CN116462174A - Preparation method of nano-scale lithium iron phosphate lithium ion battery anode material - Google Patents
Preparation method of nano-scale lithium iron phosphate lithium ion battery anode material Download PDFInfo
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- 229910001416 lithium ion Inorganic materials 0.000 title claims abstract description 40
- NCZYUKGXRHBAHE-UHFFFAOYSA-K [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] Chemical compound [Li+].P(=O)([O-])([O-])[O-].[Fe+2].[Li+] NCZYUKGXRHBAHE-UHFFFAOYSA-K 0.000 title claims abstract description 19
- 239000010405 anode material Substances 0.000 title claims abstract description 16
- 238000002360 preparation method Methods 0.000 title claims abstract description 13
- 239000007774 positive electrode material Substances 0.000 claims abstract description 38
- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 claims abstract description 36
- 238000001035 drying Methods 0.000 claims abstract description 29
- XEEYBQQBJWHFJM-UHFFFAOYSA-N Iron Chemical compound [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims abstract description 27
- 239000002243 precursor Substances 0.000 claims abstract description 20
- 238000006243 chemical reaction Methods 0.000 claims abstract description 19
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 claims abstract description 17
- 229910052744 lithium Inorganic materials 0.000 claims abstract description 17
- 238000000034 method Methods 0.000 claims abstract description 15
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 14
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims abstract description 14
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 14
- 239000002904 solvent Substances 0.000 claims abstract description 12
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 10
- 229910052742 iron Inorganic materials 0.000 claims abstract description 10
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 10
- 239000011574 phosphorus Substances 0.000 claims abstract description 10
- 238000003756 stirring Methods 0.000 claims abstract description 10
- 239000008367 deionised water Substances 0.000 claims abstract description 8
- 229910021641 deionized water Inorganic materials 0.000 claims abstract description 8
- 239000000725 suspension Substances 0.000 claims abstract description 8
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 8
- 238000000498 ball milling Methods 0.000 claims abstract description 7
- 238000002156 mixing Methods 0.000 claims abstract description 7
- 239000002131 composite material Substances 0.000 claims abstract description 6
- 238000010000 carbonizing Methods 0.000 claims abstract description 5
- 238000001914 filtration Methods 0.000 claims abstract description 5
- 229910021642 ultra pure water Inorganic materials 0.000 claims abstract description 5
- 239000012498 ultrapure water Substances 0.000 claims abstract description 5
- 238000005406 washing Methods 0.000 claims abstract description 5
- 238000010438 heat treatment Methods 0.000 claims abstract description 4
- LYCAIKOWRPUZTN-UHFFFAOYSA-N Ethylene glycol Chemical compound OCCO LYCAIKOWRPUZTN-UHFFFAOYSA-N 0.000 claims description 20
- WMFOQBRAJBCJND-UHFFFAOYSA-M Lithium hydroxide Chemical compound [Li+].[OH-] WMFOQBRAJBCJND-UHFFFAOYSA-M 0.000 claims description 6
- 239000007787 solid Substances 0.000 claims description 5
- 238000007605 air drying Methods 0.000 claims description 3
- 235000019441 ethanol Nutrition 0.000 claims description 3
- 239000011261 inert gas Substances 0.000 claims description 3
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 claims description 3
- 229910052757 nitrogen Inorganic materials 0.000 claims description 3
- XBDUTCVQJHJTQZ-UHFFFAOYSA-L iron(2+) sulfate monohydrate Chemical compound O.[Fe+2].[O-]S([O-])(=O)=O XBDUTCVQJHJTQZ-UHFFFAOYSA-L 0.000 claims description 2
- 229910000399 iron(III) phosphate Inorganic materials 0.000 claims description 2
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 abstract description 21
- 230000000694 effects Effects 0.000 abstract description 2
- 239000002135 nanosheet Substances 0.000 description 19
- 238000002484 cyclic voltammetry Methods 0.000 description 8
- 238000009792 diffusion process Methods 0.000 description 8
- 229910010707 LiFePO 4 Inorganic materials 0.000 description 7
- 239000003792 electrolyte Substances 0.000 description 6
- 239000002064 nanoplatelet Substances 0.000 description 6
- 238000012360 testing method Methods 0.000 description 6
- 230000008901 benefit Effects 0.000 description 5
- 239000013078 crystal Substances 0.000 description 5
- 239000000463 material Substances 0.000 description 5
- 230000014759 maintenance of location Effects 0.000 description 4
- 229910010710 LiFePO Inorganic materials 0.000 description 3
- 229910052739 hydrogen Inorganic materials 0.000 description 3
- 238000001453 impedance spectrum Methods 0.000 description 3
- 229910052760 oxygen Inorganic materials 0.000 description 3
- 238000000926 separation method Methods 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- WQZGKKKJIJFFOK-GASJEMHNSA-N Glucose Natural products OC[C@H]1OC(O)[C@H](O)[C@@H](O)[C@@H]1O WQZGKKKJIJFFOK-GASJEMHNSA-N 0.000 description 2
- 230000015572 biosynthetic process Effects 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 238000013461 design Methods 0.000 description 2
- 239000007772 electrode material Substances 0.000 description 2
- 239000008103 glucose Substances 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000007709 nanocrystallization Methods 0.000 description 2
- 230000035515 penetration Effects 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 238000003786 synthesis reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000001816 cooling Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 238000000157 electrochemical-induced impedance spectroscopy Methods 0.000 description 1
- 238000004146 energy storage Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000007429 general method Methods 0.000 description 1
- WGCNASOHLSPBMP-UHFFFAOYSA-N hydroxyacetaldehyde Natural products OCC=O WGCNASOHLSPBMP-UHFFFAOYSA-N 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
- 229910000398 iron phosphate Inorganic materials 0.000 description 1
- 238000006138 lithiation reaction Methods 0.000 description 1
- ILXAVRFGLBYNEJ-UHFFFAOYSA-K lithium;manganese(2+);phosphate Chemical compound [Li+].[Mn+2].[O-]P([O-])([O-])=O ILXAVRFGLBYNEJ-UHFFFAOYSA-K 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000002994 raw material Substances 0.000 description 1
- 230000009467 reduction Effects 0.000 description 1
- 238000004904 shortening Methods 0.000 description 1
- 238000004729 solvothermal method Methods 0.000 description 1
- 238000003860 storage 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
-
- B—PERFORMING OPERATIONS; TRANSPORTING
- B82—NANOTECHNOLOGY
- B82Y—SPECIFIC USES OR APPLICATIONS OF NANOSTRUCTURES; MEASUREMENT OR ANALYSIS OF NANOSTRUCTURES; MANUFACTURE OR TREATMENT OF NANOSTRUCTURES
- B82Y30/00—Nanotechnology for materials or surface science, e.g. nanocomposites
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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
- 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
- H01M4/58—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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
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- 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
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- 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
- C01P2006/12—Surface area
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- 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
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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
- H01M2004/021—Physical characteristics, e.g. porosity, surface area
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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
Abstract
The application relates to a preparation method of a nanoscale lithium iron phosphate lithium ion battery anode material, which comprises the following steps: s1: under the condition of room temperature, adding a lithium source and a solvent into a high-pressure reaction kettle, wherein the content of the lithium source in the solvent is 1.3-1.6 mol/L, and stirring for 15-30 min; s2: adding a phosphorus source into a high-pressure reaction kettle, and adding an iron source after uniformly stirring to ensure that the molar ratio of Li to Fe to P is 1.0-1.1:0.97-1.02:1; s3: heating the high-pressure reaction kettle to 150-180 ℃ and keeping the temperature for 1-3 h; s4: filtering the suspension obtained after the reaction, alternately washing with deionized water and absolute ethyl alcohol for 3-5 times, and finally drying to obtain a nano lithium iron phosphate precursor; s5: mixing, ball milling and drying a nano lithium iron phosphate precursor and a carbon source in ultrapure water according to the mass ratio of 1:0.1-0.3 to obtain a carbon composite precursor sample; s6: carbonizing the precursor sample in an inert atmosphere furnace at 650-800 ℃ for 3-6 hours to obtain the nanoscale lithium iron phosphate anode material. The method has the effect of improving the energy density of the lithium ion battery prepared by taking the lithium iron phosphate as the positive electrode material.
Description
Technical Field
The application relates to the technical field of lithium ion battery materials, in particular to a preparation method of a nanoscale lithium iron phosphate lithium ion battery anode material.
Background
Lithium Ion Batteries (LIBs) are currently the dominant secondary batteries for the portable electronics market and are widely regarded as potential technologies for electric vehicles and smart grids, wherein the chemistry and nanocrystallization of electrode materials have achieved improvements in LIB performance, and in the prior art, the electrode materials typically employ olivine-type lithium iron phosphate, olivine-type lithium iron phosphate (LiFePO 4 LFP) has a higher operating voltage (-3.4 v vs + ) Larger theoretical capacity (-170 mAh g) -1 ) And thermal stability and possessing the characteristics of low cost, non-toxicity and environmental friendliness, is an important positive electrode material for high-energy novel LIB design, but the low electron conductivity of LFP and one-dimensional lithium ion diffusion channel cause that such positive electrode material cannot realize the manufacture of rechargeable batteries with high energy density.
Nevertheless, the durability and energy density of LIBs are still far lower than those required for high energy transportation vehicles, and there is a need for a rechargeable battery with high energy density to meet the increasing demand for high performance energy storage systems.
Disclosure of Invention
In order to solve the problem that the energy density of a lithium ion battery prepared by taking lithium iron phosphate as a positive electrode material is low due to low electron conductivity of LFP and one-dimensional lithium ion diffusion channel, the application provides a preparation method of a nano-scale lithium iron phosphate positive electrode material of a lithium ion battery.
The preparation method of the nano-scale lithium iron phosphate lithium ion battery anode material adopts the following technical scheme:
the preparation method of the nano-scale lithium iron phosphate lithium ion battery anode material comprises the following steps:
s1: under the condition of room temperature, adding a lithium source and a solvent into a high-pressure reaction kettle, wherein the content of the lithium source in the solvent is 1.3-1.6 mol/L, and stirring for 15-30 min;
s2: adding a phosphorus source into a high-pressure reaction kettle, and adding an iron source after uniformly stirring to ensure that the molar ratio of Li to Fe to P is 1.0-1.1:0.97-1.02:1;
s3: heating the high-pressure reaction kettle to 150-180 ℃ and keeping the temperature for 1-3 h;
s4: filtering the suspension obtained after the reaction, alternately washing with deionized water and absolute ethyl alcohol for 3-5 times, and finally drying to obtain a nano lithium iron phosphate precursor;
s5: mixing and ball milling the nano lithium iron phosphate precursor and a carbon source in ultrapure water according to the mass ratio of 1:0.1-0.3, wherein the solid content is 30-35%, and then drying to obtain a carbon composite precursor sample.
S6: carbonizing the precursor sample in an inert atmosphere furnace at 650-800 ℃ for 3-6 hours to obtain the nanoscale lithium iron phosphate anode material.
Preferably: the solvent in the S1 is as follows: any one or a combination of ethylene glycol, ethanol and deionized water.
Preferably: the lithium source in S1 is: li (Li) 2 CO 3 、LiOH·H 2 O and LiH 2 PO 4 Any one of, or a combination thereof.
Preferably: the phosphorus source in the S2 is as follows: h 3 PO 4 And LiH 2 PO 4 Any one of, or a combination thereof.
Preferably: the iron source in S2 is: either FeSO4.H2O or FePO4 or a combination thereof.
Preferably: the drying equipment in the step S4 comprises a forced air drying box, wherein the drying temperature is 70-100 ℃ and the drying time is 16-25 h.
Preferably: the carbon source in the S5 is as follows: c (C) 6 H 12 O 6 、C 12 H 22 O 11 、C 6 H 8 O 7 And any one of PEG or its combination.
Preferably: and (5) mixing and ball milling for 1-3 hours in the step (S5).
Preferably: the drying equipment in the step S5 comprises a blast drying box, wherein the drying time is 10-15 h, and the drying temperature is 70-100 ℃.
Preferably: the inert gases in the S6 are Ar and N 2 Any one of, or a combination thereof.
In summary, the preparation method of the nano-scale lithium iron phosphate lithium ion battery positive electrode material has the beneficial technical effects that:
1. in the invention, the lithium source, the iron source and the phosphorus source are used as raw materials, and the lithium source, the iron source and the phosphorus source are synthesized to have high exposure [010] through combining a solvothermal method and mechanical stripping]LiFePO of face 4 A nano-sheet. LiFePO 4 The nanoplatelets can maximize their effective surface area, expose more electrode-electrolyte reaction interfaces, and allow penetration of the carbon coating and electrolyte, thereby improving their electronic conductivity and reducing diffusion paths for lithium ions. These characteristics, combined with high tap density, improve cell cathode-electrolyte interface kinetics and enhance cathode cycling stability. In addition, the method has the advantages of simple synthesis process, low manufacturing cost, compatibility with the existing industrial production and the like;
2. in the nano-scale lithium iron phosphate positive electrode material provided by the invention, the lithium ion rapid diffusion surface of [010] preferentially appears on the surface of the nano-sheet, and the nano-sheet has more electrolyte accessible active sites exposed;
3. LiFePO prepared in the present invention 4 Nanoplatelets have a number of advantages in morphology and crystal structure, including mesoporous structure, edge [010]]Directional crystal orientation and shortened lithium ion diffusion path. These characteristics are advantageous for their use as positive electrodes in lithium ion batteries, since they will accelerate the lithium ion diffusion rate, improving LiFePO 4 Exchange of lithium ions with electrolyte and reduce capacitance of lithium ions in batteryBehavior;
4. the invention provides a lithium iron phosphate nanocrystallization strategy in a preparation process, which is a general method and can be expanded to other systems, including lithium ion battery anode materials such as lithium cobaltate, lithium nickelate, lithium manganese phosphate and the like, wherein the materials can store lithium ions through an intercalation process of a crystal structure, and the design and synthesis of a lithium ion two-dimensional material are a very attractive method for balancing the size and crystal orientation of the material.
Drawings
FIG. 1 is a graph showing the specific charge and discharge capacity of the positive electrode material LFPNs-1 prepared in example 1 of the present invention;
FIG. 2 is an AC impedance spectrum of the positive electrode material LFPNs-1 prepared in example 1 of the present invention;
FIG. 3 is a cyclic voltammogram of the positive electrode material LFPNs-1 prepared in example 1 of the present invention;
FIG. 4 is a graph showing the magnification of LFPNs-2, which is the positive electrode material prepared in example 2 of the present invention;
FIG. 5 is a cyclic voltammogram of the positive electrode material LFPNs-2 prepared in example 2 of the present invention;
FIG. 6 is an AC impedance spectrum of the positive electrode material LFPNs-2 prepared in example 2 of the present invention;
FIG. 7 is a cyclic voltammogram of the positive electrode material LFPNs-3 prepared in example 3 of the present invention;
FIG. 8 is an AC impedance spectrum of the positive electrode material LFPNs-3 prepared in example 3 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present application. It will be apparent that the described embodiments are some, but not all, of the embodiments of the present application. All other embodiments, which can be made by one of ordinary skill in the art without the benefit of the present disclosure, are intended to be within the scope of the present application based on the described embodiments.
Unless defined otherwise, technical or scientific terms used herein should be given the ordinary meaning as understood by one of ordinary skill in the art to which this application belongs. As used in the specification and claims of this application, the terms "a" and "an" and the like do not denote a limitation of quantity, but rather denote the presence of at least one.
The embodiment of the application discloses a preparation method of a nano-scale lithium iron phosphate lithium ion battery anode material.
The preparation method of the nano-scale lithium iron phosphate lithium ion battery anode material comprises the following steps:
s1: under the condition of room temperature, adding a lithium source and a solvent into a high-pressure reaction kettle, wherein the content of the lithium source in the solvent is 1.3-1.6 mol/L, and stirring time is 15-30 min, and the solvent is: any one or combination of glycol, ethanol and deionized water, and the lithium source is as follows: li (Li) 2 CO 3 、LiOH·H 2 O and LiH 2 PO 4 Any one of, or a combination thereof;
s2: adding a phosphorus source into a high-pressure reaction kettle, and adding an iron source after uniformly stirring to ensure that the molar ratio of Li to Fe to P is 1.0-1.1:0.97-1.02:1, wherein the phosphorus source is as follows: h 3 PO 4 And LiH 2 PO 4 Any one or combination of the above, and the iron source is: feSO 4 ·H 2 O and FePO 4 Any one of, or a combination thereof;
s3: heating the high-pressure reaction kettle to 150-180 ℃ and keeping the temperature for 1-3 h;
s4: filtering the suspension obtained after the reaction, alternately washing the suspension with deionized water and absolute ethyl alcohol for 3-5 times, and finally drying the washed solid for a period of time: and (3) a drying process with the drying temperature of 70-100 ℃ for 16-25 h to obtain the nano lithium iron phosphate precursor.
S5: mixing and ball milling a nano lithium iron phosphate precursor and a carbon source in ultrapure water for 1-3 hours according to the mass ratio of 1:0.1-0.3, wherein the solid content is 30-35%, and then drying to obtain a carbon composite precursor sample, wherein the carbon source is as follows: c (C) 6 H 12 O 6 、C 12 H 22 O 11 、C 6 H 8 O 7 And any one of PEG or the combination thereof, the drying equipment comprises a forced air drying box, the drying time is 10-15 h, and the drying temperature is 70-100 ℃.
S6: carbonizing a precursor sample in an inert atmosphere furnace at 650-800 ℃ for 3-6 hours to obtain a nanoscale lithium iron phosphate anode material, wherein inert gases are Ar and N 2 Any one of, or a combination thereof.
Embodiment one:
the embodiment provides a nano lithium iron phosphate anode material LiFePO 4 Ns, where Li 2 CO 3 、FeSO 4 ·H 2 O and H at 85% concentration 3 PO 4 And taking Ethylene Glycol (EG) as a solvent as a lithium source, an iron source and a phosphorus source to react to generate the lithium iron phosphate nano-sheet.
The preparation process of the nanoscale lithium iron phosphate anode material mainly comprises the following steps of:
(1) 88.05mol of Li are stirred at room temperature 2 CO 3 Adding into a high-pressure reaction kettle with a capacity of 100L and containing 60L of EG (ethylene glycol) solution, and stirring for 20min;
(2) 5.7L of H with 85% concentration 3 PO 4 Adding into the suspension, stirring, adding 83.83mol FeSO into the suspension 4 ·H 2 O, such that the molar ratio of Li to Fe to P = 1.05:1:1;
(3) The autoclave was heated to 180 ℃ in an oil bath and held for 1h;
(4) Cooling the reaction kettle to room temperature, filtering the obtained suspension, alternately washing with deionized water and absolute ethyl alcohol for 3-5 times, and finally drying at 70-100 ℃ for 10-24 hours to obtain a lithium iron phosphate nano-sheet precursor;
(5) Mixing and ball milling a lithium iron phosphate nanosheet precursor and glucose accounting for 10% of the total mass of the precursor in ultrapure water for 1-3 hours, wherein the solid content is 30% -35%, and finally drying at 70-100 ℃ for 10-24 hours to obtain a carbon composite precursor sample;
(6) Glucose-coated lithium iron phosphate nanosheets are coated on N 2 Carbonizing at 750deg.C for 4h in an atmosphere furnace to obtain final productLithium iron phosphate nanoplatelets (LFPNs-1) samples.
Through detection, LFPNs-1 realizes 168mAh g under 0.1C -1 The discharge specific capacity of (2) was 4.5V, and the cutoff voltage was close to the theoretical capacity. LFPNs-1 can provide 162, 153 and 141mAh g, respectively, when operated at higher rates (0.5C, 1.0C and 2.0C) -1 Is shown (see fig. 1). Importantly, at 0.1C, the capacity retention of LFPNs-1 was 98.0% over 300 cycles with a cut-off voltage of 4.5V.
Electrochemical impedance spectroscopy and cyclic voltammetry curves revealed LiFePO coated with a thin carbon layer 4 Conductivity of the nanoplatelets. The Nyquist plot of the ac impedance shows that the electrode made from LFPNs-1 shows higher electron conductivity and lower charge transfer resistance (see fig. 2). The electron conductivity and the total resistance of the electrode made of LFPNs-1 were 1.8S cm, respectively, using a simplified equivalent circuit -2 And 75.3 Ω cm -2 Is superior to the traditional LiFePO 4 and/C composite electrode. At 0.3mV s -1 The cyclic voltammogram at a fixed scan rate of LFPNs-1 showed a potential separation between the anode and cathode peaks of about 0.55V (see fig. 3). Furthermore, the redox peak profile of LFPNs-1 is symmetrical and sharp, which suggests that due to the increase in conductivity and lithium ion edge [010]]The diffusion distance in the direction is reduced, and the redox kinetics is enhanced.
Embodiment two:
the present embodiment differs from the first embodiment in that: the autoclave was heated to 180 ℃ in an oil bath and held for 2 hours, and the electrochemical performance of the positive electrode material provided by this example was tested to be substantially the same as that provided by example 1, which example was labeled LFPNs-2.
Compared with the traditional LiFePO 4 Structure comparison, liFePO 4 Nanoplatelets have significant advantages in terms of their morphology and crystal orientation, and thus are expected to significantly improve their lithium storage properties.
The lithium iron phosphate nano-sheet positive electrode material has higher charge-discharge specific capacity and stable multiplying power circulation performance, is charged at 0.1C by 2.0-4.5V at room temperature, is discharged at 0.1C, 0.2C, 0.5C, 1.0C, 2.0C and 3.0C respectively, and is circulated for 4 weeks at each discharge multiplying power (see figure 4). The rate capability of LFPNs-2 materials is slightly improved compared with the first embodiment.
Oxidation and reduction properties are studied by Cyclic Voltammetry (CV), and the degree of lithiation and delithiation smoothness can be accurately reflected. No significant change in CV curve occurs over 3 cycles, indicating no large capacity fade, which means that stable high efficiency can be provided. At 0.3mV s -1 The potential separation between anode and cathode peaks is as low as 0.38V at the fixed scan rate and the redox peaks exhibit a more symmetrical shape (see figure 5). The Nyquist plot of the ac impedance shows that the electrode made from LFPNs-2 shows higher electron conductivity and lower charge transfer resistance (see fig. 6). The electron conductivity and the total resistance of the electrode made of LFPNs-2 were 1.9S cm, respectively, using a simplified equivalent circuit -2 And 68.7 Ω cm -2 。
Embodiment III:
the present embodiment differs from the first embodiment in that: the autoclave was heated to 180 ℃ in an oil bath and held for 3 hours, and the electrochemical performance of the positive electrode material provided in this example was slightly reduced as compared with example 1. The sample obtained in this example is labeled LFPNs-3.
Constant current charge and discharge tests are carried out on the lithium iron phosphate nano-sheet positive electrode material in the embodiment, and the test results are as follows: the lithium iron phosphate nano-sheet positive electrode material has higher charge-discharge specific capacity and stable multiplying power circulation performance, and when the charge-discharge cut-off voltage is 2.0-4.5V at about 25 ℃ at room temperature, the first charge-discharge specific capacity of the lithium iron phosphate nano-sheet positive electrode material respectively reaches 167.8mAh g at 0.1C charge-discharge multiplying power -1 And 162.2mAh g -1 The coulombic efficiency was 96.7% and the capacity retention after 300 cycles was 92.8%.
No significant change in CV curve occurred over 3 cycles, indicating no large capacity fade, which means that stable high coulombic efficiency could be provided. At 0.3mV s -1 At a fixed scan rate of (a), the potential separation between the anode and cathode peaks is as low as 0.54V and the redox peaks exhibit a more symmetrical shape (see fig. 7). The Nyquist plot of the AC impedance shows that it is made of LFPNs-3The electrodes of (a) show higher electron conductivity and lower charge transfer resistance (see fig. 8). The electron conductivity and the total resistance of the electrode made of LFPNs-3 were 1.8S cm, respectively, using a simplified equivalent circuit -2 And 85.2 Ω cm -2 . All of the above characteristics indicate that due to the edge [010]]Directional lithium ion diffusion path shortening and electrolyte passage through LiFePO 4 Good penetration of nanoplatelets, liFePO 4 The nano-sheet effectively improves the redox kinetics.
Embodiment four:
the present embodiment differs from the first embodiment in that: li (Li) 2 CO 3 、FeSO 4 ·H 2 O and H 3 PO 4 The amounts added were 83.65mol, 81.32mol and 5.7L, respectively, the molar ratio of Li to Fe to P=1:0.97:1. The electrochemical performance of the positive electrode material provided by this example was slightly inferior to that of example 1, and the sample of this example was labeled LFPNs-4.
Constant current charge and discharge tests are carried out on the lithium iron phosphate nano-sheet positive electrode material in the embodiment, and the test results are as follows: the lithium iron phosphate nano-sheet positive electrode material has higher specific charge-discharge capacity in application of lithium ion batteries, and when the charge-discharge cut-off voltage is 2.0-4.5V at about 25 ℃ at room temperature, the specific charge-discharge capacity of the lithium iron phosphate nano-sheet positive electrode material reaches 164.9mAh g respectively at 0.1C charge-discharge multiplying power -1 And 161.2mAh g -1 The coulomb efficiency was 97.8%, and the capacity retention rate after 300 cycles at 1C charge-discharge rate was 81.0%.
Fifth embodiment:
the present embodiment differs from the first embodiment in that: li (Li) 2 CO 3 、FeSO 4 ·H 2 O and H 3 PO 4 The amounts added were 92.45mol, 85.51mol and 5.7L, respectively, the molar ratio of Li to Fe to P=1.1:1.02:1. The electrochemical performance of the positive electrode material provided by this example was slightly inferior to that of example 1, and the sample of this example was labeled LFPNs-5.
Constant current charge and discharge tests are carried out on the lithium iron phosphate nano-sheet positive electrode material in the embodiment, and the test results are as follows: the lithium iron phosphate nano-sheet positive electrode materialThe lithium iron phosphate nano-sheet positive electrode material has higher specific charge-discharge capacity in application of lithium ion batteries, and when the charge-discharge cut-off voltage is 2.0-4.5V at about 25 ℃ at room temperature, the specific charge-discharge capacity of the lithium iron phosphate nano-sheet positive electrode material reaches 166.5mAh g respectively at 0.1C charge-discharge multiplying power -1 And 160.6mAh g -1 The coulomb efficiency was 96.5%, and the capacity retention rate after 300 cycles at 1C charge-discharge rate was 75.2%.
The foregoing are all preferred embodiments of the present application, and are not intended to limit the scope of the present application in any way, therefore: all equivalent changes in structure, shape and principle of this application should be covered in the protection scope of this application.
Claims (10)
1. A preparation method of a nano-scale lithium iron phosphate lithium ion battery anode material is characterized by comprising the following steps: the method comprises the following steps:
s1: under the condition of room temperature, adding a lithium source and a solvent into a high-pressure reaction kettle, wherein the content of the lithium source in the solvent is 1.3-1.6 mol/L, and stirring for 15-30 min;
s2: adding a phosphorus source into a high-pressure reaction kettle, and adding an iron source after uniformly stirring to ensure that the molar ratio of Li to Fe to P is 1.0-1.1:0.97-1.02:1;
s3: heating the high-pressure reaction kettle to 150-180 ℃ and keeping the temperature for 1-3 h;
s4: filtering the suspension obtained after the reaction, alternately washing with deionized water and absolute ethyl alcohol for 3-5 times, and finally drying to obtain a nano lithium iron phosphate precursor;
s5: mixing and ball milling a nano lithium iron phosphate precursor and a carbon source in ultrapure water according to the mass ratio of 1:0.1-0.3, wherein the solid content is 30-35%, and then drying to obtain a carbon composite precursor sample;
s6: carbonizing the precursor sample in an inert atmosphere furnace at 650-800 ℃ for 3-6 hours to obtain the nanoscale lithium iron phosphate anode material.
2. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the solvent in the S1 is as follows: any one or a combination of ethylene glycol, ethanol and deionized water.
3. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the lithium source in S1 is: li (Li) 2 CO 3 、LiOH·H 2 O and LiH 2 PO 4 Any one of, or a combination thereof.
4. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the phosphorus source in the S2 is as follows: h 3 PO 4 And LiH 2 PO 4 Any one of, or a combination thereof.
5. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the iron source in S2 is: either FeSO4.H2O or FePO4 or a combination thereof.
6. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the drying equipment in the step S4 comprises a forced air drying box, wherein the drying temperature is 70-100 ℃ and the drying time is 16-25 h.
7. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the carbon source in the S5 is as follows: c (C) 6 H 12 O 6 、C 12 H 22 O 11 、C 6 H 8 O 7 And any one of PEG or its combination.
8. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: and (5) mixing and ball milling for 1-3 hours in the step (S5).
9. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the drying equipment in the step S5 comprises a blast drying box, wherein the drying time is 10-15 h, and the drying temperature is 70-100 ℃.
10. The method for preparing the nano-scale lithium iron phosphate lithium ion battery positive electrode material according to claim 1, which is characterized in that: the inert gases in the S6 are Ar and N 2 Any one of, or a combination thereof.
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