CN114373932A - Preparation method of nitrogen-doped carbon-coated lithium iron phosphate with lignin as source - Google Patents
Preparation method of nitrogen-doped carbon-coated lithium iron phosphate with lignin as source Download PDFInfo
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- 229920005610 lignin Polymers 0.000 title claims abstract description 163
- 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 116
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 title claims abstract description 45
- 229910052799 carbon Inorganic materials 0.000 title claims abstract description 45
- 238000002360 preparation method Methods 0.000 title claims abstract description 31
- 239000002243 precursor Substances 0.000 claims abstract description 120
- 238000000576 coating method Methods 0.000 claims abstract description 51
- 238000001354 calcination Methods 0.000 claims abstract description 50
- 239000011248 coating agent Substances 0.000 claims abstract description 46
- 238000006243 chemical reaction Methods 0.000 claims abstract description 36
- 238000002156 mixing Methods 0.000 claims abstract description 32
- 239000012954 diazonium Substances 0.000 claims abstract description 23
- 150000001989 diazonium salts Chemical class 0.000 claims abstract description 23
- 238000000034 method Methods 0.000 claims abstract description 14
- MHAJPDPJQMAIIY-UHFFFAOYSA-N Hydrogen peroxide Chemical compound OO MHAJPDPJQMAIIY-UHFFFAOYSA-N 0.000 claims description 56
- 239000000463 material Substances 0.000 claims description 42
- 239000003513 alkali Substances 0.000 claims description 31
- 239000011247 coating layer Substances 0.000 claims description 31
- 239000012295 chemical reaction liquid Substances 0.000 claims description 30
- PAYRUJLWNCNPSJ-UHFFFAOYSA-N Aniline Chemical compound NC1=CC=CC=C1 PAYRUJLWNCNPSJ-UHFFFAOYSA-N 0.000 claims description 28
- 239000003960 organic solvent Substances 0.000 claims description 26
- 238000003756 stirring Methods 0.000 claims description 24
- LPXPTNMVRIOKMN-UHFFFAOYSA-M sodium nitrite Chemical compound [Na+].[O-]N=O LPXPTNMVRIOKMN-UHFFFAOYSA-M 0.000 claims description 22
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 22
- 229920000642 polymer Polymers 0.000 claims description 18
- 150000001448 anilines Chemical class 0.000 claims description 16
- ZMXDDKWLCZADIW-UHFFFAOYSA-N N,N-Dimethylformamide Chemical compound CN(C)C=O ZMXDDKWLCZADIW-UHFFFAOYSA-N 0.000 claims description 12
- 235000010288 sodium nitrite Nutrition 0.000 claims description 11
- IAZDPXIOMUYVGZ-UHFFFAOYSA-N Dimethylsulphoxide Chemical compound CS(C)=O IAZDPXIOMUYVGZ-UHFFFAOYSA-N 0.000 claims description 8
- WYURNTSHIVDZCO-UHFFFAOYSA-N Tetrahydrofuran Chemical compound C1CCOC1 WYURNTSHIVDZCO-UHFFFAOYSA-N 0.000 claims description 8
- 239000010405 anode material Substances 0.000 claims description 8
- 239000012159 carrier gas Substances 0.000 claims description 7
- 238000001816 cooling Methods 0.000 claims description 7
- 238000001035 drying Methods 0.000 claims description 7
- 239000000203 mixture Substances 0.000 claims description 7
- 238000005406 washing Methods 0.000 claims description 7
- ALYNCZNDIQEVRV-UHFFFAOYSA-N 4-aminobenzoic acid Chemical compound NC1=CC=C(C(O)=O)C=C1 ALYNCZNDIQEVRV-UHFFFAOYSA-N 0.000 claims description 6
- 235000017166 Bambusa arundinacea Nutrition 0.000 claims description 6
- 235000017491 Bambusa tulda Nutrition 0.000 claims description 6
- 241001330002 Bambuseae Species 0.000 claims description 6
- 235000015334 Phyllostachys viridis Nutrition 0.000 claims description 6
- 229920001131 Pulp (paper) Polymers 0.000 claims description 6
- 239000011425 bamboo Substances 0.000 claims description 6
- 238000001704 evaporation Methods 0.000 claims description 6
- 239000002904 solvent Substances 0.000 claims description 6
- RYHBNJHYFVUHQT-UHFFFAOYSA-N 1,4-Dioxane Chemical compound C1COCCO1 RYHBNJHYFVUHQT-UHFFFAOYSA-N 0.000 claims description 4
- 241000209140 Triticum Species 0.000 claims description 4
- 235000021307 Triticum Nutrition 0.000 claims description 4
- 150000007522 mineralic acids Chemical class 0.000 claims description 4
- 238000000638 solvent extraction Methods 0.000 claims description 4
- 239000010902 straw Substances 0.000 claims description 4
- YLQBMQCUIZJEEH-UHFFFAOYSA-N tetrahydrofuran Natural products C=1C=COC=1 YLQBMQCUIZJEEH-UHFFFAOYSA-N 0.000 claims description 4
- TYMLOMAKGOJONV-UHFFFAOYSA-N 4-nitroaniline Chemical compound NC1=CC=C([N+]([O-])=O)C=C1 TYMLOMAKGOJONV-UHFFFAOYSA-N 0.000 claims description 3
- 229960004050 aminobenzoic acid Drugs 0.000 claims description 3
- BLFLLBZGZJTVJG-UHFFFAOYSA-N benzocaine Chemical compound CCOC(=O)C1=CC=C(N)C=C1 BLFLLBZGZJTVJG-UHFFFAOYSA-N 0.000 claims description 3
- BHAAPTBBJKJZER-UHFFFAOYSA-N p-anisidine Chemical compound COC1=CC=C(N)C=C1 BHAAPTBBJKJZER-UHFFFAOYSA-N 0.000 claims description 3
- 230000007071 enzymatic hydrolysis Effects 0.000 claims description 2
- 238000006047 enzymatic hydrolysis reaction Methods 0.000 claims description 2
- 230000001376 precipitating effect Effects 0.000 claims description 2
- 238000011031 large-scale manufacturing process Methods 0.000 abstract description 3
- 239000007772 electrode material Substances 0.000 abstract description 2
- 239000000243 solution Substances 0.000 description 72
- HEMHJVSKTPXQMS-UHFFFAOYSA-M Sodium hydroxide Chemical compound [OH-].[Na+] HEMHJVSKTPXQMS-UHFFFAOYSA-M 0.000 description 30
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 description 22
- 230000001276 controlling effect Effects 0.000 description 22
- QAOWNCQODCNURD-UHFFFAOYSA-N Sulfuric acid Chemical compound OS(O)(=O)=O QAOWNCQODCNURD-UHFFFAOYSA-N 0.000 description 20
- 229910052757 nitrogen Inorganic materials 0.000 description 12
- YXFVVABEGXRONW-UHFFFAOYSA-N Toluene Natural products CC1=CC=CC=C1 YXFVVABEGXRONW-UHFFFAOYSA-N 0.000 description 10
- 230000000052 comparative effect Effects 0.000 description 10
- 210000002969 egg yolk Anatomy 0.000 description 10
- 230000000694 effects Effects 0.000 description 8
- 239000008367 deionised water Substances 0.000 description 7
- 229910021641 deionized water Inorganic materials 0.000 description 7
- 239000007788 liquid Substances 0.000 description 7
- 102000002322 Egg Proteins Human genes 0.000 description 6
- 108010000912 Egg Proteins Proteins 0.000 description 6
- 235000013345 egg yolk Nutrition 0.000 description 6
- 238000001556 precipitation Methods 0.000 description 5
- 238000004537 pulping Methods 0.000 description 5
- 125000003944 tolyl group Chemical group 0.000 description 5
- 239000002699 waste material Substances 0.000 description 5
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 4
- ZTOZIUYGNMLJES-UHFFFAOYSA-K [Li+].[C+4].[Fe+2].[O-]P([O-])([O-])=O Chemical compound [Li+].[C+4].[Fe+2].[O-]P([O-])([O-])=O ZTOZIUYGNMLJES-UHFFFAOYSA-K 0.000 description 4
- 210000004027 cell Anatomy 0.000 description 4
- 229910001416 lithium ion Inorganic materials 0.000 description 4
- 230000001105 regulatory effect Effects 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000005516 engineering process Methods 0.000 description 3
- QJGQUHMNIGDVPM-UHFFFAOYSA-N nitrogen group Chemical group [N] QJGQUHMNIGDVPM-UHFFFAOYSA-N 0.000 description 3
- 239000005416 organic matter Substances 0.000 description 3
- 241000196324 Embryophyta Species 0.000 description 2
- QCWXUUIWCKQGHC-UHFFFAOYSA-N Zirconium Chemical compound [Zr] QCWXUUIWCKQGHC-UHFFFAOYSA-N 0.000 description 2
- 238000000498 ball milling Methods 0.000 description 2
- 239000011324 bead Substances 0.000 description 2
- 230000008859 change Effects 0.000 description 2
- 239000013078 crystal Substances 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 229910000399 iron(III) phosphate Inorganic materials 0.000 description 2
- -1 methoxyl groups Chemical group 0.000 description 2
- 239000011259 mixed solution Substances 0.000 description 2
- 239000002245 particle Substances 0.000 description 2
- 238000011056 performance test Methods 0.000 description 2
- 230000008569 process Effects 0.000 description 2
- 239000000047 product Substances 0.000 description 2
- 239000002994 raw material Substances 0.000 description 2
- 239000011573 trace mineral Substances 0.000 description 2
- 235000013619 trace mineral Nutrition 0.000 description 2
- 229910052726 zirconium Inorganic materials 0.000 description 2
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 1
- 229910019142 PO4 Inorganic materials 0.000 description 1
- 230000002378 acidificating effect Effects 0.000 description 1
- 229910052782 aluminium Inorganic materials 0.000 description 1
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 1
- 150000003863 ammonium salts Chemical class 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000011230 binding agent Substances 0.000 description 1
- 239000006227 byproduct Substances 0.000 description 1
- 230000003197 catalytic effect Effects 0.000 description 1
- 238000005253 cladding Methods 0.000 description 1
- 238000004891 communication Methods 0.000 description 1
- 238000005056 compaction Methods 0.000 description 1
- 239000006258 conductive agent Substances 0.000 description 1
- 125000000664 diazo group Chemical group [N-]=[N+]=[*] 0.000 description 1
- 229940079593 drug Drugs 0.000 description 1
- 239000003814 drug Substances 0.000 description 1
- 239000003792 electrolyte Substances 0.000 description 1
- 230000007613 environmental effect Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000000605 extraction Methods 0.000 description 1
- 239000011888 foil Substances 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000003780 insertion Methods 0.000 description 1
- 230000037431 insertion Effects 0.000 description 1
- 150000002500 ions Chemical class 0.000 description 1
- 229910052744 lithium Inorganic materials 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 229910052751 metal Inorganic materials 0.000 description 1
- 239000002184 metal Substances 0.000 description 1
- GRVDJDISBSALJP-UHFFFAOYSA-N methyloxidanyl Chemical group [O]C GRVDJDISBSALJP-UHFFFAOYSA-N 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003647 oxidation Effects 0.000 description 1
- 238000007254 oxidation reaction Methods 0.000 description 1
- 239000000825 pharmaceutical preparation Substances 0.000 description 1
- 229940127557 pharmaceutical product Drugs 0.000 description 1
- 229910052698 phosphorus Inorganic materials 0.000 description 1
- 238000007581 slurry coating method Methods 0.000 description 1
- 238000001291 vacuum drying Methods 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
- H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
- H01M4/624—Electric conductive fillers
- H01M4/625—Carbon or graphite
-
- 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
- H01M4/366—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
- 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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- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Electrochemistry (AREA)
- General Chemical & Material Sciences (AREA)
- Composite Materials (AREA)
- Engineering & Computer Science (AREA)
- Crystallography & Structural Chemistry (AREA)
- Inorganic Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The application relates to the technical field of electrode materials, in particular to a method for preparing nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source. The preparation method of the nitrogen-doped carbon-coated lithium iron phosphate with lignin as a source comprises the following steps: s1, preparing a demethoxylated lignin reaction solution; s2, preparing a diazonium salt reaction solution; s3, mixing and reacting; s4, preparing a coating precursor solution; s5, suspending lithium iron phosphate; s6, preparing precursor-coated lithium iron phosphate; and S7, calcining. The preparation method can improve the uniformity of source nitrogen-doped carbon coating, the coating method is simple and reliable, large-scale production is facilitated, and the prepared source nitrogen-doped lithium iron phosphate has good electrochemical performance, so that the electronic conductivity and the conductivity rate of the source nitrogen-doped lithium iron phosphate are greatly improved, and the preparation method has good application prospect and industrialization potential.
Description
Technical Field
The application relates to the technical field of electrode materials, in particular to a method for preparing nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source.
Background
With the development of economy and the improvement of the living standard of people, people have stronger and stronger requirements on batteries with high energy density, and lithium ion batteries have the advantages of high working voltage, high energy density, long cycle life, small self-discharge rate, environmental protection and the like, and become the development trend of secondary batteries. The method is widely applied to the fields of wireless communication, digital cameras and the like. Lithium iron phosphate has the characteristics of long cycle life, good safety, low price and the like, so that the lithium iron phosphate is widely applied to the anode material of the lithium ion battery. However, the crystal structure of lithium iron phosphate does not have continuous FePO4A coterminous octahedral network, and PO4The tetrahedra transverse to the unit cell and obstructing FePO4The interval change between crystals affects the insertion and extraction of lithium ions, so that the electronic conductivity and the ion diffusivity of the lithium iron phosphate are low, and the conductivity and the electrochemical performance of the lithium iron phosphate are poor.
In the related technology, yolk liquid is obtained by stirring fresh egg yolk, then the yolk liquid is uniformly mixed with lithium iron phosphate, and the mixture is dried and calcined; or a nitrogen-containing organic matter blending mode is added in the secondary sanding process for preparing the lithium iron phosphate, and nitrogen elements are compounded in the lithium iron phosphate so as to improve the conductivity and the electrochemical performance of the lithium iron phosphate. However, P, N in egg yolk is a trace element, and the content of the trace element is not adjustable, so that the coating effect is unstable and uncontrollable. The mode that adds nitrogenous organic matter and blend in preparation lithium iron phosphate secondary sanding process then can lead to the coating to be thicker, is difficult for improving compaction density, and nitrogen content is difficult for adjusting and control in the nitrogenous organic matter simultaneously, only relies on sanding blend to realize the coating, and the cladding material can have inhomogeneous condition. Therefore, the coating effect of the nitrogen source on the lithium iron phosphate is poor, and the conductivity and the electrochemical performance of the lithium iron phosphate are required to be further improved.
Disclosure of Invention
In order to improve the coating effect of a nitrogen source on lithium iron phosphate, the application provides a preparation method of carbon-coated lithium iron phosphate doped with lignin as a source nitrogen.
The preparation method of the nitrogen-doped carbon-coated lithium iron phosphate with lignin as the source adopts the following technical scheme:
a preparation method of nitrogen-doped carbon-coated lithium iron phosphate with lignin as a source comprises the following steps:
s1, preparation of demethoxylated lignin reaction liquid: mixing 1-40 parts by weight of lignin material and 50-3000 parts by weight of water, adjusting the pH to 8-12, adding 0.1-10 parts by weight of hydrogen peroxide at 10-100 ℃, mixing and stirring for 1-5h, and cooling to room temperature to obtain demethoxylated lignin reaction liquid;
s2, preparing a diazonium salt reaction solution: according to the weight portion, 0.1-10 portions of aniline or aniline derivatives and 5-2000 portions of water are stirred and mixed, inorganic acid is added, the pH value is adjusted to 1-3, and the mixture reacts for 10-40min at the temperature of 0-5 ℃ to obtain a first reaction liquid; stirring and mixing the first reaction solution and 0.1-10 parts of sodium nitrite, and reacting for 1-5h at 0-5 ℃ to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction liquid obtained in the step S1 and the diazonium salt reaction liquid obtained in the step S2 in parts by weight, adjusting the pH to 8-12, stirring and reacting at 0-5 ℃ for 1-5 hours, and adding inorganic acid to adjust the pH to 1-3 to obtain a second reaction liquid; standing, precipitating, washing and drying the second reaction solution to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: mixing 1-20 parts by weight of lignin azo polymer and 1000 parts by weight of organic solvent, and stirring at normal temperature to obtain a coating precursor solution;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coated precursor solution in the step S4, conveying the atomized coated precursor solution to the fluidized bed reactor in the step S5, and controlling the temperature of the fluidized bed reactor to be 70-130 ℃ to obtain precursor-coated lithium iron phosphate;
s7, calcining: and calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate.
By adopting the technical scheme, the lignin material is widely derived from natural plant products, is large in quantity, and is low in price and renewable compared with egg yolk; in addition, the content of nitrogen introduced by the lignin can be regulated, and carbon can be doped while introducing a nitrogen source, so that the conductivity of the lithium iron phosphate is further improved; the fluidized bed coating technology of the step S5-the step S6 can improve the uniformity of source nitrogen-doped carbon coating, the coating particle size is nanometer, the coating method is simple and reliable, and large-scale production is facilitated, and the prepared source nitrogen-doped carbon lithium iron phosphate has good electrochemical performance, so that the source nitrogen-doped carbon lithium iron phosphate has good electronic conductivity and conductivity multiplying power, and has good application prospect and industrialization potential.
Preferably, the lignin material in step S1 is alkali lignin, and the alkali lignin includes one or more of wheat straw alkali lignin, bamboo pulp alkali lignin, wood pulp alkali lignin, enzymatic hydrolysis lignin and organic solvent extraction type lignin.
By adopting the technical scheme, the alkali lignin is used as a main byproduct of the pulping and papermaking waste liquid, so that the environment pollution is easily caused. In addition, the wheat straw alkali lignin, the bamboo pulp alkali lignin, the wood pulp alkali lignin, the enzymolysis lignin and the organic solvent extraction type lignin all contain rich nitrogen and carbon elements and can be regulated and controlled in the coating process, so that the stability and controllability of the coating effect can be improved, and the electrochemical performance and the conductivity of the lithium iron phosphate are further improved.
Preferably, the mass ratio of the lignin material to the hydrogen peroxide in step S1 is 1 to 40.
By adopting the technical scheme, the alkali lignin can be selectively used in the pulping and papermaking waste liquid, and the alkali lignin in the pulping and papermaking waste liquid has a complex structure, so that the mass ratio of the lignin to the hydrogen peroxide is 1-40, the hydrogen peroxide is convenient to perform catalytic oxidation on the alkali lignin, the steric hindrance of methoxyl is eliminated, and the reaction activity of the alkali lignin is increased. The pH of the solution is adjusted to 8 to 12 in step S1 in order to dissolve the lignin material.
Preferably, the molar ratio of the aniline or aniline derivative to the sodium nitrite in step S2 is controlled to be 0.8-1.5.
By adopting the technical scheme, in the step S2, aniline or aniline derivatives is weighed and mixed with water, and then ammonium salt is fully formed under acidic and low-temperature conditions. Under the same condition, adding sodium nitrite, and controlling the molar ratio of aniline or aniline derivative and sodium nitrite at 0.8-1.5, so that the diazo salt can be easily obtained. In step S3, the oxidized alkali lignin, i.e., the demethoxylated lignin reaction solution and the diazonium salt reaction solution are mixed and then reacted under the conditions of alkalinity and low temperature, so as to obtain the lignin azo polymer finally.
Preferably, the aniline derivative in step S2 is any one of p-nitroaniline, p-aminobenzoic acid, ethyl p-aminobenzoate, and p-anisidine.
By adopting the technical scheme, the method has the advantages that,
preferably, the organic solvent in step S3 is any one of tetrahydrofuran, dimethyl sulfoxide, dimethylformamide and dioxane.
By adopting the technical scheme, tetrahydrofuran, dimethyl sulfoxide, dimethylformamide and dioxane can enable the lignin azo polymer to be well dissolved, and the volatility at normal temperature is weak, so that the stability of the dissolved lignin azo polymer is convenient to improve.
Preferably, in the precursor-coated lithium iron phosphate in step S6, the mass percentage of the precursor coating layer to the precursor-coated lithium iron phosphate is 0.2% to 5%, and the thickness of the precursor coating layer is 2nm to 50 nm.
By adopting the technical scheme, the uniform and stable coating layer can be formed in the mass percentage and the thickness within the range, so that the coating effect is improved, and the electrochemical performance and the conductivity of the source nitrogen-doped carbon-coated lithium iron phosphate are improved.
Preferably, the flow rate of the delivery of the coating precursor solution in step S6 is 50-100 mL/h.
By adopting the technical scheme, the uniformity of the source nitrogen-doped carbon coating is improved, so that the electrochemical performance of the source nitrogen-doped carbon-coated lithium iron phosphate is improved, and the conductivity of the source nitrogen-doped carbon-coated lithium iron phosphate is improved.
Preferably, the temperature of the calcination treatment in step S7 is 550-900 ℃, and the calcination time is 2-12 h.
By adopting the technical scheme, the lithium iron phosphate coated by the precursor is easy to change phase when the calcination temperature is too high and the calcination time is too long; the calcination temperature is too low, the calcination time is too short, and the precursor-coated lithium iron phosphate is not easy to completely decompose. The calcination temperature and the calcination time in the range are suitable, so that the source nitrogen-doped carbon-coated lithium iron phosphate can be conveniently obtained.
In summary, the present application has the following beneficial effects:
1. the lignin material in the application is widely derived from natural plant products, is large in quantity, and is low in price and renewable compared with egg yolk; in addition, the content of nitrogen introduced by the lignin can be regulated, and carbon can be doped while introducing a nitrogen source, so that the conductivity of the lithium iron phosphate is further improved; the fluidized bed coating technology of the step S5-the step S6 can improve the uniformity of source nitrogen-doped carbon coating, the coating particle size is nanometer, the coating method is simple and reliable, and large-scale production is facilitated, and the prepared source nitrogen-doped carbon lithium iron phosphate has good electrochemical performance, so that the source nitrogen-doped carbon lithium iron phosphate has good electronic conductivity and conductivity multiplying power, and has good application prospect and industrialization potential.
2. In the application, alkali lignin is preferably adopted and utilized, so that the environmental pollution can be reduced; in addition, the wheat straw alkali lignin, the bamboo pulp alkali lignin, the wood pulp alkali lignin, the enzymolysis lignin and the organic solvent extraction type lignin all contain rich nitrogen and carbon elements and can be regulated and controlled in the coating process, so that the stability and controllability of the coating effect can be improved, and the electrochemical performance and the conductivity of the lithium iron phosphate are further improved.
3. The mass ratio of the lignin material to the hydrogen peroxide is preferably 1-40, and the alkali lignin can be selected from the pulping and papermaking waste liquid, and the alkali lignin in the pulping and papermaking waste liquid has a complex structure, so that the mass ratio of the lignin to the hydrogen peroxide is 1-40, the alkali lignin can be conveniently catalyzed and oxidized by the hydrogen peroxide, the steric hindrance of methoxyl groups is eliminated, and the reaction activity of the alkali lignin is increased.
Detailed Description
The present application will be described in further detail with reference to examples.
In the examples of the present application, the drugs used are shown in table 1:
table 1 pharmaceutical products according to embodiments of the present application
Examples
Example 1
A preparation method of nitrogen-doped carbon-coated lithium iron phosphate by taking lignin as a source is characterized by comprising the following steps:
s1, preparation of demethoxylated lignin reaction liquid: dissolving 1kg of lignin material in 50kg of water, adjusting the pH to 8 by using a sodium hydroxide solution with the mass fraction of 20%, adding 0.1kg of hydrogen peroxide under the condition of 10 ℃ oil bath, stirring for 1 hour in a sealed manner, and cooling to room temperature to obtain demethoxylated lignin reaction liquid; the lignin is dealkalized lignin;
s2, preparing a diazonium salt reaction solution: dissolving 0.1kg of aniline in 5kg of water, adding 19.6% by mass of dilute sulfuric acid to adjust the pH value to 1, reacting at 0 ℃ for 10min, adding 0.1kg of sodium nitrite, and reacting at 0 ℃ for 1h to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction liquid in the step S1 with the diazonium salt reaction liquid in the step S2, adjusting the pH to 8 by using a sodium hydroxide solution with the mass fraction of 20%, stirring and reacting at 0 ℃ for 1h, adding dilute sulfuric acid with the mass fraction of 19.6% until the pH is 1, standing for 24h for natural precipitation, washing with deionized water for 3 times, and drying to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: adding 1-20kg of lignin azo polymer into 150kg of organic solvent, and stirring at normal temperature to obtain a coating precursor solution; the organic solvent is toluene;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coated precursor solution in the step S4, conveying the atomized coated precursor solution into a fluidized bed reactor in the step S5, controlling the conveying flow rate to be 30ml/h, controlling the temperature of the fluidized bed reactor to be 70 ℃, enabling the coated precursor solution to be adsorbed and deposited on the surface of the anode material, and simultaneously evaporating the solvent to dryness, controlling the mass percentage of a precursor coating layer and precursor-coated lithium iron phosphate to be 0.1%, and controlling the thickness of the precursor coating layer to be 1nm, so as to obtain precursor-coated lithium iron phosphate;
s7, calcining: calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate; the calcining temperature is 300 ℃, and the calcining time is 0.5 h.
Example 2
A preparation method of nitrogen-doped carbon-coated lithium iron phosphate by taking lignin as a source is characterized by comprising the following steps:
s1, preparation of demethoxylated lignin reaction liquid: mixing and dissolving 20kg of lignin material in 1500kg of water, adjusting the pH to 8 by using a sodium hydroxide solution with the mass fraction of 20%, adding 5kg of hydrogen peroxide under the condition of 10 ℃ oil bath, stirring for 1h in a sealed manner, and cooling to room temperature to obtain demethoxylated lignin reaction liquid; the lignin is dealkalized lignin;
s2, preparing a diazonium salt reaction solution: dissolving 5kg of aniline in 1000kg of water, adding 19.6% by mass of dilute sulfuric acid to adjust the pH value to 1, reacting at 0 ℃ for 10min, adding 5kg of sodium nitrite, and reacting at 0 ℃ for 1h to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction liquid in the step S1 with the diazonium salt reaction liquid in the step S2, adjusting the pH to 8 by using a sodium hydroxide solution with the mass fraction of 20%, stirring and reacting at 0 ℃ for 1h, adding dilute sulfuric acid with the mass fraction of 19.6% until the pH is 1, standing for 24h for natural precipitation, washing with deionized water for 3 times, and drying to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: taking 10kg of lignin azo polymer, adding the lignin azo polymer into 575kg of organic solvent, and stirring at normal temperature to obtain a coating precursor solution; the organic solvent is toluene;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coated precursor solution in the step S4, conveying the atomized coated precursor solution into a fluidized bed reactor in the step S5, controlling the conveying flow rate to be 30ml/h, controlling the temperature of the fluidized bed reactor to be 70 ℃, enabling the coated precursor solution to be adsorbed and deposited on the surface of the anode material, and simultaneously evaporating the solvent to dryness, controlling the mass percentage of a precursor coating layer and precursor-coated lithium iron phosphate to be 0.1%, and controlling the thickness of the precursor coating layer to be 1nm, so as to obtain precursor-coated lithium iron phosphate;
s7, calcining: calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate; the calcining temperature is 300 ℃, and the calcining time is 0.5 h.
Example 3
A preparation method of nitrogen-doped carbon-coated lithium iron phosphate by taking lignin as a source is characterized by comprising the following steps:
s1, preparation of demethoxylated lignin reaction liquid: mixing and dissolving 40kg of lignin material in 3000kg of water, adjusting the pH to 8 by using a sodium hydroxide solution with the mass fraction of 20%, adding 10kg of hydrogen peroxide under the condition of 10 ℃ oil bath, stirring for 1 hour in a sealed manner, and cooling to room temperature to obtain demethoxylated lignin reaction liquid; the lignin is dealkalized lignin;
s2, preparing a diazonium salt reaction solution: dissolving 10kg of aniline in 2000kg of water, adding 19.6% by mass of dilute sulfuric acid to adjust the pH value to 1, reacting at 0 ℃ for 10min, adding 10kg of sodium nitrite, and reacting at 0 ℃ for 1h to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction liquid in the step S1 with the diazonium salt reaction liquid in the step S2, adjusting the pH to 8 by using a sodium hydroxide solution with the mass fraction of 20%, stirring and reacting at 0 ℃ for 1h, adding dilute sulfuric acid with the mass fraction of 19.6% until the pH is 1, standing for 24h for natural precipitation, washing with deionized water for 3 times, and drying to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: adding 20kg of lignin azo polymer into 1000kg of organic solvent, and stirring at normal temperature to obtain a coating precursor solution; the organic solvent is toluene;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coated precursor solution in the step S4, conveying the atomized coated precursor solution into a fluidized bed reactor in the step S5, controlling the conveying flow rate to be 30ml/h, controlling the temperature of the fluidized bed reactor to be 70 ℃, enabling the coated precursor solution to be adsorbed and deposited on the surface of the anode material, and simultaneously evaporating the solvent to dryness, controlling the mass percentage of a precursor coating layer and precursor-coated lithium iron phosphate to be 0.1%, and controlling the thickness of the precursor coating layer to be 1nm, so as to obtain precursor-coated lithium iron phosphate;
s7, calcining: calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate; the calcining temperature is 300 ℃, and the calcining time is 0.5 h.
Example 4
A preparation method of nitrogen-doped carbon-coated lithium iron phosphate by taking lignin as a source is characterized by comprising the following steps:
s1, preparation of demethoxylated lignin reaction liquid: mixing and dissolving 20kg of lignin material in 1500kg of water, adjusting the pH value to 10 by using a sodium hydroxide solution with the mass fraction of 20%, adding 5kg of hydrogen peroxide under the condition of oil bath at 55 ℃, hermetically stirring for 3h, and cooling to room temperature to obtain demethoxylated lignin reaction liquid; the lignin is dealkalized lignin;
s2, preparing a diazonium salt reaction solution: dissolving 5kg of aniline in 1000kg of water, adding 19.6% by mass of dilute sulfuric acid to adjust the pH to 2, reacting at 2.5 ℃ for 25min, adding 5kg of sodium nitrite, and reacting at 2.5 ℃ for 3h to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction solution in the step S1 with the diazonium salt reaction solution in the step S2, adjusting the pH to 10 by using a sodium hydroxide solution with the mass fraction of 20%, stirring and reacting at the temperature of 2.5 ℃ for 3 hours, adding dilute sulfuric acid with the mass fraction of 19.6% until the pH is 2, standing for 24 hours for natural precipitation, washing with deionized water for 3 times, and drying to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: adding 1-20kg of lignin azo polymer into 575kg of organic solvent, and stirring at normal temperature to obtain a coating precursor solution; the organic solvent is toluene;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coated precursor solution in the step S4, conveying the atomized coated precursor solution into a fluidized bed reactor in the step S5, controlling the conveying flow rate to be 30ml/h, controlling the temperature of the fluidized bed reactor to be 100 ℃, enabling the coated precursor solution to be adsorbed and deposited on the surface of the anode material, and simultaneously evaporating the solvent to dryness, controlling the mass percentage of a precursor coating layer and precursor-coated lithium iron phosphate to be 0.1%, and controlling the thickness of the precursor coating layer to be 1nm, so as to obtain precursor-coated lithium iron phosphate;
s7, calcining: calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate; the calcining temperature is 300 ℃, and the calcining time is 0.5 h.
Example 5
A preparation method of nitrogen-doped carbon-coated lithium iron phosphate by taking lignin as a source is characterized by comprising the following steps:
s1, preparation of demethoxylated lignin reaction liquid: mixing and dissolving 20kg of lignin material in 1500kg of water, adjusting the pH to 12 by using a sodium hydroxide solution with the mass fraction of 20%, adding 5kg of hydrogen peroxide under the condition of 100 ℃ oil bath, stirring for 5 hours in a sealed manner, and cooling to room temperature to obtain demethoxylated lignin reaction liquid; the lignin is dealkalized lignin;
s2, preparing a diazonium salt reaction solution: dissolving 5kg of aniline in 1000kg of water, adding 19.6% by mass of dilute sulfuric acid to adjust the pH value to 3, reacting at 5 ℃ for 40min, adding 5kg of sodium nitrite, and reacting at 5 ℃ for 5h to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction liquid in the step S1 with the diazonium salt reaction liquid in the step S2, adjusting the pH to 12 by using a sodium hydroxide solution with the mass fraction of 20%, stirring and reacting at 5 ℃ for 5 hours, adding dilute sulfuric acid with the mass fraction of 19.6% until the pH is 1-3, standing for 24 hours for natural precipitation, washing with deionized water for 3 times, and drying to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: adding 1-20kg of lignin azo polymer into 575kg of organic solvent, and stirring at normal temperature to obtain a coating precursor solution; the organic solvent is toluene;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coated precursor solution in the step S4, conveying the atomized coated precursor solution into a fluidized bed reactor in the step S5, controlling the conveying flow rate to be 30ml/h, controlling the temperature of the fluidized bed reactor to be 130 ℃, enabling the coated precursor solution to be adsorbed and deposited on the surface of the anode material, and simultaneously evaporating the solvent to dryness, controlling the mass percentage of a precursor coating layer and precursor-coated lithium iron phosphate to be 0.1%, and controlling the thickness of the precursor coating layer to be 1nm, so as to obtain precursor-coated lithium iron phosphate;
s7, calcining: calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate; the calcining temperature is 300 ℃, and the calcining time is 0.5 h.
Examples 6 to 11
Examples 6-11 differ from example 4 in the choice of lignin material as shown below:
the lignin material in step S1 of example 7 was bamboo pulp alkali lignin;
the lignin material in step S1 of example 8 was wood pulp alkali lignin;
the lignin material in step S1 of example 9 is enzymatically hydrolyzed lignin;
the lignin material in step S1 of example 10 is an organic solvent-extracted lignin;
the lignin material in step S1 of example 11 was bamboo pulp alkali lignin and wood pulp alkali lignin mixed in a mass ratio of 1: 1.
The lignin materials of examples 7-11 were all extracted from pulp and paper mill effluents.
Examples 12 to 16
Examples 12 to 16 differ from example 11 in the mass ratio of the lignin material to the hydrogen peroxide in step S1, as follows:
in example 12, 10kg of the lignin material and 10kg of hydrogen peroxide were used, and the mass ratio of the lignin material to the hydrogen peroxide was 1;
in example 13, 20kg of the lignin material, 1kg of hydrogen peroxide and a mass ratio of the lignin material to the hydrogen peroxide were 20;
in example 14, the weight ratio of the lignin material was 40kg, the weight ratio of the hydrogen peroxide was 1kg, and the weight ratio of the lignin material to the hydrogen peroxide was 40;
in example 15, the weight ratio of the lignin material was 5kg, the weight ratio of the hydrogen peroxide was 10kg, and the weight ratio of the lignin material to the hydrogen peroxide was 0.5;
in example 16, 30kg of the lignin material, 0.5kg of hydrogen peroxide and the mass ratio of the lignin material to the hydrogen peroxide were 60.
Examples 17 to 20
Examples 17-20 differ from example 13 in that examples 17-20 employ an aniline derivative in place of the aniline of step S2 of example 13 as follows:
the aniline derivative in example 17 was p-nitroaniline;
the aniline derivative in example 18 is p-aminobenzoic acid;
the aniline derivative in example 19 is ethyl p-aminobenzoate;
the aniline derivative in example 20 was p-anisidine.
Examples 21 to 24
Examples 21 to 24 are different from example 17 in that the organic solvent used in step S3 is different as follows:
the organic solvent in example 21 was tetrahydrofuran;
the organic solvent in example 22 was dimethyl sulfoxide;
the organic solvent in example 23 was dimethylformamide;
the organic solvent in example 24 is dioxane.
Examples 25 to 28
The difference between the embodiments 25 to 28 and 21 is that the mass percentages of the precursor coating layer and the precursor-coated lithium iron phosphate in step S6 and the thickness of the precursor coating layer are different, as shown in the following:
in the embodiment 25, the mass percentage of the precursor coating layer to the precursor-coated lithium iron phosphate is 0.2%, and the thickness of the precursor coating layer is 2 nm;
in the embodiment 26, the mass percentage of the precursor coating layer to the precursor-coated lithium iron phosphate is 2.6%, and the thickness of the precursor coating layer is 26 nm;
in the embodiment 27, the mass percentage of the precursor coating layer to the precursor-coated lithium iron phosphate is 5%, and the thickness of the precursor coating layer is 50 nm;
in example 28, the mass percentage of the precursor coating layer to the precursor-coated lithium iron phosphate is 6%, and the thickness of the precursor coating layer is 60 nm.
Examples 29 to 32
Examples 29 to 32 differ from example 26 in that the flow rates of the delivery of the coating precursor solutions in step S6 differ as follows:
the flow rate of delivery of the coating precursor solution in example 29 was 50 mL/h;
the flow rate of delivery of the coating precursor solution in example 30 was 75 mL/h;
in the embodiment 31, the flow rate of the delivery of the coating precursor solution is 100 mL/h;
the flow rate for delivery of the coating precursor solution in example 32 was 120 mL/h.
Examples 33 to 36
Examples 33 to 36 differ from example 30 in the temperature and calcination time of the calcination treatment in step S7, as follows:
the temperature of the calcination treatment in example 33 was 550 ℃ and the calcination time was 2 hours;
the temperature of the calcination treatment in example 34 was 675 ℃ and the calcination time was 7 hours;
the temperature of the calcination treatment in example 35 was 900 ℃ and the calcination time was 12 hours;
the calcination treatment in example 36 was carried out at 1150 ℃ for 13.5 hours.
Comparative example
Comparative example 1
The difference between this comparative example and example 2 is that the egg yolk was used in this comparative example instead of the lignin material of example 2, the yolk reaction solution was obtained in step 1, and the demethoxylated lignin reaction solution was replaced with the yolk reaction solution in the subsequent step.
Comparative example 2
This comparative example differs from example 2 in that it employs, instead of S5-S6 in example 2, the step S (alternative) of:
adding lithium iron phosphate, the coated precursor solution, zirconium beads and deionized water into a ball mill, and mixing and ball-milling for 1h at 70 ℃ to obtain precursor-coated lithium iron phosphate.
Performance test
Testing of electrochemical Performance
And preparing the prepared source nitrogen-doped carbon-coated lithium iron phosphate into the positive pole piece of the lithium ion button cell by adopting a slurry coating method. The specific operation is that the active component (ternary anode material), the conductive agent Super-Pcarbon and the binder NMP are mixed according to the mass ratio of 94:3:3, then the mixture is evenly coated on an aluminum foil, and after vacuum drying at 120 ℃, the mixture is compacted under 10Mpa to obtain the electrode plate.
Taking an electrode pole piece as a working electrode, taking metal lithium as a reference electrode, and taking Celgard2400 as a diaphragm; mixing EC/DEC/DMC according to the volume ratio of 1:1:1 to obtain a mixed solution, and mixing the mixed solution and 1mol/L lithium hexafluorophosphate according to the volume ratio of 3:1 to prepare an electrolyte. Assembling into a CR2032 button cell, and testing the constant-current charge-discharge performance on a cell testing system at the test temperature of 25 ℃.
TABLE 2 Performance test Table
Examples 1 to 3 were compared, and examples 1 to 3 were different in the ratio of raw materials in which lignin was used as the source nitrogen-doped carbon-coated lithium iron phosphate, and since example 2 had the maximum charge capacity and discharge capacity, the conductivity of example 2 was the best, and the ratio of raw materials in example 2 was the best.
Comparing examples 4 to 5 with example 2, examples 4 to 5 were different from example 2 in the preparation process conditions of the lithium iron phosphate having lignin as a source nitrogen-doped carbon coating, and since example 4 has the maximum charge capacity and discharge capacity, the conductivity of example 2 was the best, which illustrates the best process conditions for preparing the lithium iron phosphate having lignin as a source nitrogen-doped carbon coating in example 4.
Comparing examples 6-11 with example 4, examples 6-11 differ from example 4 in the choice of lignin material, and since examples 6-11 have both a higher charge capacity and discharge capacity than example 4, examples 6-11 have a higher conductivity than example 4, indicating that the lignin material in this application is better. In addition, the charge capacity and the discharge capacity of the example 11 are both larger than those of the examples 6 to 10, so that the conductivity of the example 11 is larger than that of the examples 6 to 10, which shows that the multicomponent lignin material is better.
Comparing examples 12-14 with examples 15-16, examples 12-14 differ from examples 15-16 in the mass ratio of lignin material to hydrogen peroxide, and since examples 12-14 have both a higher charge capacity and discharge capacity than examples 15-16, the conductivity of examples 12-14 is greater than that of examples 15-16, indicating that the mass ratio of lignin material to hydrogen peroxide in this application is better. In examples 12 to 14, the charge capacity and the discharge capacity of example 13 were the largest, and therefore the conductivity of example 13 was the best, indicating that the mass ratio of the lignin material to the hydrogen peroxide was the best in example 13.
Comparing examples 17-20 with example 13, examples 17-20 differ from example 13 in that examples 17-20 employ aniline derivatives in place of the aniline in step S2 of example 13, and since examples 17-20 have both greater charge and discharge capacities than example 13, the conductivity of examples 17-20 is greater than that of example 13, indicating that the aniline derivatives in this application are superior to aniline. In addition, the charge capacity and discharge capacity of example 17 were both greater than those of examples 18 to 20, and therefore the conductivity of example 17 was greater than those of examples 18 to 20, indicating that the aniline derivative of example 17 was the best.
Comparing examples 21-24 with example 17, examples 21-24 differ from example 17 in the organic solvent selected in step S3, and since examples 21-24 both had a larger charge capacity and discharge capacity than example 17, the conductivity of examples 21-24 was greater than that of example 17, indicating that the organic solvent selected in step S3 in this application is more preferred. In addition, the charge capacity and the discharge capacity of example 21 were both larger than those of examples 22 to 24, and therefore the conductivity of example 21 was larger than those of examples 22 to 24, indicating that the organic solvent selected in step S3 of example 21 was the best.
Comparing examples 25 to 27 with examples 21 and 28, examples 25 to 27 are different from examples 21 and 28 in the mass percentages of the precursor coating layer and the precursor-coated lithium iron phosphate and the thickness of the precursor coating layer in step S6, and since examples 25 to 27 are both larger in charge capacity and discharge capacity than examples 21 and 28, the electrical conductivities of examples 25 to 27 are larger than those of examples 21 and 28, which indicates that the mass percentages of the precursor coating layer and the precursor-coated lithium iron phosphate and the thickness of the precursor coating layer in step S6 in this application are more preferable. In examples 25 to 27, since the charge capacity and the discharge capacity of example 26 were both larger than those of examples 25 and 27, the conductivity of example 26 was larger than those of examples 25 and 27, and it was explained that the mass percentages of the precursor coating layer and the precursor-coated lithium iron phosphate and the thickness of the precursor coating layer were the best in step S6 in example 26.
Comparing examples 29 to 31 with examples 26 and 32, examples 29 to 31 differ from examples 26 and 32 in that the flow rate of delivery of the coating precursor solution in step S6 is different, and since examples 29 to 31 have a larger charge capacity and discharge capacity than examples 26 and 32, the conductivity of examples 29 to 31 is higher than that of examples 26 and 32, which indicates that the flow rate of delivery of the coating precursor solution in step S6 in the present application is better. In examples 29 to 31, since the charge capacity and the discharge capacity of example 30 were both larger than those of examples 29 and 31, the conductivity of example 30 was larger than those of examples 29 and 31, and it was found that the flow rate of the coating precursor solution supplied in step S6 was the best in example 30.
Comparing examples 33 to 35 with examples 30 and 36, examples 33 to 35 are different from examples 30 and 36 in the temperature and the calcination time of the calcination treatment in step S7, and since examples 33 to 35 have a larger charge capacity and a larger discharge capacity than examples 30 and 36, the conductivity of examples 33 to 35 is higher than that of examples 30 and 36, which indicates that the temperature and the calcination time of the calcination treatment in step S7 are better. In examples 33 to 35, since the charge capacity and the discharge capacity of example 34 were both larger than those of examples 33 and 35, the conductivity of example 33 was larger than those of examples 33 and 35, and it was found that the temperature and the calcination time of the calcination treatment in step S7 were the best in example 34.
Finally, comparative examples 1-2 were compared to example 2, and comparative examples 1-2 differed from example 1 in that comparative example 1 used egg yolk instead of the lignin material of example 2; comparative example 2 employs, instead of S5-S6 in example 2, step S (alternative) of: adding lithium iron phosphate, the coated precursor solution, zirconium beads and deionized water into a ball mill, and mixing and ball-milling for 1h at 70 ℃ to obtain precursor-coated lithium iron phosphate. Since example 2 has the largest charge capacity and discharge capacity, example 2 has a higher conductivity, indicating that the scheme of the present application is better.
The present embodiment is only for explaining the present application, and it is not limited to the present application, and those skilled in the art can make modifications of the present embodiment without inventive contribution as needed after reading the present specification, but all of them are protected by patent law within the scope of the claims of the present application.
Claims (9)
1. A preparation method of nitrogen-doped carbon-coated lithium iron phosphate by taking lignin as a source is characterized by comprising the following steps:
s1, preparation of demethoxylated lignin reaction liquid: mixing 1-40 parts by weight of lignin material and 50-3000 parts by weight of water, adjusting the pH to 8-12, adding 0.1-10 parts by weight of hydrogen peroxide at 10-100 ℃, mixing and stirring for 1-5h, and cooling to room temperature to obtain demethoxylated lignin reaction liquid;
s2, preparing a diazonium salt reaction solution: according to the weight portion, 0.1-10 portions of aniline or aniline derivatives and 5-2000 portions of water are stirred and mixed, inorganic acid is added, the pH value is adjusted to 1-3, and the mixture reacts for 10-40min at the temperature of 0-5 ℃ to obtain a first reaction liquid; stirring and mixing the first reaction solution and 0.1-10 parts of sodium nitrite, and reacting for 1-5h at 0-5 ℃ to obtain a diazonium salt reaction solution;
s3, mixing reaction: mixing the demethoxylated lignin reaction liquid obtained in the step S1 and the diazonium salt reaction liquid obtained in the step S2 in parts by weight, adjusting the pH to 8-12, stirring and reacting at 0-5 ℃ for 1-5 hours, and adding inorganic acid to adjust the pH to 1-3 to obtain a second reaction liquid; standing, precipitating, washing and drying the second reaction solution to obtain a lignin azo polymer;
s4, preparing a coating precursor solution: mixing 1-20 parts by weight of lignin azo polymer and 1000 parts by weight of organic solvent, and stirring at normal temperature to obtain a coating precursor solution;
s5, suspending lithium iron phosphate: suspending lithium iron phosphate in a fluidized bed reactor by a carrier gas;
s6, preparing precursor-coated lithium iron phosphate: atomizing the coating precursor solution in the step S4, conveying the atomized coating precursor solution to the fluidized bed reactor in the step S5, controlling the temperature of the fluidized bed reactor to be 70-130 ℃, so that the coating precursor solution is adsorbed and deposited on the surface of the anode material, and simultaneously evaporating the solvent to dryness to obtain precursor-coated lithium iron phosphate;
s7, calcining: and calcining the precursor-coated lithium iron phosphate to obtain source nitrogen-doped carbon-coated lithium iron phosphate.
2. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: in step S1, the lignin material is alkali lignin, and the alkali lignin includes one or more of wheat straw alkali lignin, bamboo pulp alkali lignin, wood pulp alkali lignin, enzymatic hydrolysis lignin, and organic solvent extraction type lignin.
3. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 2, wherein the method comprises the following steps: the mass ratio of the lignin material to the hydrogen peroxide in step S1 is 1 to 40.
4. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: the molar ratio of the aniline or aniline derivative to the sodium nitrite in the step S2 is controlled to be 0.8-1.5.
5. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: the aniline derivative in step S2 is any one of p-nitroaniline, p-aminobenzoic acid, ethyl p-aminobenzoate, and p-anisidine.
6. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: in step S3, the organic solvent is any one of tetrahydrofuran, dimethyl sulfoxide, dimethylformamide and dioxane.
7. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: in the precursor-coated lithium iron phosphate obtained in step S6, the mass percentage of the precursor coating layer to the precursor-coated lithium iron phosphate is 0.2% to 5%, and the thickness of the precursor coating layer is 2nm to 50 nm.
8. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: the flow rate of the delivery of the coating precursor solution in step S6 is 50-100 mL/h.
9. The preparation method of nitrogen-doped carbon-coated lithium iron phosphate by using lignin as a source according to claim 1, wherein the method comprises the following steps: the temperature of the calcination treatment in the step S7 is 550-900 ℃, and the calcination time is 2-12 h.
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