVRFCEPDA-UHFFFAOYSA-L ferrous carbonate Chemical compound [Fe+2].[O-]C([O-])=O RAQDACVRFCEPDA-UHFFFAOYSA-L 0.000 description 1
- 238000001914 filtration Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 239000011261 inert gas Substances 0.000 description 1
- 230000002401 inhibitory effect Effects 0.000 description 1
- 238000009830 intercalation Methods 0.000 description 1
- 230000002687 intercalation Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 235000014413 iron hydroxide Nutrition 0.000 description 1
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- NCNCGGDMXMBVIA-UHFFFAOYSA-L iron(ii) hydroxide Chemical compound [OH-].[OH-].[Fe+2] NCNCGGDMXMBVIA-UHFFFAOYSA-L 0.000 description 1
- 229910021645 metal ion Inorganic materials 0.000 description 1
- 230000000877 morphologic effect Effects 0.000 description 1
- 229910052757 nitrogen Inorganic materials 0.000 description 1
- 230000006911 nucleation Effects 0.000 description 1
- 238000010899 nucleation Methods 0.000 description 1
- 238000011056 performance test Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 239000011164 primary particle Substances 0.000 description 1
- 239000008213 purified water Substances 0.000 description 1
- 230000009257 reactivity Effects 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000001878 scanning electron micrograph Methods 0.000 description 1
- 238000004626 scanning electron microscopy Methods 0.000 description 1
- 238000001228 spectrum Methods 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
Classifications
-
- 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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- Battery Electrode And Active Subsutance (AREA)
Abstract
The application discloses a method for preparing high-performance lithium iron phosphate by sectional sintering, which is characterized by comprising the following steps: s1, mixing ferric phosphate dihydrate, a lithium source, a phosphorus source, a carbon source, titanium dioxide and an iron source doping agent in a solvent, and sanding the mixture to obtain slurry; s2, drying the slurry to obtain a lithium iron phosphate precursor; s3, carrying out three-stage high-temperature sectional calcination on the lithium iron phosphate precursor under an inert atmosphere, and then crushing to obtain the high-rate lithium iron phosphate anode material. According to the application, the ferric phosphate precursor ferric phosphate dihydrate is selected as a main iron source, so that the precursor preparation step is omitted, the industrial cost is reduced, the proper iron source doping agent is added, new impurities are not introduced, the electrical property of the material is improved, the sectional sintering process is adopted, the crystal grains are refined, and the comprehensive property of the lithium iron phosphate material is further improved.
Description
Technical Field
The invention belongs to the technical field of lithium ion batteries, and particularly relates to a method for preparing high-performance lithium iron phosphate by sectional sintering.
Background
The lithium ion battery is used as one of the market products of new energy technology, and is widely applied in the fields of automobile power, large-scale energy storage, portable equipment and the like at present. Lithium iron phosphate has become the mainstream lithium ion battery positive electrode material by virtue of its excellent structural stability, ultra-long cycle life, excellent safety performance and environmental protection. However, with the application of lithium iron phosphate in the power field, the electrochemical performance of the lithium iron phosphate is difficult to meet the market demand, and the improvement of the electrical performance of the lithium iron phosphate material on the premise of mass production is the key point of future development.
The lithium iron phosphate material is safe, environment-friendly, low in price, high in theoretical capacity as an electrode material, good in structural stability and long in cycle life. However, the material has poor conductivity and low lithium removing/inserting capability, which results in actual capacity lower than theoretical value, and carbon coating and metal ion doping can effectively improve the conductivity of lithium iron phosphate and increase the specific charge and discharge capacity of the lithium iron phosphate. The lithium iron phosphate material developed by the carbothermic reduction method in the iron phosphate process has excellent performance and higher compaction density, but the multiplying power performance of the lithium iron phosphate material is still difficult to meet the requirements of the power market.
Disclosure of Invention
The invention aims to provide a method for preparing high-performance lithium iron phosphate by sectional sintering in order to solve the defects in the prior art.
The invention aims at realizing the following technical scheme:
A method for preparing high-performance lithium iron phosphate by sectional sintering comprises the following steps:
s1, mixing ferric phosphate dihydrate, a lithium source, a phosphorus source, a carbon source, titanium dioxide and an iron source doping agent in a solvent, and sanding the mixture to obtain slurry; the iron source doping agent accounts for 500-10000 ppm of the mass of the finished product; the iron source dopant is an iron compound containing one or more elements of C, H, O;
S2, drying the slurry to obtain a lithium iron phosphate precursor;
S3, carrying out high-temperature sectional calcination on the lithium iron phosphate precursor in an inert atmosphere, and then crushing to obtain a high-rate lithium iron phosphate anode material; the high-temperature sectional calcination process comprises the following steps:
(4) Preserving heat for 2-4 h at 260-290 ℃;
(5) Preserving heat for 2-3 h at 620-680 ℃;
(6) Preserving heat for 5-7 h at 720-800 ℃.
Preferably, in the step S1, the molar ratio of total lithium, total iron and total phosphorus in the total raw materials is (1.00-1.20): (0.93-0.99): 1.
Preferably, the lithium source is one or a combination of more selected from lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, lithium chloride and lithium dihydrogen phosphate; the phosphorus source is one or a combination of more selected from phosphoric acid, ferric phosphate, lithium dihydrogen phosphate and diammonium hydrogen phosphate.
Preferably, the carbon source is one or more selected from glucose, sucrose, fructose, polyethylene glycol, ascorbic acid.
Preferably, the iron source dopant in step S1 is one or more selected from iron oxide red, iron oxide yellow, iron oxide black, iron hydroxide, and iron carbonate.
Preferably, the particle size of the slurry D50 is controlled to be 0.30-0.45 μm after the sand grinding in the step S1.
Preferably, the total consumption of the carbon source in the step S1 accounts for 10-20% of the mass of the finished lithium iron phosphate, and the consumption of the titanium dioxide accounts for 1000-5000 ppm of the mass of the finished product.
Preferably, spray drying is adopted in the step S2, the air inlet temperature is 180-250 ℃, and the air outlet temperature is 80-110 ℃.
Preferably, the three-stage heating rate of the high-temperature sectional calcination in the step S3 is respectively 1-5 ℃/min, 1-5 ℃/min and 3-15 ℃/min.
Preferably, the pulverizing mode in the step S3 is jet milling, and the particle diameter D50 after the milling is controlled to be 0.8-1.5 μm.
According to the application, the ferric phosphate precursor ferric phosphate dihydrate is selected as a main iron source, so that the precursor preparation step is omitted, the industrial cost is reduced, the proper iron source doping agent is added, new impurities are not introduced, the electrical property of the material is improved, the sectional sintering process is adopted, the crystal grains are refined, and the comprehensive property of the lithium iron phosphate material is further improved. The method is simple to operate, easy to implement and convenient for large-scale production, can directly improve production on the basis of the existing ferric phosphate process, and is suitable for large-scale popularization and use.
Drawings
FIG. 1 is an SEM image of the finished lithium iron phosphate of example 1;
fig. 2 is an XRD pattern of the finished lithium iron phosphate product of example 1.
Detailed Description
The invention provides a method for preparing high-performance lithium iron phosphate by sectional sintering, which comprises the following steps:
S1, mixing ferric phosphate dihydrate, a lithium source, a phosphorus source, a carbon source, titanium dioxide and an iron source doping agent in a solvent, and sanding the mixture to obtain slurry; the iron source doping agent accounts for 500-10000 ppm of the mass of the finished product; the iron source dopant is an iron compound containing one or more elements of C, H, O;
S2, drying the slurry to obtain a lithium iron phosphate precursor;
s3, carrying out high-temperature sectional calcination on the lithium iron phosphate precursor in an inert atmosphere, and then crushing to obtain a high-rate lithium iron phosphate anode material; the high-temperature sectional calcination procedure is as follows:
(7) Preserving heat for 2-4 h at 260-290 ℃;
(8) Preserving heat for 2-3 h at 620-680 ℃;
(9) Preserving heat for 5-7 h at 720-800 ℃.
According to the application, the ferric phosphate dihydrate and the ferric source doping agent are adopted as the ferric source, wherein the ferric phosphate dihydrate is the ferric phosphate precursor, and the ferric phosphate is selected as the ferric source, so that the steps of flash evaporation, roasting, crushing and the like for preparing the ferric phosphate are omitted, and by virtue of the morphological characteristics of small particle size and high dispersity, the synthesis time of the lithium iron phosphate is shortened, the industrial cost is saved, and meanwhile, the influence of the precursor shape, particle size and the like on a final finished product can be lightened. The main element of the doping agent is Fe, the other elements are O, H, C and the like, and other impurities are not introduced into the finished lithium iron phosphate product after high-temperature reaction. The selected doping agent and ferric phosphate dihydrate are the same as the iron source, but because of different reactivity, local defects are formed in the synthesized lithium iron phosphate material, so that the charge and discharge performance of the material is enhanced. Titanium dioxide is added into the raw materials, so that the method has the advantages of inhibiting grain growth, improving the conductivity of the material and improving the low-temperature performance of the material. And then sanding to fully disperse and uniformly mix the raw material slurry, refining the precursor particles and finishing uniform coating of the precursor by a carbon source, thereby being beneficial to obtaining a product with proper particle size after calcination. And drying and calcining to obtain a lithium iron phosphate product.
The method adopts a sectional gradient calcination mode, and has the advantages of enhancing the coating effect of the carbon layer and refining grains. The first stage sintering serves to evaporate the water of crystallization in the ferric phosphate dihydrate, which is carried away by the inert gas (e.g., nitrogen) circulated through the roller kiln. The second stage sintering is used for activating the precursor, promoting the nucleation of crystal grains, promoting the decomposition of a carbon source and enhancing the coating effect of the carbon layer. The third sintering function is to make the raw materials fully react and improve the crystallization degree of the crystal grains.
Therefore, the application selects the ferric phosphate precursor ferric phosphate dihydrate as the main iron source, omits the precursor preparation step, reduces the industrial cost, adds the proper iron source doping agent, does not introduce new impurities, improves the electrical property of the material, refines the crystal grains by adopting the sectional sintering process, and further improves the comprehensive property of the lithium iron phosphate material. The method is simple to operate, easy to implement and convenient for large-scale production, can directly improve production on the basis of the existing ferric phosphate process, and is suitable for large-scale popularization and use.
Preferably, the solvent is purified water.
Preferably, in the step S1, the molar ratio of total lithium, total iron and total phosphorus in the total raw materials is (1.00-1.20): (0.93-0.99): 1. Of the three raw materials, according to the chemical formula composition, lithium is slightly excessive, iron is opposite, the consumption is small, and the excessive lithium is firstly because lithium can volatilize at high temperature, and part of lithium cannot enter an ion lattice in an ionic state, so that capacity is lost; meanwhile, the lithium is used as a fluxing agent, and the proper excessive amount can inhibit particle overburning, thereby being beneficial to the removal/intercalation of lithium ions in the battery. The main function of the small amount of iron is to generate iron vacancies in crystal lattice so as to reduce the diffusion energy barrier of lithium ions, increase the transmission rate of lithium ions in a one-dimensional channel and improve the rate capability of the battery. It is worth noting that, if spray drying is adopted in the subsequent drying, and press filtration drying, oven ordinary drying and the like are adopted, more raw material lithium is lost, so that the generation amount of lithium iron phosphate is affected, the loss of the spray drying lithium is smaller, the spray drying preferably has the air inlet temperature of 180-250 ℃ and the air outlet temperature of 80-110 ℃.
Preferably, the lithium source is one or a combination of more selected from lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, lithium chloride, lithium dihydrogen phosphate and the like; the phosphorus source is one or more selected from phosphoric acid, ferric phosphate, lithium dihydrogen phosphate, diammonium hydrogen phosphate and the like.
Preferably, the carbon source is one or more selected from glucose, sucrose, fructose, polyethylene glycol, ascorbic acid, and the like.
Preferably, the iron source dopant in the step S1 is one or a combination of more iron-containing compounds selected from iron oxide red, iron oxide yellow, iron oxide black, ferric hydroxide, ferric carbonate and the like.
Preferably, the slurry D50 particle size is controlled to be 0.30-0.45 μm after sanding in the step S1.
Preferably, the total carbon source consumption in the step S1 accounts for 10-20% of the mass of the finished lithium iron phosphate, and the titanium dioxide consumption accounts for 1000-5000 ppm of the mass of the finished product.
Preferably, the three-stage heating rate of the high-temperature sectional calcination in the step S3 is respectively 1-5 ℃/min, 1-5 ℃/min and 3-15 ℃/min.
Preferably, the pulverizing mode in the step S3 is jet milling, and the particle diameter D50 after the milling is controlled to be 0.8-1.5 mu m. Lithium iron phosphate materials are required to have higher pole piece compacted densities in order to achieve higher energy densities (the material evaluation stage is reflected by the powder compacted density profile). As obtained from practical production experience, controlling the particle size distribution in this range (D50 of about 0.8-1.5 μm) helps to achieve higher compacted densities, and too small a particle size D50 results in a material with a compromised compacted density.
Example 1
(1) 5688.2G of ferric phosphate dihydrate, 1275.0g of lithium carbonate, 176.2g of sucrose, 454.4g of polyethylene glycol, 19.0g of titanium dioxide and 11.4g of ferric oxide red are respectively weighed and mixed in 12kg of pure water, and are coarsely ground in a coarse grinding machine until the average size D50 of the slurry is 1.9 mu m, and are finely ground in a fine grinding machine until the average size D50 of the slurry is 0.43 mu m. Wherein the molar ratio of the lithium element to the iron element to the phosphorus element is 1.01:0.97:1.
(2) And (3) spray-drying the slurry obtained in the step (1) at the air inlet temperature of 240 ℃ and the air outlet temperature of 90 ℃ to obtain the lithium iron phosphate precursor.
(3) And (3) placing the lithium iron phosphate precursor in a box-type atmosphere furnace, under the protection of a circulating nitrogen atmosphere, heating to 290 ℃ at a speed of 2 ℃/min for calcination for 3 hours, heating to 650 ℃ at a speed of 2 ℃/min for calcination for 2 hours, and heating to 760 ℃ at a speed of 10 ℃/min for calcination for 5 hours. After natural cooling, the powder was crushed to an average particle size D50 of 1.1 μm to obtain a lithium iron phosphate material, and the material was sampled for SEM and XRD analysis, and the results are shown in fig. 1 and 2. XRD patterns show that the synthesized material has sharp peak shape, good crystal growth and peak spectrum corresponding to lithium iron phosphate. SEM shows that the primary particles of the lithium iron phosphate material are in a similar spherical appearance, and the particle size is about 100-200 nm.
Example 2
(1) 4822.4G of ferric phosphate dihydrate, 1080.9g of lithium carbonate, 149.4g of sucrose, 385.2g of polyethylene glycol, 16.1g of titanium dioxide and 10.9g of iron oxide yellow are respectively weighed and mixed in 10kg of pure water, and are coarsely ground in a coarse grinding machine until the average size D50 of the slurry is 1.8 mu m, and are finely ground in a fine grinding machine until the average size D50 of the slurry is 0.42 mu m. Wherein the molar ratio of the lithium element to the iron element to the phosphorus element is 1.01:0.97:1.
(2) And (3) spray-drying the slurry obtained in the step (1) at the air inlet temperature of 240 ℃ and the air outlet temperature of 90 ℃ to obtain the lithium iron phosphate precursor.
(3) And (3) placing the lithium iron phosphate precursor in a box-type atmosphere furnace, under the protection of a circulating nitrogen atmosphere, heating to 290 ℃ at a speed of 2 ℃/min for calcination for 3 hours, heating to 650 ℃ at a speed of 2 ℃/min for calcination for 2 hours, and heating to 760 ℃ at a speed of 10 ℃/min for calcination for 5 hours. After natural cooling, crushing to an average particle size D50 of 1.0 mu m to obtain the lithium iron phosphate material.
Example 3
(1) 5341.2G of ferric phosphate dihydrate, 1206.2g of lithium carbonate, 167.2g of sucrose, 431.2g of polyethylene glycol, 18.7g of titanium dioxide and 15.8g of ferric oxide red are respectively weighed and mixed in 11kg of pure water, and are coarsely ground in a coarse grinding machine until the average size D50 of the slurry is 1.9 mu m, and are finely ground in a fine grinding machine until the average size D50 of the slurry is 0.42 mu m. Wherein the molar ratio of the lithium element to the iron element to the phosphorus element is 1.01:0.97:1.
(2) And (3) spray-drying the slurry obtained in the step (1) at the air inlet temperature of 240 ℃ and the air outlet temperature of 90 ℃ to obtain the lithium iron phosphate precursor.
(3) And (3) placing the lithium iron phosphate precursor in a box-type atmosphere furnace, under the protection of a circulating nitrogen atmosphere, heating to 270 ℃ at a speed of 2 ℃/min for calcination for 3 hours, heating to 680 ℃ at a speed of 2 ℃/min for calcination for 2 hours, and heating to 790 ℃ at a speed of 10 ℃/min for calcination for 5 hours. After natural cooling, crushing to an average particle size D50 of 1.2 mu m to obtain the lithium iron phosphate material.
Comparative example 1
This comparative example is compared to example 1, with the difference that no iron-containing dopant is added in step (1), and only two-stage sintering is performed in step (3), and the sintering method is specifically as follows: heating to 290 ℃ at the speed of 2 ℃/min, calcining at constant temperature for 3h, heating to 760 ℃ at the speed of 2 ℃/min, and calcining at constant temperature for 7h.
(1) 5688.2G of ferric phosphate dihydrate, 1275.0g of lithium carbonate, 176.2g of sucrose, 454.4g of polyethylene glycol and 19.0g of titanium dioxide are respectively weighed and mixed into 12kg of pure water, and are coarsely ground in a coarse grinding machine until the average size D50 of the slurry is 1.8 mu m, and then finely ground in a fine grinding machine until the average size D50 of the slurry is 0.40 mu m. Wherein the molar ratio of the lithium element to the iron element to the phosphorus element is 1.02:0.96:1.
(2) Spray drying the slurry obtained in the step (1) at an air inlet temperature of 240 ℃ and an air outlet temperature of 90 ℃ to obtain a lithium iron phosphate precursor;
(3) And (3) placing the lithium iron phosphate precursor in a box-type atmosphere furnace, calcining for 3 hours at 290 ℃ and then calcining for 7 hours at 760 ℃ under the protection of circulated nitrogen atmosphere. After natural cooling, crushing to an average particle size D50 of 1.1 mu m to obtain the lithium iron phosphate material.
The results of the performance test of the lithium iron phosphate samples obtained in examples 1 to 3 and comparative example 1 are shown in Table 1.
Table 1 comparison of lithium iron phosphate properties of examples
While preferred embodiments of the present invention have been described, additional variations and modifications in those embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. It is therefore intended that the following claims be interpreted as including the preferred embodiments and all such alterations and modifications as fall within the scope of the invention. It will be apparent to those skilled in the art that various modifications and variations can be made to the present invention without departing from the spirit or scope of the invention. Thus, it is intended that the present invention also include such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
Claims (7)
1. The method for preparing the high-performance lithium iron phosphate by sectional sintering is characterized by comprising the following steps of:
S1, mixing ferric phosphate dihydrate, a lithium source, a phosphorus source, a carbon source, titanium dioxide and an iron source doping agent in a solvent, and sanding the mixture to obtain slurry; the iron source doping agent accounts for 500-10000 ppm of the mass of the finished product; the iron source doping agent is one or a combination of more than one of iron oxide red, iron oxide yellow, iron oxide black, ferric hydroxide and ferric carbonate; the molar ratio of total lithium, total iron and total phosphorus in all raw materials is (1.00-1.20): (0.93 to 0.99): 1; the total consumption of the carbon source accounts for 10-20% of the mass of the finished lithium iron phosphate, and the consumption of the titanium dioxide accounts for 1000-5000 ppm of the mass of the finished product;
S2, drying the slurry to obtain a lithium iron phosphate precursor;
S3, carrying out high-temperature sectional calcination on the lithium iron phosphate precursor in an inert atmosphere, and then crushing to obtain a high-rate lithium iron phosphate anode material; the high-temperature sectional calcination process comprises the following steps:
preserving heat for 2-4 hours at 260-290 ℃;
preserving heat for 2-3 hours at 620-680 ℃;
and preserving heat for 5-7 hours at 720-800 ℃.
2. The method for preparing high-performance lithium iron phosphate by sectional sintering according to claim 1, wherein the method comprises the steps of,
The lithium source is one or a combination of more selected from lithium carbonate, lithium hydroxide, lithium phosphate, lithium nitrate, lithium chloride and lithium dihydrogen phosphate; the phosphorus source is one or a combination of more selected from phosphoric acid, ferric phosphate, lithium dihydrogen phosphate and diammonium hydrogen phosphate.
3. The method for preparing high-performance lithium iron phosphate by sectional sintering according to claim 1, wherein the method comprises the steps of,
The carbon source is one or a combination of more than one of glucose, sucrose, fructose, polyethylene glycol and ascorbic acid.
4. The method for preparing high-performance lithium iron phosphate by sectional sintering according to claim 1, wherein the method comprises the steps of,
And (3) controlling the grain size of the slurry D50 to be 0.30-0.45 mu m after the sand grinding in the step S1.
5. The method for preparing high-performance lithium iron phosphate by sectional sintering according to claim 1, wherein the method comprises the steps of,
And step S2, spray drying is adopted for drying, the air inlet temperature is 180-250 ℃, and the air outlet temperature is 80-110 ℃.
6. The method for preparing high-performance lithium iron phosphate by sectional sintering according to claim 1, wherein the method comprises the steps of,
And step S3, the three-stage heating rate of the high-temperature sectional calcination is respectively 1-5 ℃/min, 1-5 ℃/min and 3-15 ℃/min.
7. The method for preparing high-performance lithium iron phosphate by sectional sintering according to claim 1, wherein the method comprises the steps of,
And the crushing mode in the step S3 is air current crushing, and the particle size D50 after crushing is controlled to be 0.8-1.5 mu m.
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