CN117423811A - Lithium iron phosphate positive electrode material, and preparation method and application thereof - Google Patents
Lithium iron phosphate positive electrode material, and preparation method and application thereof Download PDFInfo
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- CN117423811A CN117423811A CN202311303157.7A CN202311303157A CN117423811A CN 117423811 A CN117423811 A CN 117423811A CN 202311303157 A CN202311303157 A CN 202311303157A CN 117423811 A CN117423811 A CN 117423811A
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- lithium iron
- iron phosphate
- positive electrode
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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
- 239000007774 positive electrode material Substances 0.000 title claims abstract description 58
- 238000002360 preparation method Methods 0.000 title abstract description 26
- 238000003756 stirring Methods 0.000 claims abstract description 58
- 229910052751 metal Inorganic materials 0.000 claims abstract description 53
- 239000002184 metal Substances 0.000 claims abstract description 53
- 239000005955 Ferric phosphate Substances 0.000 claims abstract description 50
- 229940032958 ferric phosphate Drugs 0.000 claims abstract description 50
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims abstract description 50
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 43
- 239000000243 solution Substances 0.000 claims abstract description 35
- 239000012266 salt solution Substances 0.000 claims abstract description 31
- 229920001940 conductive polymer Polymers 0.000 claims abstract description 27
- -1 hydroxyl ferric phosphate Chemical compound 0.000 claims abstract description 27
- 238000005406 washing Methods 0.000 claims abstract description 25
- NBIIXXVUZAFLBC-UHFFFAOYSA-N Phosphoric acid Chemical compound OP(O)(O)=O NBIIXXVUZAFLBC-UHFFFAOYSA-N 0.000 claims abstract description 20
- 239000010405 anode material Substances 0.000 claims abstract description 19
- 238000001035 drying Methods 0.000 claims abstract description 19
- 229910052742 iron Inorganic materials 0.000 claims abstract description 19
- 239000007788 liquid Substances 0.000 claims abstract description 18
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 18
- 239000000178 monomer Substances 0.000 claims abstract description 17
- 239000002244 precipitate Substances 0.000 claims abstract description 17
- 239000003999 initiator Substances 0.000 claims abstract description 16
- 230000001590 oxidative effect Effects 0.000 claims abstract description 16
- 238000010438 heat treatment Methods 0.000 claims abstract description 15
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims abstract description 13
- 235000011114 ammonium hydroxide Nutrition 0.000 claims abstract description 13
- 229910000147 aluminium phosphate Inorganic materials 0.000 claims abstract description 10
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims abstract description 10
- 238000001816 cooling Methods 0.000 claims abstract description 10
- GVGUFUZHNYFZLC-UHFFFAOYSA-N dodecyl benzenesulfonate;sodium Chemical compound [Na].CCCCCCCCCCCCOS(=O)(=O)C1=CC=CC=C1 GVGUFUZHNYFZLC-UHFFFAOYSA-N 0.000 claims abstract description 10
- 238000001914 filtration Methods 0.000 claims abstract description 10
- 235000019837 monoammonium phosphate Nutrition 0.000 claims abstract description 10
- 229940080264 sodium dodecylbenzenesulfonate Drugs 0.000 claims abstract description 10
- 239000012792 core layer Substances 0.000 claims abstract description 8
- 239000011247 coating layer Substances 0.000 claims abstract description 7
- 239000007800 oxidant agent Substances 0.000 claims abstract description 7
- 229920006395 saturated elastomer Polymers 0.000 claims abstract description 7
- 238000002156 mixing Methods 0.000 claims abstract description 6
- 239000000126 substance Substances 0.000 claims abstract description 6
- 238000000034 method Methods 0.000 claims description 24
- 235000003891 ferrous sulphate Nutrition 0.000 claims description 23
- 239000011790 ferrous sulphate Substances 0.000 claims description 23
- 229910000359 iron(II) sulfate Inorganic materials 0.000 claims description 23
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical group OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 18
- 239000011259 mixed solution Substances 0.000 claims description 18
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical group CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 17
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 claims description 15
- 229910001416 lithium ion Inorganic materials 0.000 claims description 15
- HSFWRNGVRCDJHI-UHFFFAOYSA-N alpha-acetylene Natural products C#C HSFWRNGVRCDJHI-UHFFFAOYSA-N 0.000 claims description 14
- 239000010936 titanium Substances 0.000 claims description 12
- OZAIFHULBGXAKX-UHFFFAOYSA-N 2-(2-cyanopropan-2-yldiazenyl)-2-methylpropanenitrile Chemical compound N#CC(C)(C)N=NC(C)(C)C#N OZAIFHULBGXAKX-UHFFFAOYSA-N 0.000 claims description 10
- PXHVJJICTQNCMI-UHFFFAOYSA-N Nickel Chemical compound [Ni] PXHVJJICTQNCMI-UHFFFAOYSA-N 0.000 claims description 9
- RTAQQCXQSZGOHL-UHFFFAOYSA-N Titanium Chemical compound [Ti] RTAQQCXQSZGOHL-UHFFFAOYSA-N 0.000 claims description 9
- 239000000376 reactant Substances 0.000 claims description 9
- 238000007789 sealing Methods 0.000 claims description 9
- 229910052719 titanium Inorganic materials 0.000 claims description 9
- 125000002534 ethynyl group Chemical group [H]C#C* 0.000 claims description 8
- 238000001132 ultrasonic dispersion Methods 0.000 claims description 8
- 239000010410 layer Substances 0.000 claims description 7
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 6
- UEXCJVNBTNXOEH-UHFFFAOYSA-N Ethynylbenzene Chemical group C#CC1=CC=CC=C1 UEXCJVNBTNXOEH-UHFFFAOYSA-N 0.000 claims description 6
- 229920000265 Polyparaphenylene Polymers 0.000 claims description 6
- 239000004734 Polyphenylene sulfide Substances 0.000 claims description 6
- KAESVJOAVNADME-UHFFFAOYSA-N Pyrrole Chemical compound C=1C=CNC=1 KAESVJOAVNADME-UHFFFAOYSA-N 0.000 claims description 6
- YTPLMLYBLZKORZ-UHFFFAOYSA-N Thiophene Chemical compound C=1C=CSC=1 YTPLMLYBLZKORZ-UHFFFAOYSA-N 0.000 claims description 6
- ROOXNKNUYICQNP-UHFFFAOYSA-N ammonium persulfate Chemical compound [NH4+].[NH4+].[O-]S(=O)(=O)OOS([O-])(=O)=O ROOXNKNUYICQNP-UHFFFAOYSA-N 0.000 claims description 6
- 238000004090 dissolution Methods 0.000 claims description 6
- 229920001197 polyacetylene Polymers 0.000 claims description 6
- 229920000767 polyaniline Polymers 0.000 claims description 6
- 229920000069 polyphenylene sulfide Polymers 0.000 claims description 6
- 229920000128 polypyrrole Polymers 0.000 claims description 6
- 229920000123 polythiophene Polymers 0.000 claims description 6
- GKWLILHTTGWKLQ-UHFFFAOYSA-N 2,3-dihydrothieno[3,4-b][1,4]dioxine Chemical compound O1CCOC2=CSC=C21 GKWLILHTTGWKLQ-UHFFFAOYSA-N 0.000 claims description 5
- 230000035484 reaction time Effects 0.000 claims description 5
- 239000002904 solvent Substances 0.000 claims description 5
- OEFNHCPKKJVIDJ-UHFFFAOYSA-L P(=O)(OO)([O-])[O-].[Fe+2] Chemical compound P(=O)(OO)([O-])[O-].[Fe+2] OEFNHCPKKJVIDJ-UHFFFAOYSA-L 0.000 claims description 4
- CWYNVVGOOAEACU-UHFFFAOYSA-N Fe2+ Chemical compound [Fe+2] CWYNVVGOOAEACU-UHFFFAOYSA-N 0.000 claims description 3
- 229910002651 NO3 Inorganic materials 0.000 claims description 3
- NHNBFGGVMKEFGY-UHFFFAOYSA-N Nitrate Chemical compound [O-][N+]([O-])=O NHNBFGGVMKEFGY-UHFFFAOYSA-N 0.000 claims description 3
- AZDRQVAHHNSJOQ-UHFFFAOYSA-N alumane Chemical class [AlH3] AZDRQVAHHNSJOQ-UHFFFAOYSA-N 0.000 claims description 3
- 229910052782 aluminium Inorganic materials 0.000 claims description 3
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 claims description 3
- 229910001870 ammonium persulfate Inorganic materials 0.000 claims description 3
- 150000001868 cobalt Chemical class 0.000 claims description 3
- 239000010941 cobalt Substances 0.000 claims description 3
- 229910017052 cobalt Inorganic materials 0.000 claims description 3
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 claims description 3
- LTYMSROWYAPPGB-UHFFFAOYSA-N diphenyl sulfide Chemical compound C=1C=CC=CC=1SC1=CC=CC=C1 LTYMSROWYAPPGB-UHFFFAOYSA-N 0.000 claims description 3
- 229960002089 ferrous chloride Drugs 0.000 claims description 3
- NMCUIPGRVMDVDB-UHFFFAOYSA-L iron dichloride Chemical compound Cl[Fe]Cl NMCUIPGRVMDVDB-UHFFFAOYSA-L 0.000 claims description 3
- 150000002815 nickel Chemical class 0.000 claims description 3
- 229910052759 nickel Inorganic materials 0.000 claims description 3
- 125000000843 phenylene group Chemical group C1(=C(C=CC=C1)*)* 0.000 claims description 3
- 229930192474 thiophene Natural products 0.000 claims description 3
- 150000003608 titanium Chemical class 0.000 claims description 3
- 150000003657 tungsten Chemical class 0.000 claims description 3
- WFKWXMTUELFFGS-UHFFFAOYSA-N tungsten Chemical compound [W] WFKWXMTUELFFGS-UHFFFAOYSA-N 0.000 claims description 3
- 229910052721 tungsten Inorganic materials 0.000 claims description 3
- 239000010937 tungsten Substances 0.000 claims description 3
- 150000003681 vanadium Chemical class 0.000 claims description 3
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims description 3
- NLXLAEXVIDQMFP-UHFFFAOYSA-N Ammonium chloride Substances [NH4+].[Cl-] NLXLAEXVIDQMFP-UHFFFAOYSA-N 0.000 claims description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 claims description 2
- BAUYGSIQEAFULO-UHFFFAOYSA-L iron(2+) sulfate (anhydrous) Chemical compound [Fe+2].[O-]S([O-])(=O)=O BAUYGSIQEAFULO-UHFFFAOYSA-L 0.000 claims 2
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 26
- SURQXAFEQWPFPV-UHFFFAOYSA-L iron(2+) sulfate heptahydrate Chemical compound O.O.O.O.O.O.O.[Fe+2].[O-]S([O-])(=O)=O SURQXAFEQWPFPV-UHFFFAOYSA-L 0.000 description 22
- 239000000463 material Substances 0.000 description 17
- 229910052744 lithium Inorganic materials 0.000 description 15
- 230000000052 comparative effect Effects 0.000 description 14
- DCKVFVYPWDKYDN-UHFFFAOYSA-L oxygen(2-);titanium(4+);sulfate Chemical compound [O-2].[Ti+4].[O-]S([O-])(=O)=O DCKVFVYPWDKYDN-UHFFFAOYSA-L 0.000 description 12
- 239000012047 saturated solution Substances 0.000 description 12
- 238000001878 scanning electron micrograph Methods 0.000 description 12
- 229910000348 titanium sulfate Inorganic materials 0.000 description 12
- 239000012071 phase Substances 0.000 description 10
- 238000006243 chemical reaction Methods 0.000 description 8
- 239000010406 cathode material Substances 0.000 description 7
- 229910000398 iron phosphate Inorganic materials 0.000 description 7
- 238000009776 industrial production Methods 0.000 description 6
- 239000006012 monoammonium phosphate Substances 0.000 description 6
- 238000006116 polymerization reaction Methods 0.000 description 6
- 229920000642 polymer Polymers 0.000 description 5
- 238000012360 testing method Methods 0.000 description 5
- 238000005260 corrosion Methods 0.000 description 4
- 230000007797 corrosion Effects 0.000 description 4
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- 230000000694 effects Effects 0.000 description 2
- 238000001027 hydrothermal synthesis Methods 0.000 description 2
- 238000011065 in-situ storage Methods 0.000 description 2
- 238000009830 intercalation Methods 0.000 description 2
- 230000002687 intercalation Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 230000003647 oxidation Effects 0.000 description 2
- 238000007254 oxidation reaction Methods 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000003980 solgel method Methods 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- 229910010710 LiFePO Inorganic materials 0.000 description 1
- 229920001609 Poly(3,4-ethylenedioxythiophene) Polymers 0.000 description 1
- HFCVPDYCRZVZDF-UHFFFAOYSA-N [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O Chemical compound [Li+].[Co+2].[Ni+2].[O-][Mn]([O-])(=O)=O HFCVPDYCRZVZDF-UHFFFAOYSA-N 0.000 description 1
- 230000002411 adverse Effects 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 239000002131 composite material Substances 0.000 description 1
- 150000001875 compounds Chemical class 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- QHGJSLXSVXVKHZ-UHFFFAOYSA-N dilithium;dioxido(dioxo)manganese Chemical compound [Li+].[Li+].[O-][Mn]([O-])(=O)=O QHGJSLXSVXVKHZ-UHFFFAOYSA-N 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000011049 filling Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 238000009616 inductively coupled plasma Methods 0.000 description 1
- AFSWOABZOLEQMR-UHFFFAOYSA-J iron(4+);hydroxide;phosphate Chemical compound [OH-].[Fe+4].[O-]P([O-])([O-])=O AFSWOABZOLEQMR-UHFFFAOYSA-J 0.000 description 1
- 229910000625 lithium cobalt oxide Inorganic materials 0.000 description 1
- BFZPBUKRYWOWDV-UHFFFAOYSA-N lithium;oxido(oxo)cobalt Chemical compound [Li+].[O-][Co]=O BFZPBUKRYWOWDV-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000002441 reversible effect Effects 0.000 description 1
- 238000003746 solid phase reaction Methods 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 238000006467 substitution reaction Methods 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 230000002194 synthesizing effect Effects 0.000 description 1
Classifications
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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
- H01M4/362—Composites
- H01M4/366—Composites as layered products
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M10/00—Secondary cells; Manufacture thereof
- H01M10/05—Accumulators with non-aqueous electrolyte
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- 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
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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
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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
- H01M4/60—Selection of substances as active materials, active masses, active liquids of organic compounds
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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
- H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
- H01M2004/028—Positive electrodes
-
- 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 lithium iron phosphate positive electrode material, a preparation method and application thereof, wherein the lithium iron phosphate positive electrode material comprises an inner core layer and an outer coating layer, the inner core layer is doped with metal element hydroxyl ferric phosphate, and the chemical structural formula is as follows: [ Fe x M y (PO 4 )](OH), wherein M is a metal element, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1-x, and the outer coating layer is a conductive polymer. The preparation method comprises the following steps: stirring and mixing an iron source and a saturated metal salt solution uniformly; adding phosphoric acid, excessive oxidant, ammonium dihydrogen phosphate and sodium dodecyl benzene sulfonate, stirring, adding ammonia water solution, heating, cooling to room temperature, filtering, washing and drying to obtain metal element-doped hydroxyl ferric phosphate; it is subjected toAdding conductive high molecular monomer into water, ultrasonic dispersing and stirring to obtain turbid liquid; and adding an initiator into the turbid liquid, continuously stirring to obtain a precipitate, and centrifuging, washing and drying to obtain the conductive polymer coated lithium iron phosphate anode material doped with the metal element hydroxyl ferric phosphate.
Description
Technical Field
The invention belongs to the field of lithium ion battery anode materials, and particularly relates to a lithium iron phosphate anode material, a preparation method and application thereof.
Background
As a representative secondary battery with the highest comprehensive performance, commercialization of lithium ion batteries can be traced to the 90 th century at the earliest, and research on lithium ion batteries has been conducted for many years to have a mature battery technology route. The lithium ion secondary battery has the advantages of high energy density, excellent cycle performance and the like, is considered to be an ideal high-capacity high-power battery, is widely applied to the fields of portable electric appliances, military equipment and the like, and can also be applied to power batteries of electric automobiles and hybrid electric automobiles. Lithium iron phosphate (LiFePO) 4 ) The lithium ion battery has the advantages of being capable of reversibly inserting and extracting lithium, high in specific capacity, good in cycle performance, stable in electrochemical performance, low in price and the like, and is a first-choice green positive electrode material of a new generation, particularly used as a power lithium ion battery material.
However, the current lithium iron phosphate cathode materials have the following disadvantages: electron conductivity and Li + The low diffusion coefficient easily causes the lower actual reversible capacity of the material, influences the high-current charge and discharge capacity and reduces the low-temperature performance of the battery; during the preparation process, fe 2+ Is extremely easily oxidized into Fe at high temperature 3+ The compound impurities have adverse effects on the electrochemical performance of lithium iron phosphate. Moreover, the theoretical density and the actual bulk density of the lithium iron phosphate material are much lower than those of lithium cobalt oxide, lithium manganate, ternary nickel cobalt lithium manganate and other materials, so that the filling amount of the lithium iron phosphate material in the battery is relatively small, and the energy density of the battery is reduced.
At present, the method for synthesizing the lithium iron phosphate mainly comprises a high-temperature solid-phase reaction method, a sol-gel method, a hydrothermal method and a chemical lithium intercalation method, wherein in the existing synthesis method, the particle size of the lithium iron phosphate synthesized by the high-temperature solid-phase method is larger, the electrochemical performance is not ideal enough, the hydrothermal method can control the particle size, but the difficulty of industrial production is larger, the lithium iron phosphate synthesized by the sol-gel method and the chemical lithium intercalation method is ideal, but the preparation process is complex, the production period is longer, and the production cost is higher.
Disclosure of Invention
In view of the above, the present invention aims to solve at least one of the technical problems existing in the prior art. Therefore, the invention provides a lithium iron phosphate positive electrode material and a preparation method thereof. The lithium iron phosphate anode material provided by the invention has the advantages of stable structure, higher theoretical specific capacity, good corrosion resistance, good electrochemical performance, rate capability and stability. Meanwhile, the preparation method has simple process flow and is suitable for large-scale industrial production.
Therefore, in a first aspect, an embodiment of the present invention provides a lithium iron phosphate positive electrode material, where the lithium iron phosphate positive electrode material includes an inner core layer and an outer cladding layer, and the inner core layer is doped with metal element hydroxyl iron phosphate, and has a chemical structural formula as follows: [ Fe x M y (PO 4 )](OH), wherein M is a metal element, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1-x, and the outer layer coating layer is a conductive polymer.
Preferably, the metal element M is one of titanium (Ti), nickel (Ni), vanadium (V), cobalt (Co), tungsten (W), and aluminum (Al), and the conductive polymer is one or more selected from Polyacetylene (PA), polythiophene (PT), polyphenylene (PPH), polyphenylacetylene (PPA), polyaniline (PANI), polyphenylene sulfide (PPS), polypyrrole (PPy), poly-java-line (PPQ), and poly-3, 4-ethylenedioxythiophene (PEDOT).
In a second aspect, an embodiment of the present invention provides a method for preparing a lithium iron phosphate positive electrode material, where the method includes: adding a proper amount of iron source into water for dissolution, adding saturated metal salt solution, and stirring and uniformly mixing to obtain a clear solution; sequentially adding phosphoric acid and excessive oxidant into the clear solution, oxidizing for a period of time, adding ammonium dihydrogen phosphate and sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution; adding ammonia water solution into the mixed solution to adjust the pH value, sealing the reactant in an autoclave for heating, slowly cooling to room temperature, and filtering, washing and drying to obtain the metal element-doped iron hydroxy phosphate; adding a conductive high molecular monomer and the metal element-doped hydroxyl ferric phosphate into water according to a certain proportion, performing ultrasonic dispersion, stirring to obtain turbid liquid, and maintaining a certain temperature; and adding an initiator into the turbid liquid, continuously stirring and reacting for a period of time to obtain a precipitate, centrifuging, washing and drying the obtained precipitate to obtain the conductive polymer coated lithium iron phosphate anode material doped with the metal element hydroxyl ferric phosphate.
Preferably, the dissolution temperature is controlled between 50-60 ℃, the stirring speed is 300-400rpm, and the stirring time is 25-30min.
Preferably, the iron source is one or more of ferrous sulfate, aqueous ferrous sulfate, ferrous nitrate and ferrous chloride; the saturated metal salt solution is titanium salt solution, nickel salt solution, vanadium salt solution, cobalt salt solution, tungsten salt solution or aluminum salt solution.
Preferably, the oxidant is hydrogen peroxide, and the oxidation time is 1.5-2.0h; the stirring temperature is room temperature, the stirring rotating speed is 350rpm, and the stirring time is 10-20min.
Preferably, in the step S3, an aqueous ammonia solution is added to adjust the pH to 2.3-2.7, the heating temperature is 150-200 ℃, the heating time is 24 hours, and the washing solvent is absolute ethanol.
Preferably, the mass ratio of the conductive polymer monomer to the doped metal element hydroxyl ferric phosphate is 1:1, maintaining a certain temperature at 60-70 ℃, wherein the conductive high molecular monomer is one or more of acetylene, thiophene, phenylene, phenylacetylene, aniline, phenyl sulfide, pyrrole, ouline and 3, 4-ethylenedioxythiophene.
Preferably, the stirring reaction time is 12-14h, the washing solvent is absolute ethyl alcohol, and the initiator is one or more of azobisisobutyronitrile and ammonium persulfate.
In a third aspect, an embodiment of the present invention provides a lithium ion battery, where the lithium ion battery includes the lithium iron phosphate cathode material provided in the first aspect.
The lithium iron phosphate positive electrode material provided by the embodiment of the invention takes the doped metal element hydroxyl ferric phosphate as an inner core, and the conductive polymer is coated on the outer layer of the lithium iron phosphate positive electrode material, so that the lithium iron phosphate positive electrode material has the advantages of stable structure, high theoretical specific capacity and good corrosion resistance, and the lithium ion battery prepared by adopting the lithium iron phosphate positive electrode material has good electrochemical performance, multiplying power performance and stability. And the preparation method has simple process flow and is suitable for large-scale industrial production.
Drawings
FIG. 1 is a flowchart of a preparation method of a lithium iron phosphate positive electrode material provided by an embodiment of the invention;
FIG. 2 is an SEM image of the titanium-doped ferric hydroxyphosphate prepared in comparative example 1 of the present invention;
FIG. 3 is an SEM image of a lithium iron phosphate positive electrode material prepared in example 1 of the present invention;
FIG. 4 is an SEM image of a lithium iron phosphate positive electrode material prepared in example 2 of the present invention;
FIG. 5 is an SEM image of a lithium iron phosphate positive electrode material prepared in example 3 of the present invention;
FIG. 6 is an SEM image of a lithium iron phosphate positive electrode material prepared in example 4 of the present invention;
fig. 7 is an SEM image of the lithium iron phosphate positive electrode material prepared in example 5 of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
The following disclosure provides many different embodiments, or examples, for implementing different structures of the invention. In order to simplify the present disclosure, components and arrangements of specific examples are described below. They are, of course, merely examples and are not intended to limit the invention. Furthermore, the present invention may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed. In addition, the present invention provides examples of various specific processes and materials, but one of ordinary skill in the art will recognize the applicability of other processes and/or the use of other materials.
The invention aims to provide a lithium iron phosphate positive electrode material, a preparation method and application thereof. Meanwhile, the preparation method has simple process flow and is suitable for large-scale industrial production. The lithium ion battery prepared by the lithium iron phosphate anode material has good electrochemical performance, rate capability and stability.
An embodiment of the first aspect of the present invention provides a lithium iron phosphate positive electrode material, which can be used as a positive electrode material of a lithium ion battery. The lithium iron phosphate anode material comprises an inner core layer and an outer coating layer, wherein the inner core layer is doped with metal element hydroxyl ferric phosphate, and the chemical structural formula is as follows: [ Fe x M y (PO 4 )](OH), wherein M is a metal element, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1-x. Specifically, the metal element M may be one of titanium (Ti), nickel (Ni), vanadium (V), cobalt (Co), tungsten (W), and aluminum (Al). The outer layer coating layer is a conductive polymer, and specifically, the conductive polymer is one or more selected from Polyacetylene (PA), polythiophene (PT), polyphenylene (PPH), polyphenylacetylene (PPA), polyaniline (PANI), polyphenylene sulfide (PPS), polypyrrole (PPy), poly (Java-ine) (PPQ) and poly (3, 4-ethylenedioxythiophene) (PEDOT).
The lithium iron phosphate positive electrode material provided by the embodiment of the invention takes the doped metal element hydroxyl ferric phosphate as an inner core, and the conductive polymer is coated on the outer layer of the lithium iron phosphate positive electrode material, so that the lithium iron phosphate positive electrode material has the advantages of stable structure, high theoretical specific capacity and good corrosion resistance, and the lithium ion battery prepared by adopting the lithium iron phosphate positive electrode material has good electrochemical performance, multiplying power performance and stability.
An embodiment of the second aspect of the present invention provides a method for preparing a lithium iron phosphate positive electrode material, as shown in fig. 1, the method comprising the steps of:
step S1: adding a proper amount of iron source into water for dissolution, adding saturated metal salt solution, and stirring and uniformly mixing to obtain a clear solution;
wherein the dissolution temperature is controlled between 50-60 ℃, the stirring speed can be 300-400rpm, and the stirring time can be 25-30min. In the embodiment of the invention, the iron source can be one or more of ferrous sulfate, ferrous sulfate hydrate, ferrous nitrate and ferrous chloride; the saturated metal salt solution is titanium salt solution, nickel salt solution, vanadium salt solution, cobalt salt solution, tungsten salt solution or aluminum salt solution.
Step S2: sequentially adding phosphoric acid and excessive oxidant into the clear solution, oxidizing for a period of time, adding ammonium dihydrogen phosphate and sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
wherein the oxidant can be hydrogen peroxide; the oxidation time may be 1.5-2.0h. The stirring temperature is room temperature, the stirring rotating speed is 350rpm, and the stirring time can be 10-20min.
Step S3: adding ammonia water solution into the mixed solution to adjust the pH value, sealing the reactant in an autoclave for heating, slowly cooling to room temperature, and filtering, washing and drying to obtain the metal element-doped iron hydroxy phosphate;
wherein, adding ammonia water solution to adjust pH value to 2.3-2.7, heating to 150-200deg.C for 24h, and washing with anhydrous ethanol.
Step S4: adding a conductive high molecular monomer and the metal element-doped hydroxyl ferric phosphate into water according to a certain proportion, performing ultrasonic dispersion, stirring to obtain turbid liquid, and maintaining a certain temperature;
wherein, the adding mass ratio of the conductive high molecular monomer to the metal element doped hydroxy ferric phosphate is 1:1, wherein the certain temperature is kept at 60-70 ℃. In the embodiment of the invention, the conductive polymer monomer can be one or more of acetylene, thiophene, phenylene, phenylacetylene, aniline, phenyl sulfide, pyrrole, java-type or 3, 4-ethylenedioxythiophene.
Step S5: and adding an initiator into the turbid liquid, continuously stirring and reacting for a period of time to obtain a precipitate, centrifuging, washing and drying the obtained precipitate to obtain the conductive polymer coated lithium iron phosphate anode material doped with the metal element hydroxyl ferric phosphate.
Wherein the stirring reaction time can be 12-14h, and the washing solvent can be absolute ethyl alcohol. In the embodiment of the invention, the initiator can be one or more of azodiisobutyronitrile and ammonium persulfate, and the addition amount is 1g.
In the embodiment of the invention, the preparation method of the lithium iron phosphate positive electrode material adopts metal doped hydroxyl ferric phosphate as a bulk phase material, and the morphology and the performance of the bulk phase material can be optimized by controlling the conditions of the doped metal type, the reaction temperature, the stirring rate, the reaction time and the like, so that the bulk phase material of the metal doped hydroxyl ferric phosphate with high phase purity, uniform morphology and stable performance is prepared. And further mixing the bulk phase material metal doped hydroxyl ferric phosphate with a conductive high molecular monomer and an initiator, and performing in-situ polymerization to prepare the conductive high molecular coated metal doped hydroxyl ferric phosphate lithium iron phosphate battery anode material by controlling the type of the initiator, the polymerization temperature and the polymerization time. Meanwhile, the preparation method has the advantages of simple process flow, low cost, no pollution and the like, and is suitable for large-scale industrial production.
The following describes in further detail the specific procedures and effects of the preparation method of the lithium iron phosphate positive electrode material using the present invention with reference to some specific examples, but is not limited to the scope of the present invention. The specific process parameters and the like described below are also merely examples of suitable ranges, i.e., one skilled in the art can make a suitable selection from the description herein and are not intended to be limited to the specific values described below.
Comparative example 1
The embodiment provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
step S1: taking ferrous sulfate as an iron source, dissolving 10g of ferrous sulfate in 100ml of pure water, controlling the temperature to 55 ℃, taking titanium sulfate as a metal salt solution, firstly preparing 1.7g of titanium sulfate into a saturated solution, then slowly adding the saturated solution into the ferrous sulfate solution, and stirring for 10min under the condition of the rotating speed of 300rpm to obtain a clear solution;
step S2: adding 6.27g of phosphoric acid into the clear solution at a constant speed, adding 1.1g of hydrogen peroxide at a constant speed, oxidizing for 2 hours, adding 7.36g of monoammonium phosphate and 2.0g of sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value to 2.5, sealing the reactant in an autoclave, heating at 200 ℃ for 24 hours, slowly cooling to room temperature, filtering, washing with absolute ethyl alcohol, and drying to obtain 10.02g of titanium-doped ferric phosphate;
fig. 2 shows an SEM image of titanium doped iron hydroxyphosphate prepared according to comparative example 1.
Example 1
The embodiment provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
step S1: taking ferrous sulfate as an iron source, dissolving 10g of ferrous sulfate in 100ml of pure water, controlling the temperature to 55 ℃, taking titanium sulfate as a metal salt solution, firstly preparing 1.7g of titanium sulfate into a saturated solution, then slowly adding the saturated solution into the ferrous sulfate solution, and stirring for 10min under the condition of the rotating speed of 300rpm to obtain a clear solution;
step S2: adding 6.27g of phosphoric acid into the clear solution at a constant speed, adding 1.1g of hydrogen peroxide at a constant speed, oxidizing for 2 hours, adding 7.36g of monoammonium phosphate and 2.0g of sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value to 2.5, sealing the reactant in an autoclave, heating at 200 ℃ for 24 hours, slowly cooling to room temperature, filtering, washing with absolute ethyl alcohol, and drying to obtain 10.02g of titanium-doped ferric phosphate;
step S4: adding 10.02g of conductive high polymer monomer acetylene and 10.02g of titanium doped ferric phosphate hydroxide into water, performing ultrasonic dispersion, stirring to obtain turbid liquid, and keeping the temperature at 70 ℃;
step S5: adding 1.0g of initiator azodiisobutyronitrile into the turbid liquid, continuously stirring at 70 ℃ for reaction for 12 hours after the dripping is finished to obtain a precipitate, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying to obtain 19.58g of conductive polymer-coated titanium-doped ferric phosphate lithium iron anode material.
Fig. 3 is an SEM image of a lithium iron phosphate positive electrode material prepared according to example 1. The graph shows that the conductive polymer coated titanium-doped ferric phosphate lithium iron phosphate positive electrode material prepared in the embodiment has no obvious difference from the titanium-doped ferric phosphate hydroxide prepared in the comparative example 1.
Example 2
The embodiment provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
step S1: taking ferrous sulfate as an iron source, dissolving 10g of ferrous sulfate in 100ml of pure water, controlling the temperature to 55 ℃, taking titanium sulfate as a metal salt solution, firstly preparing 1.7g of titanium sulfate into a saturated solution, then slowly adding the saturated solution into the ferrous sulfate solution, and stirring for 10min under the condition of the rotating speed of 300rpm to obtain a clear solution;
step S2: adding 6.27g of phosphoric acid into the clear solution at a constant speed, adding 1.1g of hydrogen peroxide at a constant speed, oxidizing for 2 hours, adding 7.36g of monoammonium phosphate and 2.0g of sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value to 2.5, sealing the reactant in an autoclave, heating at 200 ℃ for 24 hours, slowly cooling to room temperature, filtering, washing with absolute ethyl alcohol, and drying to obtain 10.02g of titanium-doped ferric phosphate;
step S4: adding 20.04g of conductive high polymer monomer acetylene and 10.02g of titanium doped ferric phosphate hydroxide into water, performing ultrasonic dispersion, stirring to obtain turbid liquid, and keeping the temperature at 70 ℃;
step S5: adding 1.0g of initiator azodiisobutyronitrile into the turbid liquid, continuously stirring at 70 ℃ for reaction for 12 hours after the dripping is finished to obtain a precipitate, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying to obtain 30.03g of conductive polymer-coated titanium-doped ferric phosphate lithium iron anode material.
Fig. 4 is an SEM image of a lithium iron phosphate positive electrode material prepared according to example 2. The graph shows that the conductive polymer coated titanium-doped ferric phosphate lithium iron phosphate positive electrode material prepared in the embodiment has no obvious difference from the titanium-doped ferric phosphate hydroxide prepared in the comparative example 1.
Example 3
The embodiment provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
step S1: taking ferrous sulfate as an iron source, dissolving 10g of ferrous sulfate in 100ml of pure water, controlling the temperature to 55 ℃, taking titanium sulfate as a metal salt solution, firstly preparing 1.7g of titanium sulfate into a saturated solution, then slowly adding the saturated solution into the ferrous sulfate solution, and stirring for 10min under the condition of the rotating speed of 300rpm to obtain a clear solution;
step S2: adding 6.27g of phosphoric acid into the clear solution at a constant speed, adding 1.1g of hydrogen peroxide at a constant speed, oxidizing for 2 hours, adding 7.36g of monoammonium phosphate and 2.0g of sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value to 2.5, sealing the reactant in an autoclave, heating at 200 ℃ for 24 hours, slowly cooling to room temperature, filtering, washing with absolute ethyl alcohol, and drying to obtain 10.02g of titanium-doped ferric phosphate;
step S4: adding 30.06g of conductive high polymer monomer acetylene and 10.02g of titanium doped ferric phosphate hydroxide into water, performing ultrasonic dispersion, stirring to obtain turbid liquid, and keeping the temperature at 70 ℃;
step S5: adding 1.0g of initiator azodiisobutyronitrile into the turbid liquid, continuously stirring at 70 ℃ for reaction for 12 hours after the dripping is finished to obtain a precipitate, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying to obtain 40.05g of conductive polymer-coated titanium-doped ferric phosphate lithium iron anode material.
Fig. 5 is an SEM image of a lithium iron phosphate positive electrode material prepared according to example 3. The graph shows that the conductive polymer coated titanium-doped ferric phosphate lithium iron phosphate positive electrode material prepared in the embodiment has no obvious difference from the titanium-doped ferric phosphate hydroxide prepared in the comparative example 1.
Example 4
The embodiment provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
step S1: taking ferrous sulfate as an iron source, dissolving 10g of ferrous sulfate in 100ml of pure water, controlling the temperature to 55 ℃, taking titanium sulfate as a metal salt solution, firstly preparing 1.7g of titanium sulfate into a saturated solution, then slowly adding the saturated solution into the ferrous sulfate solution, and stirring for 10min under the condition of the rotating speed of 300rpm to obtain a clear solution;
step S2: adding 6.27g of phosphoric acid into the clear solution at a constant speed, adding 1.1g of hydrogen peroxide at a constant speed, oxidizing for 2 hours, adding 7.36g of monoammonium phosphate and 2.0g of sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value to 2.5, sealing the reactant in an autoclave, heating at 180 ℃ for 24 hours, slowly cooling to room temperature, filtering, washing with absolute ethyl alcohol, and drying to obtain 10.02g of titanium-doped ferric phosphate;
step S4: adding 10.02g of conductive high polymer monomer acetylene and 10.02g of titanium doped ferric phosphate hydroxide into water, performing ultrasonic dispersion, stirring to obtain turbid liquid, and keeping the temperature at 70 ℃;
step S5: adding 1.0g of initiator azodiisobutyronitrile into the turbid liquid, continuously stirring at 70 ℃ for reaction for 12 hours after the dripping is finished to obtain a precipitate, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying to obtain 19.09g of conductive polymer-coated titanium-doped ferric phosphate lithium iron anode material.
Fig. 6 is an SEM image of a lithium iron phosphate positive electrode material prepared according to example 4. The graph shows that the conductive polymer coated titanium-doped ferric phosphate lithium iron phosphate positive electrode material prepared in the embodiment has no obvious difference from the titanium-doped ferric phosphate hydroxide prepared in the comparative example 1.
Example 5
The embodiment provides a preparation method of a lithium iron phosphate positive electrode material, which comprises the following steps:
step S1: taking ferrous sulfate as an iron source, dissolving 10g of ferrous sulfate in 100ml of pure water, controlling the temperature to 55 ℃, taking titanium sulfate as a metal salt solution, firstly preparing 1.7g of titanium sulfate into a saturated solution, then slowly adding the saturated solution into the ferrous sulfate solution, and stirring for 10min under the condition of the rotating speed of 300rpm to obtain a clear solution;
step S2: adding 6.27g of phosphoric acid into the clear solution at a constant speed, adding 1.1g of hydrogen peroxide at a constant speed, oxidizing for 2 hours, adding 7.36g of monoammonium phosphate and 2.0g of sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value to 2.5, sealing the reactant in an autoclave, heating at 200 ℃ for 24 hours, slowly cooling to room temperature, filtering, washing with absolute ethyl alcohol, and drying to obtain 10.02g of titanium-doped ferric phosphate;
step S4: adding 10.02g of conductive high polymer monomer acetylene and 10.02g of titanium doped ferric phosphate hydroxide into water, performing ultrasonic dispersion, stirring to obtain turbid liquid, and keeping the temperature at 60 ℃;
step S5: adding 1.0g of initiator azodiisobutyronitrile into the turbid liquid, continuously stirring at 60 ℃ for reaction for 12 hours after the dripping is finished to obtain a precipitate, centrifuging the obtained precipitate, washing with absolute ethyl alcohol, and drying to obtain 20.01g of conductive polymer-coated titanium-doped ferric phosphate lithium iron anode material.
Fig. 7 is an SEM image of a lithium iron phosphate positive electrode material prepared according to example 5. The graph shows that the conductive polymer coated titanium-doped ferric phosphate lithium iron phosphate positive electrode material prepared in the embodiment has no obvious difference from the titanium-doped ferric phosphate hydroxide prepared in the comparative example 1.
To verify the quality of the finished lithium iron phosphate cathode material prepared by the preparation method of the lithium iron phosphate cathode material provided by the embodiment of the invention, the specific surface area, the Fe content, the P content and the Fe/P molar ratio of the lithium iron phosphate prepared in examples 1 to 4 and comparative example 1 were measured according to the national standard of carbon composite lithium iron phosphate cathode material for lithium ion batteries of GBT 30835-2014, and the doped metal content of the lithium iron phosphate cathode materials prepared in examples 1 to 5 and comparative example 1 was detected by using an inductively coupled plasma spectrometer, and the test results are shown in Table 1.
Test items and test results of Table 1, examples 1-5 and comparative example 1
| Numbering device | Specific surface area | Fe content/wt% | P content/wt% | Fe/P molar ratio | Doped metal/ppm |
| Example 1 | 5.06 | 53.83 | 30.48 | 0.983 | 2068 |
| Example 2 | 5.35 | 53.35 | 30.67 | 0.975 | 3078 |
| Example 3 | 6.21 | 53.97 | 30.89 | 0.977 | 1078 |
| Example 4 | 6.45 | 53.76 | 30.87 | 0.948 | 3016 |
| Example 5 | 6.33 | 53.25 | 30.09 | 0.923 | 3098 |
| Comparative example 1 | 5.25 | 53.55 | 30.42 | 0.961 | 2054 |
According to the above examples and the comparative examples and the comparison of the test results obtained by testing the same, the lithium iron phosphate cathode materials in examples 1 to 5 have a higher specific surface area than that of comparative example 1, which is advantageous for battery reaction, and the appropriate Fe/P molar ratio can provide a more stable structure, which is advantageous for improving the theoretical specific capacity of the battery.
In summary, the preparation method of the lithium iron phosphate positive electrode material provided by the invention adopts the metal doped hydroxyl ferric phosphate as the bulk phase material, and the morphology and the performance of the bulk phase material can be optimized by controlling the conditions of the doped metal type, the reaction temperature, the stirring rate, the reaction time and the like, so that the bulk phase material of the metal doped hydroxyl ferric phosphate with high phase purity, uniform morphology and stable performance is prepared. And further mixing the bulk phase material metal doped hydroxyl ferric phosphate with a conductive high molecular monomer and an initiator, and performing in-situ polymerization to prepare the conductive high molecular coated metal doped hydroxyl ferric phosphate lithium iron phosphate battery anode material by controlling the type of the initiator, the polymerization temperature and the polymerization time. Meanwhile, the preparation method has the advantages of simple process flow, low cost, no pollution and the like, and is suitable for large-scale industrial production.
The lithium iron phosphate positive electrode material prepared by the preparation method disclosed by the invention takes the metal element doped hydroxy ferric phosphate as an inner core, and the conductive polymer is coated on the outer layer of the lithium iron phosphate positive electrode material, so that the lithium iron phosphate positive electrode material has the advantages of stable structure, high theoretical specific capacity and good corrosion resistance. The lithium ion battery prepared by the lithium iron phosphate anode material has good electrochemical performance, rate capability and stability.
In the description of the present specification, a description referring to terms "one embodiment," "some embodiments," "examples," "specific examples," or "some examples," etc., means that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
While embodiments of the present invention have been shown and described, it will be understood by those of ordinary skill in the art that: many changes, modifications, substitutions and variations may be made to the embodiments without departing from the spirit and principles of the invention, the scope of which is defined by the claims and their equivalents.
Claims (10)
1. The lithium iron phosphate anode material is characterized by comprising an inner core layer and an outer coating layer, wherein the inner core layer is doped with metal element hydroxyl ferric phosphate, and the chemical structural formula of the lithium iron phosphate anode material is as follows: [ Fe x M y (PO 4 )](OH), wherein M is a metal element, x is more than or equal to 0 and less than or equal to 1, y is more than or equal to 0 and less than or equal to 1-x, and the outer layer coating layer is a conductive polymer.
2. The lithium iron phosphate positive electrode material according to claim 1, wherein the metal element M is one of titanium (Ti), nickel (Ni), vanadium (V), cobalt (Co), tungsten (W), aluminum (Al), and the conductive polymer is one or more selected from Polyacetylene (PA), polythiophene (PT), polyphenylene (PPH), polyphenylacetylene (PPA), polyaniline (PANI), polyphenylene sulfide (PPS), polypyrrole (PPy), poly-java-in (PPQ), and poly-3, 4-ethylenedioxythiophene (PEDOT).
3. A method for preparing the lithium iron phosphate positive electrode material according to claim 1, comprising:
step S1: adding a proper amount of iron source into water for dissolution, adding saturated metal salt solution, and stirring and uniformly mixing to obtain a clear solution;
step S2: sequentially adding phosphoric acid and excessive oxidant into the clear solution, oxidizing for a period of time, adding ammonium dihydrogen phosphate and sodium dodecyl benzene sulfonate, and stirring again to obtain a mixed solution;
step S3: adding ammonia water solution into the mixed solution to adjust the pH value, sealing the reactant in an autoclave for heating, slowly cooling to room temperature, and filtering, washing and drying to obtain the metal element-doped iron hydroxy phosphate;
step S4: adding a conductive high molecular monomer and the metal element-doped hydroxyl ferric phosphate into water according to a certain proportion, performing ultrasonic dispersion, stirring to obtain turbid liquid, and maintaining a certain temperature;
step S5: and adding an initiator into the turbid liquid, continuously stirring and reacting for a period of time to obtain a precipitate, centrifuging, washing and drying the obtained precipitate to obtain the conductive polymer coated lithium iron phosphate anode material doped with the metal element hydroxyl ferric phosphate.
4. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein in the step S1, the dissolution temperature is controlled to be 50-60 ℃, the stirring speed is 300-400rpm, and the stirring time is 25-30min.
5. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein in the step S1, the iron source is one or more of ferrous sulfate, aqueous ferrous sulfate, ferrous nitrate and ferrous chloride; the saturated metal salt solution is titanium salt solution, nickel salt solution, vanadium salt solution, cobalt salt solution, tungsten salt solution or aluminum salt solution.
6. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein in the step S2, the oxidant is hydrogen peroxide for 1.5-2.0h; the stirring temperature is room temperature, the stirring rotating speed is 350rpm, and the stirring time is 10-20min.
7. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein in the step S3, an aqueous ammonia solution is added to adjust the pH to 2.3-2.7, the heating temperature is 150-200 ℃, the heating time is 24 hours, and the washing solvent is absolute ethanol.
8. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein in the step S4, the mass ratio of the conductive polymer monomer to the doped metal element iron hydroxy phosphate is 1:1, maintaining a certain temperature at 60-70 ℃, wherein the conductive high molecular monomer is one or more of acetylene, thiophene, phenylene, phenylacetylene, aniline, phenyl sulfide, pyrrole, ouline and 3, 4-ethylenedioxythiophene.
9. The method for preparing a lithium iron phosphate positive electrode material according to claim 3, wherein in the step S5, the stirring reaction time is 12-14h, the washing solvent is absolute ethyl alcohol, and the initiator is one or more of azobisisobutyronitrile and ammonium persulfate.
10. A lithium ion battery comprising the lithium iron phosphate positive electrode material of claim 1.
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