CN117383535A - Preparation method of low-cost high-compaction lithium iron phosphate - Google Patents
Preparation method of low-cost high-compaction lithium iron phosphate Download PDFInfo
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- CN117383535A CN117383535A CN202311559394.XA CN202311559394A CN117383535A CN 117383535 A CN117383535 A CN 117383535A CN 202311559394 A CN202311559394 A CN 202311559394A CN 117383535 A CN117383535 A CN 117383535A
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- iron phosphate
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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 77
- 238000005056 compaction Methods 0.000 title claims abstract description 35
- 238000002360 preparation method Methods 0.000 title claims abstract description 32
- 239000000203 mixture Substances 0.000 claims abstract description 131
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 85
- 238000000498 ball milling Methods 0.000 claims abstract description 52
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 46
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 44
- 238000002156 mixing Methods 0.000 claims abstract description 39
- 238000005245 sintering Methods 0.000 claims abstract description 28
- 229910052742 iron Inorganic materials 0.000 claims abstract description 22
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 21
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 21
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 21
- 238000000034 method Methods 0.000 claims abstract description 21
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 21
- 239000011574 phosphorus Substances 0.000 claims abstract description 21
- 230000001590 oxidative effect Effects 0.000 claims abstract description 4
- 239000002243 precursor Substances 0.000 claims description 56
- 229910021389 graphene Inorganic materials 0.000 claims description 38
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 34
- 238000010438 heat treatment Methods 0.000 claims description 26
- 239000000463 material Substances 0.000 claims description 26
- 239000011259 mixed solution Substances 0.000 claims description 26
- 238000001035 drying Methods 0.000 claims description 25
- 239000002071 nanotube Substances 0.000 claims description 24
- 239000011858 nanopowder Substances 0.000 claims description 22
- 238000003756 stirring Methods 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 21
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical group CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 20
- 239000000843 powder Substances 0.000 claims description 20
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 14
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 14
- 230000008014 freezing Effects 0.000 claims description 14
- 238000007710 freezing Methods 0.000 claims description 14
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 14
- 239000002135 nanosheet Substances 0.000 claims description 13
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 12
- 239000002064 nanoplatelet Substances 0.000 claims description 11
- 238000000227 grinding Methods 0.000 claims description 10
- 239000006012 monoammonium phosphate Substances 0.000 claims description 10
- 238000004140 cleaning Methods 0.000 claims description 9
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 9
- 239000002244 precipitate Substances 0.000 claims description 9
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims description 8
- 229940062993 ferrous oxalate Drugs 0.000 claims description 8
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 8
- 239000011790 ferrous sulphate Substances 0.000 claims description 8
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims description 8
- OWZIYWAUNZMLRT-UHFFFAOYSA-L iron(2+);oxalate Chemical compound [Fe+2].[O-]C(=O)C([O-])=O OWZIYWAUNZMLRT-UHFFFAOYSA-L 0.000 claims description 8
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 8
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 8
- 239000005955 Ferric phosphate Substances 0.000 claims description 7
- 239000006185 dispersion Substances 0.000 claims description 7
- 229940032958 ferric phosphate Drugs 0.000 claims description 7
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 7
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 6
- 239000007788 liquid Substances 0.000 claims description 6
- 239000000243 solution Substances 0.000 claims description 6
- MCDLETWIOVSGJT-UHFFFAOYSA-N acetic acid;iron Chemical compound [Fe].CC(O)=O.CC(O)=O MCDLETWIOVSGJT-UHFFFAOYSA-N 0.000 claims description 5
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims description 4
- 238000001291 vacuum drying Methods 0.000 claims description 4
- NWZSZGALRFJKBT-KNIFDHDWSA-N (2s)-2,6-diaminohexanoic acid;(2s)-2-hydroxybutanedioic acid Chemical compound OC(=O)[C@@H](O)CC(O)=O.NCCCC[C@H](N)C(O)=O NWZSZGALRFJKBT-KNIFDHDWSA-N 0.000 claims description 3
- SECXISVLQFMRJM-UHFFFAOYSA-N N-Methylpyrrolidone Chemical compound CN1CCCC1=O SECXISVLQFMRJM-UHFFFAOYSA-N 0.000 claims description 3
- 239000011324 bead Substances 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
- JEIPFZHSYJVQDO-UHFFFAOYSA-N ferric oxide Chemical compound O=[Fe]O[Fe]=O JEIPFZHSYJVQDO-UHFFFAOYSA-N 0.000 claims description 3
- 229960005191 ferric oxide Drugs 0.000 claims description 3
- IKDUDTNKRLTJSI-UHFFFAOYSA-N hydrazine monohydrate Substances O.NN IKDUDTNKRLTJSI-UHFFFAOYSA-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
- UONOETXJSWQNOL-UHFFFAOYSA-N tungsten carbide Chemical compound [W+]#[C-] UONOETXJSWQNOL-UHFFFAOYSA-N 0.000 claims description 3
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 3
- 239000007787 solid Substances 0.000 claims 1
- 238000012360 testing method Methods 0.000 description 6
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 229910052782 aluminium Inorganic materials 0.000 description 3
- 238000004519 manufacturing process Methods 0.000 description 3
- 239000007791 liquid phase Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 239000007790 solid phase Substances 0.000 description 2
- 238000010532 solid phase synthesis reaction Methods 0.000 description 2
- 239000010405 anode material Substances 0.000 description 1
- 239000006229 carbon black Substances 0.000 description 1
- 239000002041 carbon nanotube Substances 0.000 description 1
- 229910021393 carbon nanotube Inorganic materials 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 238000009831 deintercalation Methods 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 239000007772 electrode material Substances 0.000 description 1
- 229910001385 heavy metal Inorganic materials 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 238000009776 industrial production Methods 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
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- 238000009768 microwave sintering Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000007774 positive electrode material Substances 0.000 description 1
- 238000007670 refining Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
Classifications
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
- C01B25/00—Phosphorus; Compounds thereof
- C01B25/16—Oxyacids of phosphorus; Salts thereof
- C01B25/26—Phosphates
- C01B25/45—Phosphates containing plural metal, or metal and ammonium
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/11—Powder tap density
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2006/00—Physical properties of inorganic compounds
- C01P2006/40—Electric properties
-
- 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
Abstract
The invention discloses a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following steps: s100: mixing an iron source and a phosphorus source, and oxidizing to obtain a first mixture; s200: ball milling, mixing and sintering the first mixture, a lithium source and a carbon source to obtain high-compaction lithium iron phosphate; the ratio of the amounts of iron, phosphorus and lithium in the iron source, phosphorus source and lithium source is (0.95-1.15): (1-1.25): (1-1.0.2). The lithium iron phosphate prepared by the method has higher compaction density, and can effectively improve the capacity of the battery.
Description
Technical Field
The invention relates to the technical field of lithium iron phosphate preparation, in particular to a preparation method of low-cost high-compaction lithium iron phosphate.
Background
The lithium iron phosphate is a lithium ion battery electrode material and is mainly used for various lithium ion batteries. The lithium iron phosphate does not contain any heavy metal elements harmful to human bodies, and is the safest lithium ion battery anode material. The lithium iron phosphate has good lattice stability, and the influence of lithium ion intercalation and deintercalation on the lattice is small, so the lithium iron phosphate has good reversibility, so the lithium iron phosphate battery has good charge and discharge performance and service life, and the lithium iron phosphate battery can adapt to high-power charging, and the charging efficiency is improved.
In the practical application process of the lithium iron phosphate battery, the problems of low bulk density, low electron conductivity, low ion diffusion coefficient, low tap density, low capacity density and the like still exist. The reasons for these disadvantages of lithium iron phosphate batteries are related to the preparation method of lithium iron phosphate in addition to the limitation of the performance of lithium iron phosphate itself. Currently, there are various methods for preparing lithium iron phosphate, and they can be broadly classified into a liquid phase method and a solid phase method. The liquid phase method comprises a coprecipitation method, a hydrothermal method, a sol-gel method and other low-temperature synthesis methods, the solid phase method comprises a high-temperature solid phase sintering method, a carbothermic reduction method, a microwave sintering method and the like, and the most widely used high-temperature solid phase sintering method in the actual industrial production of lithium iron phosphate. However, the lithium iron phosphate prepared by the existing preparation method of the lithium iron phosphate still has the problems of low compaction density, small capacity and the like.
Disclosure of Invention
The invention provides a preparation method of low-cost high-compaction lithium iron phosphate, and the lithium iron phosphate prepared by the method has higher compaction density and can effectively improve the capacity of a battery.
The technical scheme adopted for solving the technical problems is as follows: a method for preparing low cost, high compaction lithium iron phosphate comprising:
s100: mixing an iron source and a phosphorus source, and oxidizing to obtain a first mixture;
s200: ball milling, mixing and sintering the first mixture, a lithium source and a carbon source to obtain high-compaction lithium iron phosphate;
wherein the iron source is selected from at least one of ferrous sulfate, ferrous oxalate, ferrous acetate, ferrous oxalate, ferric oxide red and ferric phosphate, the phosphorus source is selected from at least one of phosphoric acid, monoammonium phosphate, ferric phosphate, ammonium hydrogen phosphate and monoammonium phosphate, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide and lithium dihydrogen phosphate, and the carbon source comprises the following components in parts by mass: (0.5-0.78) porous graphene nanoplatelets and doped nanotubes.
Further, the ratio of the amounts of iron, phosphorus, and lithium in the iron source, phosphorus source, and lithium source is (0.95-1.15): (1-1.25): (1-1.0.2).
Further, S100 specifically includes the following steps:
s110: mixing an iron source and a phosphorus source to obtain a nano powder mixture;
s120: mixing the nano powder mixture with water, and stirring at 550-650 rpm for 40-50 min to obtain a first mixed solution;
s130: dropwise adding the first mixed solution into hydrogen peroxide at the temperature of 40-48 ℃, then standing for 10-15 h in a temperature environment at the temperature of 70-78 ℃, then placing into a freezing chamber and drying in vacuum for 20-25 h to obtain a first mixture.
Further, in S130, the first mixed solution is dripped into the hydrogen peroxide in ultrasonic vibration at a speed of 4mL/min-6 mL/min.
Further, S200 specifically includes the following steps:
s210: adding the first mixture and a lithium source into a ball mill, performing wet ball milling for 10-15 h, and drying to obtain a precursor mixture;
s220: sintering the precursor mixture for 5-7 h at the temperature of 650-750 ℃ and controlling the heating rate of the precursor mixture to be 2-4 ℃/min to obtain the lithium iron phosphate precursor.
Further, in S210, the ball-to-material ratio is controlled at (19-21): (1-1.1), ball milling rotating speed is 150-250 r/min, and the ball milling medium is ethanol.
Further, S200 further includes the following steps:
s230: grinding the lithium iron phosphate precursor into powder with the diameter of 20-50 nm, and adding a carbon source into the powder to obtain a carbon-containing mixture;
s240: sintering the carbon-containing mixture for 8-12 h at the temperature of 700-880 ℃, and controlling the heating rate of the carbon-containing mixture to be 1-1.2 ℃/min to obtain the high-compaction lithium iron phosphate.
Further, the porous graphene nanoplatelets are prepared by the following steps:
s410: mixing graphene oxide with water, and stirring at a speed of 150-250 r/min for 5-7 h at a temperature of 0-4 ℃ to obtain graphene oxide liquid;
s420: heating the graphene oxide liquid to 50-60 ℃, then dropwise adding hydrogen peroxide while stirring, heating to 85-95 ℃ after the dropwise adding is completed, and continuously stirring for 1-2 h to obtain a crude graphene material;
s430: and centrifuging the crude graphene material at the rotating speed of 8000-9000 rpm, and taking, cleaning and drying the precipitate to obtain the porous graphene nano-sheet.
Further, the doped nanotubes are prepared by the steps of:
s510: ball-milling and mixing aluminum powder and PEI solution, wherein the ball-milling time is controlled to be 10-15 h, and the ball-material ratio is controlled to be (10-15): (1-1.1), ball milling rotating speed is 250-350 r/min, and tungsten carbide with diameter of 0.2-0.5 mm is selected as ball milling beads to obtain a first mixture;
s520: mixing the first mixture with water, centrifuging at 2000-300 rpm for 2-5 h, cleaning the precipitate, and drying to obtain a second mixture;
s530: adding the second mixture into hydrazine hydrate, stirring for 20-30 min, standing for 20-25 h, adding water, freezing, and vacuum drying to obtain the doped nanotube.
Further, the carbon source is prepared by the following steps:
s610: adding the porous graphene nano-sheets and the doped nano-tubes into an N-methylpyrrolidone solution, and then performing ultrasonic dispersion for 5-7 hours to obtain a dispersion material;
s620: centrifuging the dispersion material for 3-5 h at 5500-6500 rpm, collecting precipitate, cleaning, and drying to obtain carbon source.
Compared with the prior art, the invention has the advantages that: through refining the lithium iron phosphate precursor and matching the porous graphene nano sheet and the doped nano tube, the more fine and uniform lithium iron phosphate can be prepared, so that the compaction density of the lithium iron phosphate is effectively improved, and the capacity of a lithium iron phosphate battery is improved.
Detailed Description
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of embodiments of the invention will be rendered by reference to specific embodiments thereof which are illustrated in the appended drawings.
The embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following steps:
s100: mixing an iron source and a phosphorus source, and oxidizing to obtain a first mixture;
s200: and ball-milling, mixing and sintering the first mixture, the lithium source and the carbon source to obtain the high-compaction lithium iron phosphate.
Wherein the ratio of the amounts of iron, phosphorus and lithium in the iron source, phosphorus source and lithium source is (0.95-1.15): (1-1.25): (1-1.0.2).
Wherein, the main function of S100 is to uniformly mix the iron source and the phosphorus source and oxidize to obtain ferric phosphate. S100 specifically comprises the following steps:
s110: mixing an iron source and a phosphorus source to obtain a nano powder mixture;
s120: mixing the nano powder mixture with water, and stirring at 550-650 rpm for 40-50 min to obtain a first mixed solution;
s130: dropwise adding the first mixed solution into hydrogen peroxide at the temperature of 40-48 ℃, then standing for 10-15 h in a temperature environment at the temperature of 70-78 ℃, then placing into a freezing chamber and drying in vacuum for 20-25 h to obtain a first mixture.
In S120, the nano powder mixture is dispersed in water as much as possible, so that the fine iron phosphate material is obtained in the subsequent preparation. S130 is mainly to oxidize the mixture, and in S130, the first mixed solution is dripped into the ultrasonically vibrated hydrogen peroxide at a speed of 4mL/min-6mL/min, so that thorough oxidation and mixing can be performed.
Preferably, the nano-powder mixture is mixed with water in S120 and stirred at 600rpm for 45min to obtain a first mixed solution.
Preferably, in S130, the first mixed solution is added dropwise to hydrogen peroxide at 42 ℃, then placed in a temperature environment at 75 ℃ for 12 hours, and then placed in a freezing chamber and dried in vacuum for 22 hours to obtain the first mixture.
The iron source is at least one selected from ferrous sulfate, ferrous oxalate, ferrous acetate, ferrous oxalate, ferric oxide red and ferric phosphate, and the phosphorus source is at least one selected from phosphoric acid, monoammonium phosphate, ferric phosphate, ammonium hydrogen phosphate and monoammonium phosphate.
Preferably, the iron source is ferrous sulfate and the phosphorus source is monoammonium phosphate.
Preferably, the iron source is ferrous acetate and the phosphorus source is monoammonium phosphate.
Wherein, S200 specifically includes the following steps:
s210: adding the first mixture and a lithium source into a ball mill, performing wet ball milling for 10-15 h, and drying to obtain a precursor mixture;
s220: sintering the precursor mixture for 5-7 h at the temperature of 650-750 ℃ and controlling the heating rate of the precursor mixture to be 2-4 ℃/min to obtain the lithium iron phosphate precursor.
The step S210 is mainly used for mixing the first mixture and the lithium source, and in the step S210, the ball-to-material ratio is controlled in (19-21): (1-1.1), ball milling rotating speed is 150-250 r/min, and the ball milling medium is ethanol. The lithium source is at least one selected from lithium carbonate, lithium hydroxide and lithium dihydrogen phosphate. Preferably, the lithium source is lithium dihydrogen phosphate. In the step S220, the precursor is mainly sintered, and since the particles of the precursor are very fine, the temperature rising rate of the precursor mixture needs to be noted in the sintering process, so as to prevent the occurrence of the over-sintering problem.
Wherein, S200 further comprises the following steps:
s230: grinding the lithium iron phosphate precursor into powder with the diameter of 20-50 nm, and adding a carbon source into the powder to obtain a carbon-containing mixture;
s240: sintering the carbon-containing mixture for 8-12 h at the temperature of 700-880 ℃, and controlling the heating rate of the carbon-containing mixture to be 1-1.2 ℃/min to obtain the high-compaction lithium iron phosphate.
The carbon source comprises the following components in parts by mass (1-1.12): (0.5-0.78) porous graphene nanoplatelets and doped nanotubes. Preferably, the mass ratio of the porous graphene nanoplatelets to the doped nanotubes is 1.05:0.62.
wherein, the carbon source in S230 is prepared by the following method:
s610: adding the porous graphene nano-sheets and the doped nano-tubes into an N-methylpyrrolidone solution, and then performing ultrasonic dispersion for 5-7 hours to obtain a dispersion material;
s620: centrifuging the dispersion material for 3-5 h at 5500-6500 rpm, collecting precipitate, cleaning, and drying to obtain carbon source.
Through steps such as dispersion, off-line, on the one hand, the porous graphene nano-sheets and the doped nano-tubes can be uniformly mixed, and on the other hand, magazines in the preparation process of the porous graphene nano-sheets and the doped nano-tubes can be removed, so that the preparation of lithium iron phosphate is not influenced.
By using the porous graphene nano-sheet, the lithium iron phosphate precursor can be well distributed on the surface of the nano-sheet, so that the size of lithium iron phosphate particles is effectively reduced. In order to facilitate understanding and manufacturing, the present application provides a manufacturing step of a porous graphene nanosheet, and a specific preparation method is as follows:
s410: mixing graphene oxide with water, and stirring at a speed of 150-250 r/min for 5-7 h at a temperature of 0-4 ℃ to obtain graphene oxide liquid;
s420: heating the graphene oxide liquid to 50-60 ℃, then dropwise adding hydrogen peroxide while stirring, heating to 85-95 ℃ after the dropwise adding is completed, and continuously stirring for 1-2 h to obtain a crude graphene material;
s430: and centrifuging the crude graphene material at the rotating speed of 8000-9000 rpm, and taking, cleaning and drying the precipitate to obtain the porous graphene nano-sheet.
The aluminum doped nano tube is used, wherein aluminum is uniformly distributed on the surface of the nano tube, so that the contact area of aluminum and a precursor can be enlarged, lattice distortion is guided, iron can be effectively prevented from being oxidized in the carbon nano tube atmosphere, and the performances of conductivity, capacity and the like of lithium iron phosphate are improved. In order to facilitate understanding and manufacturing, the present application further provides a preparation method of the doped nanotube:
s510: ball-milling and mixing aluminum powder and PE I solution, wherein the ball-milling time is controlled to be 10-15 h, and the ball-material ratio is controlled to be (10-15): (1-1.1), ball milling rotating speed is 250-350 r/min, and tungsten carbide with diameter of 0.2-0.5 mm is selected as ball milling beads to obtain a first mixture;
s520: mixing the first mixture with water, centrifuging at 2000-300 rpm for 2-5 h, cleaning the precipitate, and drying to obtain a second mixture;
s530: adding the second mixture into hydrazine hydrate, stirring for 20-30 min, standing for 20-25 h, adding water, freezing, and vacuum drying to obtain the doped nanotube.
Example 1:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous sulfate and ammonium dihydrogen phosphate to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring at 600rpm for 45min to obtain a first mixed solution; dropwise adding the first mixed solution into hydrogen peroxide at 42 ℃, then standing for 12 hours in a temperature environment at 75 ℃, then placing into a freezing chamber and drying in vacuum for 22 hours to obtain a first mixture;
s200: adding the first mixture and lithium dihydrogen phosphate into a ball mill, performing wet ball milling for 12 hours, wherein the ball-to-material ratio of the wet ball milling is controlled at 20:1.05, ball milling rotating speed is 200r/min, ball milling medium is ethanol, and then drying is carried out to obtain a precursor mixture; sintering the precursor mixture for 6 hours at the temperature of 700 ℃, and controlling the heating rate of the precursor mixture to be 3 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 40nm, and adding the powder with the mass part ratio of 1.05:0.62 porous graphene nanoplatelets and doped nanotubes to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 10 hours at the temperature of 850 ℃, and controlling the heating rate of the carbon-containing mixture to be 1.1 ℃/min to obtain the high-compaction lithium iron phosphate.
Example 2:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous acetate and monoammonium phosphate to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring at 580rpm for 40min to obtain a first mixed solution; dropwise adding the first mixed solution into hydrogen peroxide at 42 ℃, then standing for 11 hours in a temperature environment at 70 ℃, then placing into a freezing chamber and drying in vacuum for 25 hours to obtain a first mixture;
s200: adding the first mixture and lithium dihydrogen phosphate into a ball mill, performing wet ball milling for 10 hours, wherein the ball-to-material ratio of the wet ball milling is controlled at 20:1. the ball milling rotating speed is 230r/min, the ball milling medium is ethanol, and then the mixture is dried to obtain a precursor mixture; sintering the precursor mixture for 7 hours at 680 ℃ and controlling the heating rate of the precursor mixture to be 3.5 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 50nm, and adding the powder with the mass part ratio of 1.05:0.62 porous graphene nanoplatelets and doped nanotubes to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 12 hours at the temperature of 880 ℃, and controlling the heating rate of the carbon-containing mixture to be 1 ℃/min to obtain the high-compaction lithium iron phosphate.
Example 3:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous oxalate and phosphoric acid to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring for 50min at 550rpm to obtain a first mixed solution; dropwise adding the first mixed solution into hydrogen peroxide at 48 ℃, then standing for 10 hours in a temperature environment at 78 ℃, then placing into a freezing chamber and drying in vacuum for 20 hours to obtain a first mixture;
s200: adding the first mixture and lithium hydroxide into a ball mill, performing wet ball milling for 15 hours, wherein the ball-material ratio of the wet ball milling is controlled at 19: 1. the ball milling rotating speed is 180r/min, the ball milling medium is ethanol, and then the mixture is dried to obtain a precursor mixture; sintering the precursor mixture for 5 hours at the temperature of 720 ℃, and controlling the heating rate of the precursor mixture to be 2 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 30nm, and adding the powder with the mass part ratio of 1.05:0.62 porous graphene nanoplatelets and doped nanotubes to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 9 hours at the temperature of 830 ℃, and controlling the heating rate of the carbon-containing mixture to be 1.2 ℃/min to obtain the high-compaction lithium iron phosphate.
Example 4:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous oxalate and monoammonium phosphate to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring for 48min at a rotation speed of 620rpm to obtain a first mixed solution; dropwise adding the first mixed solution into 40 ℃ hydrogen peroxide, standing for 14 hours in a temperature environment of 76 ℃, and then placing the mixture into a freezing chamber and vacuum drying for 23 hours to obtain a first mixture;
s200: adding the first mixture and a lithium source into a ball mill, performing wet ball milling for 14h, wherein the ball-material ratio is controlled at 21: 1. the ball milling rotating speed is 150r/min, the ball milling medium is ethanol, and then the mixture is dried to obtain a precursor mixture; sintering the precursor mixture for 5.5 hours at the temperature of 650 ℃, and controlling the heating rate of the precursor mixture to be 2.8 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 50nm, and adding the powder with the mass part ratio of 1.05:0.62 porous graphene nanoplatelets and doped nanotubes to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 8 hours at the temperature of 780 ℃, and controlling the heating rate of the carbon-containing mixture to be 1.15 ℃/min to obtain the high-compaction lithium iron phosphate.
Example 5:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous sulfate and ammonium dihydrogen phosphate to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring at 600rpm for 45min to obtain a first mixed solution; dropwise adding the first mixed solution into hydrogen peroxide at 42 ℃, then standing for 12 hours in a temperature environment at 75 ℃, then placing into a freezing chamber and drying in vacuum for 22 hours to obtain a first mixture;
s200: adding the first mixture and lithium dihydrogen phosphate into a ball mill, performing wet ball milling for 12 hours, wherein the ball-to-material ratio of the wet ball milling is controlled at 20:1.05, ball milling rotating speed is 200r/min, ball milling medium is ethanol, and then drying is carried out to obtain a precursor mixture; sintering the precursor mixture for 6 hours at the temperature of 700 ℃, and controlling the heating rate of the precursor mixture to be 3 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 40nm, and adding porous graphene nano sheets into the powder to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 10 hours at the temperature of 850 ℃, and controlling the heating rate of the carbon-containing mixture to be 1.1 ℃/min to obtain the high-compaction lithium iron phosphate.
Example 6:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous sulfate and ammonium dihydrogen phosphate to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring at 600rpm for 45min to obtain a first mixed solution; dropwise adding the first mixed solution into hydrogen peroxide at 42 ℃, then standing for 12 hours in a temperature environment at 75 ℃, then placing into a freezing chamber and drying in vacuum for 22 hours to obtain a first mixture;
s200: adding the first mixture and lithium dihydrogen phosphate into a ball mill, performing wet ball milling for 12 hours, wherein the ball-to-material ratio of the wet ball milling is controlled at 20:1.05, ball milling rotating speed is 200r/min, ball milling medium is ethanol, and then drying is carried out to obtain a precursor mixture; sintering the precursor mixture for 6 hours at the temperature of 700 ℃, and controlling the heating rate of the precursor mixture to be 3 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 40nm, and adding doped nanotubes into the powder to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 10 hours at the temperature of 850 ℃, and controlling the heating rate of the carbon-containing mixture to be 1.1 ℃/min to obtain the high-compaction lithium iron phosphate.
Example 7:
the embodiment provides a preparation method of low-cost high-compaction lithium iron phosphate, which comprises the following specific preparation steps:
s100: mixing ferrous sulfate and ammonium dihydrogen phosphate to obtain a nano powder mixture; mixing the nano powder mixture with water, and stirring at 600rpm for 45min to obtain a first mixed solution; dropwise adding the first mixed solution into hydrogen peroxide at 42 ℃, then standing for 12 hours in a temperature environment at 75 ℃, then placing into a freezing chamber and drying in vacuum for 22 hours to obtain a first mixture;
s200: adding the first mixture and lithium dihydrogen phosphate into a ball mill, performing wet ball milling for 12 hours, wherein the ball-to-material ratio of the wet ball milling is controlled at 20:1.05, ball milling rotating speed is 200r/min, ball milling medium is ethanol, and then drying is carried out to obtain a precursor mixture; sintering the precursor mixture for 6 hours at the temperature of 700 ℃, and controlling the heating rate of the precursor mixture to be 3 ℃/min to obtain a lithium iron phosphate precursor; grinding a lithium iron phosphate precursor into powder with the diameter of 40nm, and adding carbon black into the powder to obtain a carbon-containing mixture; sintering the carbon-containing mixture for 10 hours at the temperature of 850 ℃, and controlling the heating rate of the carbon-containing mixture to be 1.1 ℃/min to obtain the high-compaction lithium iron phosphate.
Performance testing
The high compaction lithium iron phosphate of examples 1-7 was subjected to a compaction density test and a capacity test, the test results being shown in table 1.
From the test results of examples 1-4, it can be seen that the lithium iron phosphate positive electrode material prepared by the preparation method provided by the invention has better compaction density and capacity; from the test results of examples 4-7, it can be seen that lithium iron phosphate with added porous graphene nanoplatelets and doped nanotubes has better compacted density and capacity.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be made by one skilled in the art without departing from the spirit and scope of the invention, and the scope of the invention should be assessed accordingly to that of the appended claims.
Claims (10)
1. A method for preparing low-cost and high-compaction lithium iron phosphate, which is characterized by comprising the following steps:
s100: mixing an iron source and a phosphorus source, and oxidizing to obtain a first mixture;
s200: ball milling, mixing and sintering the first mixture, a lithium source and a carbon source to obtain high-compaction lithium iron phosphate;
wherein the iron source is selected from at least one of ferrous sulfate, ferrous oxalate, ferrous acetate, ferrous oxalate, ferric oxide red and ferric phosphate, the phosphorus source is selected from at least one of phosphoric acid, monoammonium phosphate, ferric phosphate, ammonium hydrogen phosphate and monoammonium phosphate, the lithium source is selected from at least one of lithium carbonate, lithium hydroxide and lithium dihydrogen phosphate, and the carbon source comprises the following components in parts by mass: (0.5-0.78) porous graphene nanoplatelets and doped nanotubes.
2. The method of claim 1, wherein the ratio of the amounts of iron, phosphorus, and lithium species in the iron source, the phosphorus source, and the lithium source is (0.95-1.15): (1-1.25): (1-1.0.2).
3. The preparation method according to claim 1, wherein the step S100 specifically comprises the steps of:
s110: mixing the iron source and the phosphorus source to obtain a nano powder mixture;
s120: mixing the nano powder mixture with water, and stirring at a rotation speed of 550-650 rpm for 40-50 min to obtain a first mixed solution;
s130: and (3) dropwise adding the first mixed solution into hydrogen peroxide at the temperature of 40-48 ℃, standing for 10-15 h in a temperature environment at the temperature of 70-78 ℃, and then placing the first mixed solution into a freezing chamber and drying in vacuum for 20-25 h to obtain the first mixture.
4. The method according to claim 3, wherein in S130, the first mixed solution is dropped into the ultrasonically vibrated hydrogen peroxide at a rate of 4mL/min to 6 mL/min.
5. The preparation method according to claim 1, wherein the step S200 specifically comprises the steps of:
s210: adding the first mixture and the lithium source into a ball mill, performing wet ball milling for 10-15 hours, and drying to obtain a precursor mixture;
s220: sintering the precursor mixture for 5-7 h at the temperature of 650-750 ℃ and controlling the heating rate of the precursor mixture to be 2-4 ℃/min to obtain the lithium iron phosphate precursor.
6. The method of claim 5, wherein in S210, the ball-to-material ratio of the wet ball mill is controlled to be (19-21): (1-1.1), ball milling rotating speed is 150-250 r/min, and the ball milling medium is ethanol.
7. The method of claim 5, wherein S200 further comprises the steps of:
s230: grinding the lithium iron phosphate precursor into powder with the diameter of 20-50 nm, and adding the carbon source into the powder to obtain a carbon-containing mixture;
s240: sintering the carbon-containing mixture for 8-12 h at the temperature of 700-880 ℃, and controlling the heating rate of the carbon-containing mixture to be 1-1.2 ℃/min to obtain the high-pressure solid lithium iron phosphate.
8. The preparation method of claim 1, wherein the porous graphene nanoplatelets are prepared by the steps of:
s410: mixing graphene oxide with water, and stirring at a speed of 150-250 r/min for 5-7 h at a temperature of 0-4 ℃ to obtain graphene oxide liquid;
s420: heating the graphene oxide liquid to 50-60 ℃, then dropwise adding hydrogen peroxide while stirring, heating to 85-95 ℃ after the dropwise adding is completed, and continuously stirring for 1-2 h to obtain a crude graphene material;
s430: and centrifuging the crude graphene material at a rotating speed of 8000-9000 rpm, taking the precipitate, cleaning, and drying to obtain the porous graphene nanosheets.
9. The method of claim 1, wherein the doped nanotubes are prepared by:
s510: ball-milling and mixing aluminum powder and PEI solution, wherein the ball-milling time is controlled to be 10-15 h, and the ball-material ratio is controlled to be (10-15): (1-1.1), ball milling rotating speed is 250-350 r/min, and tungsten carbide with diameter of 0.2-0.5 mm is selected as ball milling beads to obtain a first mixture;
s520: mixing the first mixture with water, centrifuging at 2000-300 rpm for 2-5 h, taking the precipitate, cleaning, and drying to obtain a second mixture;
s530: and adding the second mixture into hydrazine hydrate, stirring for 20-30 min, standing for 20-25 h, adding water, freezing, and vacuum drying to obtain the doped nanotube.
10. The method of claim 1, wherein the carbon source is prepared by:
s610: adding the porous graphene nano-sheets and the doped nano-tubes into an N-methylpyrrolidone solution, and then performing ultrasonic dispersion for 5-7 hours to obtain a dispersion material;
s620: and centrifuging the dispersion material for 3-5 hours at the rotating speed of 5500-6500 rpm, taking the precipitate, cleaning and drying to obtain the carbon source.
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