CN111606314B - Preparation method of sodium ion battery anode material sodium vanadium trifluorophosphate - Google Patents
Preparation method of sodium ion battery anode material sodium vanadium trifluorophosphate Download PDFInfo
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- 229910001415 sodium ion Inorganic materials 0.000 title claims abstract description 69
- FKNQFGJONOIPTF-UHFFFAOYSA-N Sodium cation Chemical compound [Na+] FKNQFGJONOIPTF-UHFFFAOYSA-N 0.000 title claims abstract description 68
- -1 sodium vanadium trifluorophosphate Chemical compound 0.000 title claims abstract description 67
- 239000010405 anode material Substances 0.000 title claims abstract description 31
- 238000002360 preparation method Methods 0.000 title claims abstract description 15
- 238000010438 heat treatment Methods 0.000 claims abstract description 36
- 239000011734 sodium Substances 0.000 claims abstract description 36
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 claims abstract description 30
- 229910052799 carbon Inorganic materials 0.000 claims abstract description 30
- 238000000034 method Methods 0.000 claims abstract description 26
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims abstract description 20
- YCKRFDGAMUMZLT-UHFFFAOYSA-N Fluorine atom Chemical compound [F] YCKRFDGAMUMZLT-UHFFFAOYSA-N 0.000 claims abstract description 18
- 229910052731 fluorine Inorganic materials 0.000 claims abstract description 18
- 239000011737 fluorine Substances 0.000 claims abstract description 18
- 239000002243 precursor Substances 0.000 claims abstract description 14
- 239000002994 raw material Substances 0.000 claims abstract description 13
- DGAQECJNVWCQMB-PUAWFVPOSA-M Ilexoside XXIX Chemical compound C[C@@H]1CC[C@@]2(CC[C@@]3(C(=CC[C@H]4[C@]3(CC[C@@H]5[C@@]4(CC[C@@H](C5(C)C)OS(=O)(=O)[O-])C)C)[C@@H]2[C@]1(C)O)C)C(=O)O[C@H]6[C@@H]([C@H]([C@@H]([C@H](O6)CO)O)O)O.[Na+] DGAQECJNVWCQMB-PUAWFVPOSA-M 0.000 claims abstract description 11
- 229910052708 sodium Inorganic materials 0.000 claims abstract description 11
- 238000001291 vacuum drying Methods 0.000 claims abstract description 10
- 229910052720 vanadium Inorganic materials 0.000 claims abstract description 10
- LEONUFNNVUYDNQ-UHFFFAOYSA-N vanadium atom Chemical compound [V] LEONUFNNVUYDNQ-UHFFFAOYSA-N 0.000 claims abstract description 10
- OAICVXFJPJFONN-UHFFFAOYSA-N Phosphorus Chemical compound [P] OAICVXFJPJFONN-UHFFFAOYSA-N 0.000 claims abstract description 9
- 229910052698 phosphorus Inorganic materials 0.000 claims abstract description 9
- 239000011574 phosphorus Substances 0.000 claims abstract description 9
- 238000001816 cooling Methods 0.000 claims abstract description 7
- 238000000227 grinding Methods 0.000 claims abstract description 4
- 238000003756 stirring Methods 0.000 claims description 30
- KRKNYBCHXYNGOX-UHFFFAOYSA-N citric acid Chemical compound OC(=O)CC(O)(C(O)=O)CC(O)=O KRKNYBCHXYNGOX-UHFFFAOYSA-N 0.000 claims description 28
- 239000000203 mixture Substances 0.000 claims description 19
- XKRFYHLGVUSROY-UHFFFAOYSA-N Argon Chemical compound [Ar] XKRFYHLGVUSROY-UHFFFAOYSA-N 0.000 claims description 16
- PUZPDOWCWNUUKD-UHFFFAOYSA-M sodium fluoride Chemical compound [F-].[Na+] PUZPDOWCWNUUKD-UHFFFAOYSA-M 0.000 claims description 16
- GNTDGMZSJNCJKK-UHFFFAOYSA-N divanadium pentaoxide Chemical compound O=[V](=O)O[V](=O)=O GNTDGMZSJNCJKK-UHFFFAOYSA-N 0.000 claims description 14
- 238000001035 drying Methods 0.000 claims description 13
- 238000005303 weighing Methods 0.000 claims description 11
- 229910052786 argon Inorganic materials 0.000 claims description 9
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- 150000007524 organic acids Chemical group 0.000 claims description 8
- 239000011775 sodium fluoride Substances 0.000 claims description 8
- 235000013024 sodium fluoride Nutrition 0.000 claims description 8
- VHUUQVKOLVNVRT-UHFFFAOYSA-N Ammonium hydroxide Chemical compound [NH4+].[OH-] VHUUQVKOLVNVRT-UHFFFAOYSA-N 0.000 claims description 7
- 235000011114 ammonium hydroxide Nutrition 0.000 claims description 7
- YASYEJJMZJALEJ-UHFFFAOYSA-N Citric acid monohydrate Chemical compound O.OC(=O)CC(O)(C(O)=O)CC(O)=O YASYEJJMZJALEJ-UHFFFAOYSA-N 0.000 claims description 6
- LFVGISIMTYGQHF-UHFFFAOYSA-N ammonium dihydrogen phosphate Chemical compound [NH4+].OP(O)([O-])=O LFVGISIMTYGQHF-UHFFFAOYSA-N 0.000 claims description 6
- 229910000387 ammonium dihydrogen phosphate Inorganic materials 0.000 claims description 6
- 229960002303 citric acid monohydrate Drugs 0.000 claims description 6
- 235000019837 monoammonium phosphate Nutrition 0.000 claims description 6
- 239000006012 monoammonium phosphate Substances 0.000 claims description 6
- CDBYLPFSWZWCQE-UHFFFAOYSA-L sodium carbonate Substances [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 claims description 6
- 230000002378 acidificating effect Effects 0.000 claims description 5
- 150000003863 ammonium salts Chemical class 0.000 claims description 5
- 238000000498 ball milling Methods 0.000 claims description 5
- MNNHAPBLZZVQHP-UHFFFAOYSA-N diammonium hydrogen phosphate Chemical compound [NH4+].[NH4+].OP([O-])([O-])=O MNNHAPBLZZVQHP-UHFFFAOYSA-N 0.000 claims description 5
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 4
- JJEJDZONIFQNHG-UHFFFAOYSA-N [C+4].N Chemical compound [C+4].N JJEJDZONIFQNHG-UHFFFAOYSA-N 0.000 claims description 4
- VWDWKYIASSYTQR-UHFFFAOYSA-N sodium nitrate Chemical compound [Na+].[O-][N+]([O-])=O VWDWKYIASSYTQR-UHFFFAOYSA-N 0.000 claims description 4
- DDFHBQSCUXNBSA-UHFFFAOYSA-N 5-(5-carboxythiophen-2-yl)thiophene-2-carboxylic acid Chemical group S1C(C(=O)O)=CC=C1C1=CC=C(C(O)=O)S1 DDFHBQSCUXNBSA-UHFFFAOYSA-N 0.000 claims description 3
- 239000005696 Diammonium phosphate Substances 0.000 claims description 3
- 229910000388 diammonium phosphate Inorganic materials 0.000 claims description 3
- 235000019838 diammonium phosphate Nutrition 0.000 claims description 3
- 238000002156 mixing Methods 0.000 claims description 3
- 229910000029 sodium carbonate Inorganic materials 0.000 claims description 3
- YWYZEGXAUVWDED-UHFFFAOYSA-N triammonium citrate Chemical compound [NH4+].[NH4+].[NH4+].[O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O YWYZEGXAUVWDED-UHFFFAOYSA-N 0.000 claims description 3
- QGZKDVFQNNGYKY-UHFFFAOYSA-O Ammonium Chemical compound [NH4+] QGZKDVFQNNGYKY-UHFFFAOYSA-O 0.000 claims description 2
- 239000004254 Ammonium phosphate Substances 0.000 claims description 2
- KRKNYBCHXYNGOX-UHFFFAOYSA-K Citrate Chemical compound [O-]C(=O)CC(O)(CC([O-])=O)C([O-])=O KRKNYBCHXYNGOX-UHFFFAOYSA-K 0.000 claims description 2
- VMHLLURERBWHNL-UHFFFAOYSA-M Sodium acetate Chemical compound [Na+].CC([O-])=O VMHLLURERBWHNL-UHFFFAOYSA-M 0.000 claims description 2
- 229910000148 ammonium phosphate Inorganic materials 0.000 claims description 2
- 235000019289 ammonium phosphates Nutrition 0.000 claims description 2
- BWKOZPVPARTQIV-UHFFFAOYSA-N azanium;hydron;2-hydroxypropane-1,2,3-tricarboxylate Chemical compound [NH4+].OC(=O)CC(O)(C(O)=O)CC([O-])=O BWKOZPVPARTQIV-UHFFFAOYSA-N 0.000 claims description 2
- UNTBPXHCXVWYOI-UHFFFAOYSA-O azanium;oxido(dioxo)vanadium Chemical compound [NH4+].[O-][V](=O)=O UNTBPXHCXVWYOI-UHFFFAOYSA-O 0.000 claims description 2
- KLOIYEQEVSIOOO-UHFFFAOYSA-N carbocromen Chemical compound CC1=C(CCN(CC)CC)C(=O)OC2=CC(OCC(=O)OCC)=CC=C21 KLOIYEQEVSIOOO-UHFFFAOYSA-N 0.000 claims description 2
- 239000007789 gas Substances 0.000 claims description 2
- 229910052757 nitrogen Inorganic materials 0.000 claims description 2
- OGUCKKLSDGRKSH-UHFFFAOYSA-N oxalic acid oxovanadium Chemical compound [V].[O].C(C(=O)O)(=O)O OGUCKKLSDGRKSH-UHFFFAOYSA-N 0.000 claims description 2
- 230000001105 regulatory effect Effects 0.000 claims description 2
- 239000001632 sodium acetate Substances 0.000 claims description 2
- 235000017281 sodium acetate Nutrition 0.000 claims description 2
- 235000017550 sodium carbonate Nutrition 0.000 claims description 2
- 239000004317 sodium nitrate Substances 0.000 claims description 2
- 235000010344 sodium nitrate Nutrition 0.000 claims description 2
- 239000001393 triammonium citrate Substances 0.000 claims description 2
- 235000011046 triammonium citrate Nutrition 0.000 claims description 2
- 239000007774 positive electrode material Substances 0.000 abstract description 31
- 230000015572 biosynthetic process Effects 0.000 abstract description 11
- 239000000463 material Substances 0.000 abstract description 11
- 238000003786 synthesis reaction Methods 0.000 abstract description 10
- 239000012535 impurity Substances 0.000 abstract description 3
- 230000000052 comparative effect Effects 0.000 description 30
- 239000007788 liquid Substances 0.000 description 30
- 229910001373 Na3V2(PO4)2F3 Inorganic materials 0.000 description 10
- 239000010406 cathode material Substances 0.000 description 8
- 229960004106 citric acid Drugs 0.000 description 8
- 230000008569 process Effects 0.000 description 8
- 230000014759 maintenance of location Effects 0.000 description 7
- 239000012071 phase Substances 0.000 description 6
- 239000007787 solid Substances 0.000 description 6
- 238000002441 X-ray diffraction Methods 0.000 description 5
- ZMVMBTZRIMAUPN-UHFFFAOYSA-H [Na+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O Chemical compound [Na+].[V+5].[O-]P([O-])([O-])=O.[O-]P([O-])([O-])=O ZMVMBTZRIMAUPN-UHFFFAOYSA-H 0.000 description 5
- 239000000725 suspension Substances 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 3
- 230000003139 buffering effect Effects 0.000 description 3
- 230000001276 controlling effect Effects 0.000 description 3
- 238000004146 energy storage Methods 0.000 description 3
- 238000010304 firing Methods 0.000 description 3
- 229910052744 lithium Inorganic materials 0.000 description 3
- 229910001416 lithium ion Inorganic materials 0.000 description 3
- 238000012544 monitoring process Methods 0.000 description 3
- 238000011056 performance test Methods 0.000 description 3
- 238000011160 research Methods 0.000 description 3
- 238000001228 spectrum Methods 0.000 description 3
- 239000002253 acid Substances 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 2
- 238000006243 chemical reaction Methods 0.000 description 2
- 238000011161 development Methods 0.000 description 2
- 239000000126 substance Substances 0.000 description 2
- QGZKDVFQNNGYKY-UHFFFAOYSA-N ammonia Natural products N QGZKDVFQNNGYKY-UHFFFAOYSA-N 0.000 description 1
- 229960004543 anhydrous citric acid Drugs 0.000 description 1
- 239000003054 catalyst Substances 0.000 description 1
- 230000008859 change Effects 0.000 description 1
- 239000002738 chelating agent Substances 0.000 description 1
- 239000003638 chemical reducing agent Substances 0.000 description 1
- 239000011248 coating agent Substances 0.000 description 1
- 238000000576 coating method Methods 0.000 description 1
- 238000010668 complexation reaction Methods 0.000 description 1
- 230000001351 cycling effect Effects 0.000 description 1
- 238000009792 diffusion process Methods 0.000 description 1
- 238000004090 dissolution Methods 0.000 description 1
- 238000005516 engineering process Methods 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 125000005842 heteroatom Chemical group 0.000 description 1
- 230000007062 hydrolysis Effects 0.000 description 1
- 238000006460 hydrolysis reaction Methods 0.000 description 1
- 230000006872 improvement Effects 0.000 description 1
- 238000004519 manufacturing process Methods 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 238000010979 pH adjustment Methods 0.000 description 1
- 239000006179 pH buffering agent Substances 0.000 description 1
- 229920000447 polyanionic polymer Polymers 0.000 description 1
- 230000001737 promoting effect Effects 0.000 description 1
- 238000006722 reduction reaction Methods 0.000 description 1
- 238000012827 research and development Methods 0.000 description 1
- 230000000630 rising effect Effects 0.000 description 1
- 238000005245 sintering Methods 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 239000007790 solid phase Substances 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 239000011232 storage material Substances 0.000 description 1
- 238000001308 synthesis method Methods 0.000 description 1
- 238000010189 synthetic method Methods 0.000 description 1
- 150000003682 vanadium compounds Chemical class 0.000 description 1
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- 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
- C01B25/455—Phosphates containing halogen
-
- 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
-
- 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
- H01M10/054—Accumulators with insertion or intercalation of metals other than lithium, e.g. with magnesium or aluminium
-
- 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
- H01M4/582—Halogenides
-
- 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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- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2002/00—Crystal-structural characteristics
- C01P2002/70—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data
- C01P2002/72—Crystal-structural characteristics defined by measured X-ray, neutron or electron diffraction data by d-values or two theta-values, e.g. as X-ray diagram
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- 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
A preparation method of sodium ion battery anode material sodium vanadium trifluorophosphate belongs to the technical field of battery material synthesis. The preparation method comprises the following steps: (1) Dissolving raw materials such as a carbon source, a vanadium source, a phosphorus source, a fluorine source, a sodium source and the like; (2) removing free water under heating to obtain wet sol; (3) carrying out vacuum drying on the wet sol to obtain xerogel; (4) grinding the xerogel to obtain a powdery precursor; (5) Under the protection of flowing inert atmosphere, presintering and roasting the precursor, and cooling along with a furnace. The sodium ion battery anode material sodium vanadium trifluorophosphate prepared by the invention has high purity, and eliminates 3.3V (vs. Na) caused by impurity phase + and/Na), and the working voltage and energy density of the positive electrode material are improved. The method is simple to operate and good in reproducibility, and the prepared material has higher energy density and excellent multiplying power and cycle performance, and can meet the actual application requirement of the sodium ion battery.
Description
Technical Field
The invention belongs to the technical field of battery material synthesis, and particularly relates to a preparation method of sodium ion battery anode material sodium vanadium trifluorophosphate.
Background
Lithium ion batteries have been an ideal power source for portable electronic devices such as mobile phones, portable computers, and high-quality cameras because of their high operating voltage, high energy density, and low environmental pollution. With the rising of the electric automobile industry, the demand of lithium resources on lithium ion batteries in the market is rapidly increased, and the price of the lithium ion batteries is continuously increased. While the lithium reserves are limited, in the near future, there is a need for lithium resource exhaustion and price rise. Therefore, development of efficient energy storage materials and devices with abundant resources, low price, high safety and long service life is urgent.
In contrast, sodium element is low in price and abundant in reserves, and research and development and application of sodium ion batteries are beneficial to promoting development and innovation of large-scale energy storage technologies, so that sodium ion batteries gradually become research hotspots in the energy storage field. Compositionally, the positive electrode material is a critical part of a sodium ion battery, which largely determines the electrochemical properties of the overall battery system, such as capacity, operating voltage, cycle life, etc. In the research of the prior sodium ion battery anode material, the polyanion compound sodium vanadium trifluorophosphate (the chemical formula is Na 3 V 2 (PO 4 ) 2 F 3 ) Because of the open three-dimensional framework structure, the cathode material has more sodium storage vacancies and unobstructed sodium ion diffusion channels, so that the cathode material has higher specific capacity and better cycling stability when being used as a cathode material of a sodium ion battery. And, due to the introduction of fluorine element, the average operating voltage of sodium vanadium trifluorophosphate is higher than that of sodium vanadium phosphate (formula Na 3 V 2 (PO 4 ) 3 ) An improvement of about 300mV is obtained, which makes the sodium vanadium trifluorophosphate have great application prospect in the cathode material of commercial sodium ion batteries, and therefore, the sodium vanadium trifluorophosphate is also widely paid attention to.
Although sodium ion battery positive electrode material sodium vanadium trifluorophosphate has the advantages, most of research and report on the preparation of sodium vanadium trifluorophosphate samples contain mixed phases such as sodium vanadium phosphate and other vanadium compounds. The presence of these hetero-phases will on the one hand directly reduce the positive electrode materialOn the other hand, the average operating voltage that can be exhibited by the positive electrode is reduced to some extent, thereby reducing the energy density of the battery. Most literature reports that the sodium vanadium trifluorophosphate sample prepared by the method shows 3.6V (vs Na + about/Na) and 4.1V (vs.Na + Besides the two discharge voltage plateaus around/Na), 3.3V (vs. Na) + Na), which is the manifestation of the heterogeneous sodium vanadium phosphate. In addition, although some documents prepare purer sodium vanadium trifluorophosphate samples, a low-voltage discharge platform of about 3.3V in a charge-discharge curve cannot be completely eliminated, and the corresponding material synthesis method and manufacturing flow are often complex. Therefore, for the purpose of realizing higher energy density and better performance, a synthetic method which is easy to operate is needed to prepare sodium ion battery anode material sodium vanadium trifluorophosphate.
Disclosure of Invention
The invention aims to solve the problems of reduced battery working voltage and energy density, poor cycle stability and the like caused by the generation of heterogeneous sodium vanadium phosphate due to volatilization of fluorine element in the preparation process of sodium ion battery positive electrode material sodium vanadium trifluorophosphate, and provides a preparation method of sodium ion battery positive electrode material sodium vanadium trifluorophosphate, which simplifies the preparation process, is convenient for practical operation, and eliminates 3.3V (vs.Na) caused by heterogeneous phase by controlling a synthesis process + Na) low operating voltage plateau.
In order to achieve the above purpose, the technical scheme adopted by the invention is as follows:
the preparation method of the sodium ion battery anode material sodium vanadium trifluorophosphate comprises the following steps:
step one: at room temperature, dissolving a carbon source in deionized water, and stirring and mixing uniformly to obtain a clear solution M 1 Regulate M 1 Is weakly acidic;
step two: weighing the raw materials and taking the raw materials and the total carbon source as a molar ratio of 5:2, adding it to solution M 1 In the process, a clear solution M is obtained after stirring and heating conditions are maintained for 20 to 30 minutes 2 ；
Step three: weighing scaleAdding a phosphorus source, a sodium source and a fluorine source into the solution M 2 In the process, stirring and heating conditions are kept for 10 to 15 minutes to obtain a clear solution M 3 ；
Step four: the stirring and heating conditions are kept unchanged, so that the solution M 3 The water in the solution M is evaporated continuously after 8 to 12 hours 3 Gradually changing into black sol to finally form gel P 1 ；
Step five: transferring the gel in the fourth step into a vacuum drying oven, vacuumizing, heating and drying to obtain xerogel P after the completion of the drying 2 ；
Step six: taking out the xerogel in the step five, grinding with a pestle or ball milling to obtain a powdery precursor, then placing the powdery precursor into a tube furnace, presintering under the protection of flowing inert atmosphere to pyrolyze a carbon source, roasting again, and finally cooling along with the furnace to obtain the sodium vanadium trifluorophosphate anode material of the sodium ion battery.
Compared with the prior art, the invention has the beneficial effects that:
(1) The invention prepares the sodium ion battery anode material sodium vanadium trifluorophosphate by a simple sol-gel method and a high-temperature solid phase sintering reaction, and the charge-discharge curve does not show 3.3V (vs Na) caused by the mixed phase of the sodium vanadium phosphate + and/Na), indirectly improving the average working voltage and energy density of the positive electrode material. The fact proves that the specific energy of the positive electrode material of the sodium vanadium sodium trifluorophosphate ion battery prepared by the invention reaches 446.1mWh/g when the first discharge is carried out at 1C multiplying power, and the specific energy of the discharge still reaches 410.4mWh/g after 300 circles of circulation. The specific energy of the sodium vanadium trifluorophosphate prepared in the comparative example is 358.2mWh/g for the first time, and the specific energy of the sodium vanadium trifluorophosphate after 300 times of circulation is 289.5mWh/g. In contrast, the energy density value of the sodium vanadium trifluorophosphate prepared by the method is obviously improved.
(2) The preparation method has the advantages of easily obtained raw materials, simple operation, low cost and good reproducibility, and the prepared sodium vanadium trifluorophosphate anode material of the sodium ion battery has excellent multiplying power and cycle performance and can meet the actual application requirement of the sodium ion battery. The fact proves that the first discharge specific capacity of the sodium vanadium sodium trifluorophosphate ion battery anode material prepared by the invention under the 1C multiplying power is 119.4mAh/g, and the value is close to the theoretical specific capacity (128.3 mAh/g). And after 300 times of circulation, the capacity retention rate reaches 92.4%, and the good circulation performance is shown. Meanwhile, under the high current density of 10 ℃, the discharge specific capacity of the sodium vanadium sodium trifluorophosphate ion battery anode material prepared by the invention can still reach 110.3mAh/g, and the excellent rate capability is shown.
(3) The invention optimizes the synthesis conditions and technological parameters in the process of preparing sodium ion battery anode material sodium vanadium trifluorophosphate. In particular, a strategy and an operation mode for adjusting the pH value of a precursor solution by adopting a carbon source with a pH buffering effect and changing the proportion of different types of carbon sources are provided, so that the operability of adjusting the pH value of the solution in a large amount of solutions is improved.
Drawings
FIG. 1 is an X-ray diffraction pattern of the sodium vanadium trifluorophosphate material prepared in example 1 and comparative example 1;
FIG. 2 is a graph of the first charge-discharge cycle of sodium vanadium trifluorophosphate as the positive electrode material of the sodium ion battery prepared in example 1 at a 1C rate;
FIG. 3 is a graph of a first charge-discharge cycle of sodium vanadium trifluorophosphate as a cathode material of the sodium ion battery prepared in comparative example 1 at a 1C rate;
FIG. 4 is a graph of a first charge-discharge cycle of sodium vanadium trifluorophosphate as a positive electrode material of the sodium ion battery prepared in comparative example 2 at a 1C rate;
FIG. 5 is a graph showing the differential capacity of the sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared in example 1 in the first cycle at 1C rate;
FIG. 6 is a graph showing the differential capacity of the sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared in comparative example 1 in the first cycle at 1C rate;
FIG. 7 is a graph showing the differential capacity of the sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared in comparative example 2 in the first cycle at 1C rate;
FIG. 8 is a graph showing the specific discharge capacity versus cycle number performance of sodium vanadium trifluorophosphate as a cathode material of sodium ion batteries prepared in example 1, comparative example 1 and comparative example 2 at a 1C rate;
FIG. 9 is a graph showing the energy density versus cycle number performance of sodium vanadium trifluorophosphate as a cathode material for sodium ion batteries prepared in example 1, comparative example 1, and comparative example 2 at a 1C rate;
fig. 10 is a graph showing the rate performance of sodium vanadium trifluorophosphate as a positive electrode material of sodium ion batteries prepared in example 1, comparative example 1 and comparative example 2.
Detailed Description
The following description of the present invention refers to the accompanying drawings and examples, but is not limited to the same, and modifications and equivalents of the present invention can be made without departing from the spirit and scope of the present invention.
The invention has the innovation points of controlling the roasting temperature of the material and adjusting the pH value of the precursor solution, thereby reducing volatilization of fluorine element in the synthesis process. In practice, it is difficult to ensure the consistency of the pH of each part of the solution for a large amount of solution because the pH adjustment often needs to be performed by matching with a pH paper or a pH meter. In view of this, the present invention proposes to adjust the pH of the precursor solution by adding aqueous ammonia dropwise, and also proposes to directly add a carbon source having a pH buffering function to achieve the purpose of adjusting the pH. The added carbon source not only serves as a coating material, a reducing agent and a chelating agent, but also serves as a pH buffering agent, and the pH of the precursor solution can be regulated and controlled within a certain range by dropwise adding ammonia water and changing the adding amount and the proportion of different types of carbon sources.
The first embodiment is as follows: the embodiment describes a preparation method of sodium ion battery positive electrode material sodium vanadium trifluorophosphate, wherein 3.3V (vs. Na) caused by mixed phase does not appear in a constant current charge-discharge curve of the obtained positive electrode material + Na), the method comprising the steps of:
step one: at room temperature, dissolving a carbon source in deionized water, and stirring and mixing uniformly to obtain a clear solution M 1 Regulate M 1 Is weakly acidic; in this step, the total molar amount of carbon source added is subjected to solution M 1 Limiting the maximum dissolution of the raw materials, operating processThe carbon source added and other raw materials (vanadium source, phosphorus source, sodium source and fluorine source) added later are required to be completely dissolved in the solution;
step two: weighing the raw materials and taking the raw materials and the total carbon source as a molar ratio of 5:2, adding it to solution M 1 In the process, a clear solution M is obtained after stirring and heating conditions are maintained for 20 to 30 minutes 2 The method comprises the steps of carrying out a first treatment on the surface of the The purpose of stirring and heating in the step is to enable the vanadium source to have full complexation reaction with the added carbon source;
step three: weighing a phosphorus source, a sodium source and a fluorine source, and adding the phosphorus source, the sodium source and the fluorine source into the solution M 2 In the process, stirring and heating conditions are kept for 10 to 15 minutes to obtain a clear solution M 3 The method comprises the steps of carrying out a first treatment on the surface of the The purpose of stirring and heating in this step is to allow the added raw materials to be thoroughly mixed and dissolved; the feeding sequence in the invention is related to controlling experimental conditions, the carbon source is dissolved firstly to facilitate the subsequent adjustment of pH value, and then the vanadium source is dissolved, so that the subsequent raw materials are dissolved only after the vanadium source is dissolved because the vanadium source is dissolved slowly. After dissolving the vanadium source, adding other raw materials;
step four: the stirring and heating conditions are kept unchanged, so that the solution M 3 The water in the solution M is evaporated continuously after 8 to 12 hours 3 Gradually changing into black sol to finally form gel P containing a small amount of water 1 ；
Step five: transferring the gel in the fourth step into a vacuum drying oven, vacuumizing, heating and drying to obtain xerogel P after the completion of the drying 2 ；
Step six: taking out the xerogel in the step five, grinding with a pestle or ball milling to obtain a powdery precursor, then placing the powdery precursor into a tube furnace, presintering under the protection of flowing inert atmosphere to pyrolyze a carbon source, roasting again, and finally cooling along with the furnace to obtain the sodium vanadium trifluorophosphate anode material of the sodium ion battery. The chemical formula is Na 3 V 2 (PO 4 ) 2 F 3 The mass percentage of the catalyst is more than 95 percent.
The second embodiment is as follows: in the method for preparing the sodium vanadium trifluorophosphate serving as the positive electrode material of the sodium ion battery, in the first step, the carbon source is organic acid and/or ammonium salt, and the organic acid is citric acid monohydrate and/or citric acid anhydrous; the ammonium salt is one or more of ammonium dihydrogen citrate, diammonium hydrogen citrate and triammonium citrate. When the first and second carbon sources are added at the same time, the acid and the acid ammonium salt form a pH conjugated acid-base pair with a buffering function in the solution.
And a third specific embodiment: in the first step, the weak acidity means that the pH is 3.0-5.0. The purpose is to accelerate the complex reaction in the second step, inhibit the hydrolysis of fluorine and reduce the volatilization of fluorine.
The specific embodiment IV is as follows: the method for preparing sodium vanadium trifluorophosphate as the positive electrode material of the sodium ion battery in the third embodiment comprises two ways of adjusting the solution to be slightly acidic: firstly, directly dripping ammonia water into the solution; and secondly, on the premise that the total amount of the carbon sources to be added is selected in the first step, simultaneously selecting and adding the organic acid carbon sources and the ammonium salt carbon sources, and adjusting the proportion and the corresponding dosage of the two carbon sources.
Fifth embodiment: the method for preparing sodium vanadium trifluorophosphate as a cathode material of a sodium ion battery in the fourth embodiment, wherein the molar ratio of citrate in the organic acid carbon source to ammonium ion in the ammonium salt carbon source is 0.4-0.8.
Specific embodiment six: in the preparation method of sodium vanadium trifluorophosphate as the positive electrode material of the sodium ion battery, in the second, third and fourth steps, the heating condition is 45-75 ℃ in the process of removing a large amount of moisture of the precursor solution to obtain sol. The aim is to reduce the volatilization of fluorine elements as much as possible while removing residual free water in the sol.
Seventh embodiment: the preparation method of the sodium ion battery anode material sodium vanadium trifluorophosphate comprises the following steps of preparing a sodium ion battery anode material sodium vanadium trifluorophosphate, wherein a vanadium source is one or a mixture of a plurality of vanadium pentoxide, ammonium metavanadate and vanadyl oxalate; the phosphorus source is one or a mixture of more of monoammonium phosphate, diammonium phosphate and ammonium phosphate; the sodium source is one or a mixture of more of sodium fluoride, sodium acetate, sodium carbonate and sodium nitrate; the fluorine source is ammonium fluoride and/or sodium fluoride.
Eighth embodiment: in the fifth step, the vacuum heating and drying temperature is 60-80 ℃, the time is 6-12 h, the vacuum degree is 0.1MPa, and the purpose is to remove residual free water and reduce volatilization of fluorine element in the following steps of presintering and roasting.
Detailed description nine: in the sixth step, the ball milling speed is 200-300 r/min and the time is 10-15 min, so as to grind xerogel and reduce volatilization of fluorine element.
Detailed description ten: in the method for preparing the sodium vanadium trifluorophosphate serving as the positive electrode material of the sodium ion battery, in the sixth step, the presintering temperature is 250-350 ℃ and the presintering time is 4-8 hours, so that the carbon source is fully pyrolyzed; the roasting temperature is 550-650 ℃ and the time is 6-10 hours, so that the carbothermic reduction reaction is fully carried out and the volatilization of fluorine element is reduced; the heating rate of the tube furnace is set to be 5-10 ℃/min.
Eleventh embodiment: in the method for preparing the sodium vanadium trifluorophosphate as the positive electrode material of the sodium ion battery, in the sixth step, the inert atmosphere is one of argon, nitrogen and hydrogen-argon mixed gas.
Example 1:
(1) Synthesis of 2mmol of the target product Na 3 V 2 (PO 4 ) 2 F 3 Samples were prepared for elemental composition and for the ratios of the elements. Firstly, 100mL of deionized water is measured, 0.6724g of citric acid monohydrate solid is added, and the mixture is stirred and dissolved to obtain a clarified citric acid solution;
(2) Dropwise adding ammonia water with the mass fraction of 20% into the citric acid solution under the monitoring of a pH meter until the pH value of the solution is equal to 4.0;
(3) Adding 0.364g of vanadium pentoxide into the pH-adjusted solution, heating and stirring at 70 ℃ for 30 minutes, and sequentially changing the yellow suspension into light yellow clear liquid and light green clear liquid;
(4) Sequentially weighing 0.46g of monoammonium phosphate and 0.252g of sodium fluoride, adding into the light green clarified liquid, continuously maintaining the temperature of 70 ℃ and heating and stirring for 15 minutes, wherein the light green clarified liquid is observed to be changed into reddish brown clarified liquid;
(5) Heating and stirring at 70 ℃ to remove a large amount of water in the reddish brown clarified liquid, and obtaining viscous light green sol after about 8 hours;
(6) Placing the light green sol into a vacuum drying oven, and drying for 6 hours in vacuum (0.1 MPa) at 70 ℃ to obtain yellow green xerogel;
(7) After the xerogel was ground in a ball mill, it was transferred to a tube furnace. Under the protection of flowing high-purity argon, the temperature is raised to 300 ℃ at the temperature rise rate of 5 ℃ per minute for presintering for 4 hours, then the mixture is heated to 600 ℃ at the temperature rise rate of 5 ℃ per minute for roasting for 8 hours, and the mixture is cooled along with a furnace to obtain the sodium ion battery anode material Na 3 V 2 (PO 4 ) 2 F 3 。
The sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared by the embodiment is assembled to simulate a sodium ion battery, electrochemical performance test is carried out in a 2-4.3V interval, the initial discharge specific capacity can reach 119.4mAh/g, the discharge specific capacity after 300 times of circulation can reach 110.4mAh/g, and the capacity retention rate is 92.4%. The discharge specific capacities of the materials at 1, 5 and 10C are 121.7, 118.3 and 110.3mAh/g respectively.
Example 2:
(1) Synthesis of 4mmol of the target product Na 3 V 2 (PO 4 ) 2 F 3 Samples were prepared for elemental composition and for the ratios of the elements. Firstly, 30mL of deionized water is measured, 0.336g of citric acid monohydrate solid and 1.1675g of citric acid triammonium solid are added, and stirring and dissolving are carried out;
(2) Adding 0.728g of vanadium pentoxide into the solution, heating and stirring for 30 minutes at 70 ℃, and sequentially changing the yellow suspension into light yellow clear liquid and light green clear liquid;
(3) Sequentially weighing 0.92g of monoammonium phosphate and 0.454g of sodium fluoride, adding into the light green clarified liquid, continuously maintaining the temperature of 70 ℃ and heating and stirring for 15 minutes, wherein the light green clarified liquid is observed to be changed into reddish brown clarified liquid;
(4) Heating and stirring at 70 ℃ to remove a large amount of water in the reddish brown clarified liquid, and obtaining viscous light green sol after about 8 hours;
(5) Placing the light green sol into a vacuum drying oven, and drying for 6 hours in vacuum (0.1 MPa) at 70 ℃ to obtain yellow green xerogel;
(6) After the xerogel was ground in a ball mill, it was transferred to a tube furnace. Under the protection of flowing high-purity argon, the temperature is raised to 350 ℃ at a temperature rise rate of 5 ℃ per minute for presintering for 4 hours, then the mixture is heated to 600 ℃ at a temperature rise rate of 5 ℃ per minute for roasting for 10 hours, and the mixture is cooled along with a furnace to obtain the sodium ion battery anode material Na 3 V 2 (PO 4 ) 2 F 3 。
Example 3:
(1) Synthesis of 2mmol of the target product Na 3 V 2 (PO 4 ) 2 F 3 Samples were prepared for elemental composition and for the ratios of the elements. Firstly, 100mL of deionized water is measured, 0.768g of anhydrous citric acid solid is added, and the solution is stirred and dissolved to obtain a clarified citric acid solution;
(2) Dropwise adding 20% ammonia water to the citric acid solution until the pH value of the solution is about 4.5 under the monitoring of a pH meter;
(3) Adding 0.364g of vanadium pentoxide into the pH-adjusted solution, heating and stirring at 75 ℃ for 25 minutes, and sequentially changing the yellow suspension into light yellow clear liquid and light green clear liquid;
(4) Sequentially weighing 0.528g of diammonium phosphate, 0.222g of ammonium fluoride and 0.318g of sodium carbonate, adding into the light green clarified liquid, continuously maintaining the temperature of 75 ℃ and heating and stirring for 10 minutes, wherein the light green clarified liquid is observed to be changed into a reddish brown clarified liquid;
(5) Heating and stirring at 75 ℃ to remove a large amount of water in the reddish brown clarified liquid, and obtaining viscous light green sol after about 6 hours;
(6) Placing the light green sol into a vacuum drying oven, and drying for 8 hours in vacuum (0.1 MPa) at 60 ℃ to obtain yellow green xerogel;
(7) After the xerogel was ground in a ball mill, it was transferred to a tube furnace. Under the protection of flowing high-purity argon, the temperature is raised to 350 ℃ at the temperature rise rate of 8 ℃ per minute for presintering for 4 hours, then the sodium ion battery anode material Na is obtained by roasting for 9 hours at the temperature rise rate of 600 ℃ at the temperature rise rate of 8 ℃ per minute and cooling along with a furnace 3 V 2 (PO 4 ) 2 F 3 。
Comparative example 1:
(1) Synthesis of 2mmol of the target product Na 3 V 2 (PO 4 ) 2 F 3 Samples were prepared for elemental composition and for the ratios of the elements. Firstly, 100mL of deionized water is measured, 0.6724g of citric acid monohydrate solid is added, and the mixture is stirred and dissolved to obtain a clarified citric acid solution;
(2) Adding 0.364g of vanadium pentoxide into the citric acid solution, and heating and stirring at 70 ℃ for 30 minutes to sequentially change the yellow suspension into pale yellow clear liquid and pale green clear liquid;
(3) Sequentially weighing 0.46g of monoammonium phosphate and 0.252g of sodium fluoride, adding into the light green clarified liquid, continuously maintaining the temperature of 75 ℃ and heating and stirring for 10 minutes, wherein the light green clarified liquid is observed to be changed into reddish brown clarified liquid;
(4) Heating and stirring at 70 ℃ to remove a large amount of water in the reddish brown clarified liquid, and obtaining viscous light green sol after about 8 hours;
(5) Placing the light green sol into a vacuum drying oven, and drying for 6 hours in vacuum (0.1 MPa) at 70 ℃ to obtain yellow green xerogel;
(6) After the xerogel was ground in a ball mill, it was transferred to a tube furnace. Under the protection of flowing high-purity argon, the temperature is raised to 300 ℃ at a temperature rise rate of 5 ℃ per minute for presintering for 3.5 hours, then the temperature is raised to 660 ℃ at a temperature rise rate of 5 ℃ per minute for roasting for 8 hours, and the sodium ion battery anode material is obtained after cooling along with a furnaceMaterial Na 3 V 2 (PO 4 ) 2 F 3 。
The sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared in the comparative example is assembled to simulate a sodium ion battery, electrochemical performance test is carried out in a 2-4.3V interval, the initial discharge specific capacity can reach 102.4mAh/g, the discharge specific capacity after 300 times of circulation can reach 82.9mAh/g, and the capacity retention rate is 80.9%. The discharge specific capacities of the materials at 1, 5 and 10C are 103.5, 63.2 and 53.8mAh/g respectively.
Comparative example 2:
(1) Synthesis of 2mmol of the target product Na 3 V 2 (PO 4 ) 2 F 3 Samples were prepared for elemental composition and for the ratios of the elements. Firstly, 100mL of deionized water is measured, 0.6724g of citric acid monohydrate solid is added, and the mixture is stirred and dissolved to obtain a clarified citric acid solution;
(2) Dropwise adding 20% ammonia water to the citric acid solution until the pH value of the solution is about 4.0 under the monitoring of a pH meter;
(3) Adding 0.364g of vanadium pentoxide into the pH-adjusted solution, heating and stirring for 30 minutes at 70 ℃, and sequentially changing the yellow suspension into light yellow clear liquid and light green clear liquid;
(4) Sequentially weighing 0.46g of monoammonium phosphate and 0.252g of sodium fluoride, adding into the light green clarified liquid, continuously maintaining the temperature of 75 ℃ and heating and stirring for 10 minutes, wherein the light green clarified liquid is observed to be changed into reddish brown clarified liquid;
(5) Heating and stirring at 70 ℃ to remove a large amount of water in the reddish brown clarified liquid, and obtaining viscous light green sol after about 8 hours;
(6) Placing the light green sol into a vacuum drying oven, and firstly drying the light green sol for 6 hours under vacuum (0.1 MPa) at 50 ℃ and then drying the light green sol for 6 hours under vacuum at 70 ℃ to obtain yellow green xerogel;
(7) After the xerogel was ground in a ball mill, it was transferred to a tube furnace. Under the protection of flowing high-purity argon, the temperature is raised to 300 ℃ at a temperature rise rate of 5 ℃ per minute for presintering for 3.5 hours, and then is raised to 5 ℃ per minute at a temperature rise rateRoasting at 660 ℃ for 8 hours, and cooling along with a furnace to obtain Na-ion battery anode material 3 V 2 (PO 4 ) 2 F 3 。
Comparative example 2 differs from example 1 in that the firing temperature after burn-in was 660 degrees celsius. The sodium vanadium trifluorophosphate prepared in the comparative example is used as a positive electrode material of a sodium ion battery to assemble a simulated button sodium ion battery, electrochemical performance test is carried out in a 2-4.3V interval, the initial discharge specific capacity can reach 119.0mAh/g, and the discharge specific capacity after 300 times of circulation is 99.0
mAh/g, capacity retention was 83.1%. The discharge specific capacities of the materials at 1, 5 and 10C are 118.0, 109.3 and 99.7mAh/g respectively.
FIG. 1 is an X-ray diffraction pattern of sodium vanadium trifluorophosphate as a positive electrode material of sodium ion batteries prepared in example 1 and comparative example 1 of the present invention. As can be seen from FIG. 1, the product obtained in example 1 maintains the structure of sodium vanadium trifluorophosphate and has high purity and crystallinity. Whereas the X-ray diffraction spectrum of comparative example 1 showed some impurity peaks, the purity was relatively low.
Fig. 2 is a first charge-discharge cycle curve of sodium vanadium trifluorophosphate as a positive electrode material of a sodium ion battery prepared in example 1 of the present invention at a 1C rate. As shown in FIG. 2, when charge-discharge cycles are carried out at 25 ℃ and 1C multiplying power within the voltage range of 2.0-4.3V, the first discharge capacity of the sodium vanadium trifluorophosphate anode material of the sodium ion battery prepared in the example 1 is 119.4mAh/g. The initial discharge capacity of comparative example 2 shown in FIG. 4 was 119.0mAh/g. In contrast, comparative example 1 shown in FIG. 3 has a lower initial discharge capacity of 102.4mAh/g.
Fig. 5 is a differential capacity curve of the sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared in example 1 of the present invention in the first cycle at 1C rate. As can be seen from FIG. 5, the product obtained in example 1 completely eliminates 3.3V (vs.Na + Na) about the discharge plateau. Whereas comparative example 1 shown in FIG. 7 shows a 3.3V (vs.Na + Na) and the X-ray diffraction spectrum thereof, and the phenomenon that the X-ray diffraction spectrum thereof shows a hetero peak. Comparative example 2 shown in FIG. 7 also shows 3.3V (vs.Na + Na) about the discharge plateau. But from the discharge specific capacity corresponding to the plateau, relative to the graph3 comparative example 1, 3.3V (vs.na) + Na) is smaller than the specific capacity corresponding to the discharge plateau. These results demonstrate that in addition to the pH of the precursor solution, the firing temperature of the material is also one of the factors affecting the formation of the impurity phase, and that the firing temperature affects 3.3V (vs.Na + /Na) or not can be completely eliminated.
FIG. 8 is a graph showing the specific capacity-cycle number performance curve of sodium vanadium trifluorophosphate as a positive electrode material of a sodium ion battery prepared in example 1 of the present invention at a 1C rate, wherein the discharge capacity after 300 cycles is 110.4mAh/g, the capacity retention rate is 92.4%, and the excellent cycle performance is shown. And the discharge capacity of the comparative example 1 after 300 circles is only 82.9mAh/g, the capacity retention rate is 80.9%, and the cycle performance is poor; the first discharge specific capacity of comparative example 2 can reach 119.0mAh/g, the discharge specific capacity after 300 times of circulation is 99.0mAh/g, the capacity retention rate is 83.1%, and the circulation performance is relatively poor.
FIG. 9 is a graph showing the specific energy of discharge versus cycle number performance of the sodium ion battery positive electrode material sodium vanadium trifluorophosphate prepared in example 1 of the present invention at a 1C rate, wherein the specific energy of the first discharge is 446.1mWh/g, the specific energy of the discharge after 300 cycles is 410.4mWh/g, and the energy density is high. Comparative example 2 the specific energy for the first discharge was 443.0mWh/g and after 300 cycles the specific energy for the discharge was 359.6mWh/g. Whereas comparative example 1 had a specific energy of 358.2mWh/g for the first discharge, the specific energy of 289.5mWh/g after 300 cycles. From this, the energy density of the sodium vanadium trifluorophosphate prepared in example 1 was significantly improved relative to that of comparative example 1.
Fig. 10 shows the capacity performance of the positive electrode material sodium vanadium trifluorophosphate of the sodium ion battery prepared in example 1 of the present invention under different multiplying powers. As shown in FIG. 10, the positive electrode materials of the sodium ion battery prepared in the example 1 have specific discharge capacities of 121.7, 118.3 and 110.3mAh/g respectively, and exhibit good rate performance when the positive electrode materials are charged and discharged at 1C, 5C and 10C. While the discharge specific capacities of comparative example 1 at 1, 5 and 10C are 103.5, 63.2 and 53.8mAh/g respectively, the rate capability is relatively poor.
Claims (7)
1. A preparation method of sodium ion battery anode material sodium vanadium trifluorophosphate is characterized by comprising the following steps: the method comprises the following steps:
step one: at room temperature, dissolving a carbon source in deionized water, stirring and mixing uniformly to obtain a clear solution M1, and regulating the pH value of the solution M1 to be slightly acidic; the carbon source is organic acid and/or ammonium salt, and the organic acid is citric acid monohydrate and/or citric acid anhydrous; the ammonium salt is one or a mixture of more of ammonium dihydrogen citrate, diammonium hydrogen citrate and triammonium citrate; the weak acidity means that the pH is 3.0-5.0; the means for adjusting the solution to be weakly acidic include two types: firstly, directly dripping ammonia water into the solution; secondly, on the premise that the total amount of the carbon sources to be added is selected in the first step, simultaneously selecting and adding the organic acid carbon sources and the ammonium salt carbon sources; the molar ratio of the citrate in the organic acid carbon source to the ammonium ion in the ammonium salt carbon source is 0.4-0.8;
step two: weighing the raw materials and taking the raw materials and the total carbon source as a molar ratio of 5:2, adding the vanadium source into the solution M1, and maintaining stirring and heating conditions for 20-30 min to obtain a clear solution M2;
step three: weighing a phosphorus source, a sodium source and a fluorine source, adding the phosphorus source, the sodium source and the fluorine source into the solution M2, and maintaining stirring and heating conditions for 10-15 min to obtain a clear solution M3;
step four: the stirring and heating conditions are kept unchanged, so that the water in the solution M3 is evaporated continuously, the solution M3 is gradually changed into black sol after 8-12 hours, and finally gel P1 is formed;
step five: transferring the gel in the step four into a vacuum drying oven, vacuumizing, heating and drying to obtain xerogel P2 after the completion of the vacuum drying;
step six: taking out the xerogel in the step five, grinding with a pestle or ball milling to obtain a powdery precursor, then placing the powdery precursor into a tube furnace, presintering under the protection of flowing inert atmosphere to pyrolyze a carbon source, roasting again, and finally cooling along with the furnace to obtain the sodium vanadium trifluorophosphate anode material of the sodium ion battery.
2. The method for preparing sodium ion battery anode material sodium vanadium trifluorophosphate according to claim 1, which is characterized in that: in the second, third and fourth steps, the heating condition is 45-75 ℃.
3. The method for preparing sodium ion battery anode material sodium vanadium trifluorophosphate according to claim 1, which is characterized in that: the vanadium source is one or a mixture of more of vanadium pentoxide, ammonium metavanadate and vanadyl oxalate; the phosphorus source is one or a mixture of more of monoammonium phosphate, diammonium phosphate and ammonium phosphate; the sodium source is one or a mixture of more of sodium fluoride, sodium acetate, sodium carbonate and sodium nitrate; the fluorine source is ammonium fluoride and/or sodium fluoride.
4. The method for preparing sodium ion battery anode material sodium vanadium trifluorophosphate according to claim 1, which is characterized in that: and fifthly, the temperature of vacuum heating and drying is 60-80 ℃, the time is 6-12 h, and the vacuum degree is 0.1MPa.
5. The method for preparing sodium ion battery anode material sodium vanadium trifluorophosphate according to claim 1, which is characterized in that: in the sixth step, the rotation speed of the ball milling is 200-300 r/min, and the time is 10-15 min.
6. The method for preparing sodium ion battery anode material sodium vanadium trifluorophosphate according to claim 1, which is characterized in that: in the sixth step, the presintering temperature is 250-350 ℃ and the presintering time is 4-8 h; the roasting temperature is 550-650 ℃ and the roasting time is 6-10 h; the heating rate of the tube furnace is set to be 5-10 ℃/min.
7. The method for preparing sodium ion battery anode material sodium vanadium trifluorophosphate according to claim 1, which is characterized in that: in the sixth step, the inert atmosphere is one of argon, nitrogen and hydrogen-argon mixed gas.
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Effective date of registration: 20240410 Address after: No. 70, Group 2, Gushuzi Village, Mengjia Township, Faku County, Shenyang City, Liaoning Province, 110419 Patentee after: Wang Di Country or region after: China Address before: 150001 No. 92 West straight street, Nangang District, Heilongjiang, Harbin Patentee before: HARBIN INSTITUTE OF TECHNOLOGY Country or region before: China |