CN112390240A - Preparation method of three-dimensional ordered spherical lithium iron phosphate material - Google Patents
Preparation method of three-dimensional ordered spherical lithium iron phosphate material Download PDFInfo
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- GELKBWJHTRAYNV-UHFFFAOYSA-K lithium iron phosphate Chemical compound [Li+].[Fe+2].[O-]P([O-])([O-])=O GELKBWJHTRAYNV-UHFFFAOYSA-K 0.000 title claims abstract description 93
- 239000000463 material Substances 0.000 title claims abstract description 46
- 238000002360 preparation method Methods 0.000 title claims abstract description 20
- 239000013078 crystal Substances 0.000 claims abstract description 36
- 239000004793 Polystyrene Substances 0.000 claims abstract description 35
- 229920002223 polystyrene Polymers 0.000 claims abstract description 35
- 239000002243 precursor Substances 0.000 claims abstract description 30
- 238000001035 drying Methods 0.000 claims abstract description 18
- 238000005245 sintering Methods 0.000 claims abstract description 14
- 238000001816 cooling Methods 0.000 claims abstract description 8
- 238000006116 polymerization reaction Methods 0.000 claims abstract description 8
- 238000010438 heat treatment Methods 0.000 claims description 34
- 238000003756 stirring Methods 0.000 claims description 28
- MNCGMVDMOKPCSQ-UHFFFAOYSA-M sodium;2-phenylethenesulfonate Chemical compound [Na+].[O-]S(=O)(=O)C=CC1=CC=CC=C1 MNCGMVDMOKPCSQ-UHFFFAOYSA-M 0.000 claims description 19
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Chemical compound O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 claims description 19
- XEEYBQQBJWHFJM-UHFFFAOYSA-N iron Substances [Fe] XEEYBQQBJWHFJM-UHFFFAOYSA-N 0.000 claims description 18
- -1 iron alkoxide Chemical class 0.000 claims description 15
- SNKMVYBWZDHJHE-UHFFFAOYSA-M lithium;dihydrogen phosphate Chemical compound [Li+].OP(O)([O-])=O SNKMVYBWZDHJHE-UHFFFAOYSA-M 0.000 claims description 14
- 229910000028 potassium bicarbonate Inorganic materials 0.000 claims description 14
- 235000015497 potassium bicarbonate Nutrition 0.000 claims description 14
- 239000011736 potassium bicarbonate Substances 0.000 claims description 14
- TYJJADVDDVDEDZ-UHFFFAOYSA-M potassium hydrogencarbonate Chemical compound [K+].OC([O-])=O TYJJADVDDVDEDZ-UHFFFAOYSA-M 0.000 claims description 14
- IJGRMHOSHXDMSA-UHFFFAOYSA-N Atomic nitrogen Chemical compound N#N IJGRMHOSHXDMSA-UHFFFAOYSA-N 0.000 claims description 12
- 229910052742 iron Inorganic materials 0.000 claims description 11
- 238000000034 method Methods 0.000 claims description 11
- 239000008367 deionised water Substances 0.000 claims description 8
- 229910021641 deionized water Inorganic materials 0.000 claims description 8
- LFQSCWFLJHTTHZ-UHFFFAOYSA-N Ethanol Chemical compound CCO LFQSCWFLJHTTHZ-UHFFFAOYSA-N 0.000 claims description 7
- 239000003999 initiator Substances 0.000 claims description 7
- PPBRXRYQALVLMV-UHFFFAOYSA-N Styrene Chemical group C=CC1=CC=CC=C1 PPBRXRYQALVLMV-UHFFFAOYSA-N 0.000 claims description 6
- 238000007720 emulsion polymerization reaction Methods 0.000 claims description 6
- 229910052757 nitrogen Inorganic materials 0.000 claims description 6
- 239000012074 organic phase Substances 0.000 claims description 6
- USHAGKDGDHPEEY-UHFFFAOYSA-L potassium persulfate Chemical compound [K+].[K+].[O-]S(=O)(=O)OOS([O-])(=O)=O USHAGKDGDHPEEY-UHFFFAOYSA-L 0.000 claims description 6
- 238000010992 reflux Methods 0.000 claims description 6
- 238000009210 therapy by ultrasound Methods 0.000 claims description 6
- ZSSJELASBNTVGR-UHFFFAOYSA-N [N+](=O)(O)[O-].[N+](=O)(O)[O-].[N+](=O)(O)[O-].NC(=O)N.NC(=O)N.NC(=O)N.NC(=O)N.NC(=O)N.NC(=O)N Chemical group [N+](=O)(O)[O-].[N+](=O)(O)[O-].[N+](=O)(O)[O-].NC(=O)N.NC(=O)N.NC(=O)N.NC(=O)N.NC(=O)N.NC(=O)N ZSSJELASBNTVGR-UHFFFAOYSA-N 0.000 claims description 4
- 239000002245 particle Substances 0.000 abstract description 9
- 238000010556 emulsion polymerization method Methods 0.000 abstract description 5
- 229920001577 copolymer Polymers 0.000 abstract description 3
- 230000035484 reaction time Effects 0.000 abstract description 3
- 239000004005 microsphere Substances 0.000 abstract description 2
- 239000000084 colloidal system Substances 0.000 abstract 1
- 239000000203 mixture Substances 0.000 description 17
- 239000000523 sample Substances 0.000 description 15
- 238000002604 ultrasonography Methods 0.000 description 10
- 239000011148 porous material Substances 0.000 description 8
- 239000003981 vehicle Substances 0.000 description 7
- 229910052751 metal Inorganic materials 0.000 description 6
- 239000002184 metal Substances 0.000 description 6
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 5
- 229910001290 LiPF6 Inorganic materials 0.000 description 5
- WHXSMMKQMYFTQS-UHFFFAOYSA-N Lithium Chemical compound [Li] WHXSMMKQMYFTQS-UHFFFAOYSA-N 0.000 description 5
- 229910019142 PO4 Inorganic materials 0.000 description 5
- 239000002033 PVDF binder Substances 0.000 description 5
- 239000004743 Polypropylene Substances 0.000 description 5
- 239000006230 acetylene black Substances 0.000 description 5
- 238000007605 air drying Methods 0.000 description 5
- 239000011248 coating agent Substances 0.000 description 5
- 238000000576 coating method Methods 0.000 description 5
- 239000007788 liquid Substances 0.000 description 5
- 229910052744 lithium Inorganic materials 0.000 description 5
- 239000012528 membrane Substances 0.000 description 5
- 238000002156 mixing Methods 0.000 description 5
- 229920001155 polypropylene Polymers 0.000 description 5
- 239000010405 anode material Substances 0.000 description 4
- 230000000052 comparative effect Effects 0.000 description 4
- 239000003792 electrolyte Substances 0.000 description 4
- 230000003247 decreasing effect Effects 0.000 description 3
- 239000003995 emulsifying agent Substances 0.000 description 3
- HBBGRARXTFLTSG-UHFFFAOYSA-N Lithium ion Chemical compound [Li+] HBBGRARXTFLTSG-UHFFFAOYSA-N 0.000 description 2
- 229910000398 iron phosphate Inorganic materials 0.000 description 2
- WBJZTOZJJYAKHQ-UHFFFAOYSA-K iron(3+) phosphate Chemical compound [Fe+3].[O-]P([O-])([O-])=O WBJZTOZJJYAKHQ-UHFFFAOYSA-K 0.000 description 2
- 239000004816 latex Substances 0.000 description 2
- 229920000126 latex Polymers 0.000 description 2
- 229910001416 lithium ion Inorganic materials 0.000 description 2
- 238000011068 loading method Methods 0.000 description 2
- 238000001000 micrograph Methods 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 125000000542 sulfonic acid group Chemical group 0.000 description 2
- 229910052493 LiFePO4 Inorganic materials 0.000 description 1
- 230000004075 alteration Effects 0.000 description 1
- 238000013459 approach Methods 0.000 description 1
- 230000015572 biosynthetic process Effects 0.000 description 1
- 238000006555 catalytic reaction Methods 0.000 description 1
- 239000010406 cathode material Substances 0.000 description 1
- 238000006243 chemical reaction Methods 0.000 description 1
- 238000000975 co-precipitation Methods 0.000 description 1
- 229910017052 cobalt Inorganic materials 0.000 description 1
- 239000010941 cobalt Substances 0.000 description 1
- GUTLYIVDDKVIGB-UHFFFAOYSA-N cobalt atom Chemical compound [Co] GUTLYIVDDKVIGB-UHFFFAOYSA-N 0.000 description 1
- 238000011161 development Methods 0.000 description 1
- 238000007599 discharging Methods 0.000 description 1
- 230000005611 electricity Effects 0.000 description 1
- 238000003912 environmental pollution Methods 0.000 description 1
- 238000002474 experimental method Methods 0.000 description 1
- 238000005187 foaming Methods 0.000 description 1
- 238000001027 hydrothermal synthesis Methods 0.000 description 1
- 239000012535 impurity Substances 0.000 description 1
- 150000002739 metals Chemical class 0.000 description 1
- 239000000693 micelle Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 231100000956 nontoxicity Toxicity 0.000 description 1
- 239000010450 olivine Substances 0.000 description 1
- 229910052609 olivine Inorganic materials 0.000 description 1
- 239000012071 phase Substances 0.000 description 1
- 230000002035 prolonged effect Effects 0.000 description 1
- 239000012429 reaction media Substances 0.000 description 1
- 230000036632 reaction speed Effects 0.000 description 1
- 238000000926 separation method Methods 0.000 description 1
- 238000003980 solgel method Methods 0.000 description 1
- 238000010532 solid phase synthesis reaction Methods 0.000 description 1
- 238000001179 sorption measurement Methods 0.000 description 1
- 230000000087 stabilizing effect Effects 0.000 description 1
- 239000000126 substance Substances 0.000 description 1
- 238000003786 synthesis reaction Methods 0.000 description 1
- 125000000391 vinyl group Chemical group [H]C([*])=C([H])[H] 0.000 description 1
- 229920002554 vinyl polymer Polymers 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
- C01B25/45—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
- H01M10/052—Li-accumulators
- H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
- H01M4/00—Electrodes
- H01M4/02—Electrodes composed of, or comprising, active material
- H01M4/36—Selection of substances as active materials, active masses, active liquids
- H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
- H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
-
- C—CHEMISTRY; METALLURGY
- C01—INORGANIC CHEMISTRY
- C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
- C01P2004/00—Particle morphology
- C01P2004/30—Particle morphology extending in three dimensions
- C01P2004/32—Spheres
-
- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
- Y02E60/10—Energy storage using batteries
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- Chemical & Material Sciences (AREA)
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- General Chemical & Material Sciences (AREA)
- Inorganic Chemistry (AREA)
- Organic Chemistry (AREA)
- Materials Engineering (AREA)
- Manufacturing & Machinery (AREA)
- Crystallography & Structural Chemistry (AREA)
- Battery Electrode And Active Subsutance (AREA)
Abstract
The invention discloses a preparation method of a three-dimensional ordered spherical lithium iron phosphate material, which comprises the steps of preparing a polystyrene colloidal crystal by a soap-free emulsion polymerization method, then preparing a lithium iron phosphate precursor sol, finally dropwise adding the lithium iron phosphate precursor sol onto the polystyrene colloidal crystal, drying the whole polystyrene colloidal crystal overnight by air flow after the lithium iron phosphate precursor sol wets the whole polystyrene colloidal crystal, and then sintering and naturally cooling to obtain the three-dimensional ordered spherical lithium iron phosphate material. The invention adjusts the sphere diameter of the polystyrene colloid crystal by controlling the polymerization reaction time, the system ionic strength and the concentration of the ionic copolymer of the soap-free emulsion polymerization method. The prepared three-dimensional ordered spherical lithium iron phosphate material can maximally retain the integrity and uniformity of a spherical structure, and meanwhile, the particle size of the lithium iron phosphate can be adjusted according to the sphere diameter of the polystyrene microsphere, and the prepared lithium iron phosphate material not only has the characteristics of large specific surface area, high porosity and the like of a common spherical material.
Description
Technical Field
The invention relates to the field of new energy materials and chemical batteries, in particular to a preparation method of a three-dimensional ordered spherical lithium iron phosphate material.
Background
Goodenough et al discovered in 1997 that LiFePO4 with an olivine structure can reversibly intercalate and deintercalate lithium ions at a potential value of 3.4V (vs. Li +/Li), and the material becomes a widely-used cathode material of the current lithium ion battery due to the advantages of low synthesis cost, no toxicity, good safety and stability, and the like. The battery-grade lithium iron phosphate is usually prepared and researched by methods such as a high-temperature solid phase method, a hydrothermal method, a sol-gel method, a coprecipitation method and the like, and an iron phosphate phase formed in the charging process of the lithium iron phosphate is converted again in the discharging process. Since 2019, along with the continuous subsidence of new energy automobiles, the cost advantage of the lithium iron phosphate battery gradually appears, and because the lithium iron phosphate anode material does not contain rare metals such as cobalt and the like, the lithium iron phosphate anode material is absolutely dominant in the markets of passenger cars and special cars by virtue of the cost advantage, the price of the lithium iron phosphate anode material of 2019Q4 is only 4.3 ten thousand yuan/ton, and the price of the ternary 523 anode material is 13.8 ten thousand yuan/ton. Along with the continuous low price of the lithium iron phosphate, the non-power requirements of 5G base station power supplies, low-speed vehicles and the like are activated, the requirements of the lithium iron phosphate material are pulled, the loading amounts of a lithium iron phosphate battery passenger car and a special vehicle in 2019 are respectively 13.9 GWH and 4.3GWH, which account for 91.3% of the whole loading proportion, and the vehicle type proportion of the passenger vehicle carrying the lithium iron phosphate is 18% compared with the proportion of 7.8% of the passenger vehicle in 2019 in the whole year according to the condition display of the first recommended catalog passenger vehicle in 2020 of the Ministry of industry and communications. In recent years, lithium iron phosphate is severely extruded by ternary elements in the field of power, and along with gradual slope receding of subsidies, the marginal influence of the subsidies on new energy vehicles and power batteries is weakened, and safety, cost, cycle frequency, stability and the like become more important. Lithium iron phosphate possesses the cost advantage at present, has living space in the sensitive market of cost, and the performance short slab is promoted to the new technical scheme of stack, and lithium iron phosphate is the big trend in passenger car market rise, and lithium iron phosphate industrial chain demand is expected to be warmed up in the future, and supply and demand pattern will be improved.
The 3DOM material has the advantages of wide pore channel, higher pore volume and the like, and has wide application prospect in the aspects of novel catalysis, adsorption and separation materials. The early porous materials were mostly prepared by foaming and substitution methods, but the porous materials prepared by these methods have inconsistent pore size and pore type, thus limiting their application. The development of colloidal crystals provides a new approach for the preparation of 3DOM materials. The colloidal crystal template method is simple and has a controllable structure, so that the colloidal crystal template method becomes a main method for preparing the 3DOM material at present.
Disclosure of Invention
The invention aims to provide a preparation method of a three-dimensional ordered spherical lithium iron phosphate material, which can improve the electrochemical performance of a lithium iron phosphate battery.
The technical scheme of the invention is as follows:
a preparation method of a three-dimensional ordered spherical lithium iron phosphate material specifically comprises the following steps:
(1) soap-free emulsion polymerization: adding a certain amount of potassium bicarbonate and sodium styrene sulfonate into deionized water, fully stirring to completely dissolve the potassium bicarbonate and the sodium styrene sulfonate, then adding a certain amount of styrene monomer, stirring and refluxing under the protection of nitrogen, heating the solution to 72 ℃, slowly dropwise adding an initiator potassium persulfate solution, and carrying out polymerization reaction in a closed system after dropwise adding to obtain a polystyrene colloidal crystal;
(2) preparing lithium iron phosphate precursor sol: sequentially adding a certain amount of iron alkoxide and lithium dihydrogen phosphate into absolute ethyl alcohol under ultrasonic treatment and stirring at room temperature, continuously performing ultrasonic treatment and stirring, slowly adding deionized water into the solution, and drying to obtain a lithium iron phosphate precursor sol;
(3) dropwise adding the lithium iron phosphate precursor sol onto the polystyrene colloidal crystal, placing the whole polystyrene colloidal crystal after the lithium iron phosphate precursor sol wets the polystyrene colloidal crystal in an air current for drying overnight, then removing the organic-phase polystyrene colloidal crystal through sintering, and finally naturally cooling to obtain the three-dimensional ordered spherical lithium iron phosphate material.
The mass ratio of the potassium bicarbonate to the sodium styrene sulfonate is (2-5) to (0.3-0.5).
In the step (1), the time for carrying out polymerization reaction in a closed system is 24-26 h.
The iron alkoxide is hexaurea trinitrate and iron.
The mass ratio of the hexaurea trinitrate to the lithium dihydrogen phosphate is 1 (1.8-2).
In the step (2), the time for ultrasonic treatment and stirring is 15 min.
In the step (2), the drying temperature is 80 ℃, and the drying time is 12 h.
In the step (3), the sintering is carried out by firstly heating to 300 ℃ at the heating rate of 2 ℃/min in the reducing atmosphere, preserving heat for 3h, then heating to 550 ℃ at the heating rate of 4 ℃/min, and preserving heat for 5 h.
The invention has the advantages that:
the soap-free emulsion polymerization method is a new polymerization method developed on the basis of the traditional emulsion polymerization method. Firstly, no emulsifier or only a small amount of emulsifier (the concentration is lower than the critical micelle concentration CMC) is added in the reaction, so that the experimental cost is reduced, and the problems of impurity of the product, rough surface and the like caused by the emulsifier are solved; and secondly, the reaction medium is water, so that the environmental pollution caused by experiments is effectively reduced. The three-dimensional ordered spherical lithium iron phosphate material prepared by taking the polystyrene colloidal crystal prepared by the soap-free emulsion polymerization method as the template has the characteristics of large specific surface area, high porosity and the like of a common spherical material, and has the characteristics of strong hole structure periodicity, uniform and adjustable pore diameter, communicated pore channels and the like, and the prepared lithium iron phosphate material has good electrochemical performance.
The invention controls the polymerization reaction time and the system ionic strength (KHCO)3Concentration of the lithium iron phosphate material) and the concentration of the ion copolymer (the concentration of the sodium styrene sulfonate) to adjust the sphere diameter of the polystyrene colloidal crystal, and finally realize the adjustment of the particle diameter of the lithium iron phosphate material.
Drawings
Fig. 1 is a scanning electron microscope image of a lithium iron phosphate material prepared in example 1 of the present invention.
Fig. 2 is a scanning electron microscope image of the lithium iron phosphate material prepared in example 2 of the present invention.
Fig. 3 is a graph of the high temperature cycle performance of the batteries according to examples 1, 2, 3, 4 of the present invention and comparative example.
Fig. 4 is a graph of rate discharge performance of batteries prepared according to examples 1, 2, 3, 4 of the present invention and comparative example.
Fig. 5 is a comparison of median particle size D50 of lithium iron phosphate materials prepared in examples 1, 2, 3, and 4 of the present invention.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Example 1
A preparation method of a three-dimensional ordered spherical lithium iron phosphate material specifically comprises the following steps:
(1) soap-free emulsion polymerization: adding 0.2g of potassium bicarbonate and 0.03g of sodium styrene sulfonate into 250mL of deionized water, fully stirring to completely dissolve the potassium bicarbonate and the sodium styrene sulfonate, transferring the mixture into a 500mL four-neck flask, then adding 30mL of styrene monomer into the four-neck flask, stirring and refluxing under the protection of nitrogen, heating the solution to 72 ℃, and slowly dropwise adding 50mL of potassium persulfate (K) containing a certain amount of initiator2S2O8) The solution is dripped in 30min, and a closed system reacts for 24h after dripping;
(2) preparing lithium iron phosphate precursor sol: at room temperature, 5.54g of iron alkoxide (hexaurea ferric trinitrate, [ Fe (H) ]2NCONH2)6](NO3)3) And 10.71 lithium dihydrogen phosphate (LiH)2PO4) Sequentially adding the mixture into 30ml of absolute ethyl alcohol under the conditions of ultrasound and stirring, continuously performing ultrasound and stirring for 15min, slowly adding 30ml of water into the mixture by using a guide pipe (the guide pipe needs to extend below the liquid level when water is added), and drying the mixture for 12h in a forced air drying oven at the temperature of 80 ℃ to obtain lithium iron phosphate precursor sol;
(3) dropwise adding lithium iron phosphate precursor sol onto a polystyrene colloidal crystal, placing the whole polystyrene colloidal crystal after the lithium iron phosphate precursor sol wets the whole polystyrene colloidal crystal in air flow for drying overnight, then removing the organic-phase polystyrene colloidal crystal through sintering, heating the sample to 300 ℃ at the heating rate of 2 ℃/min in the reducing atmosphere during sintering, preserving heat for 3h, heating to 550 ℃ at the heating rate of 4 ℃/min, preserving heat for 5h, and finally naturally cooling with a furnace to obtain the lithium iron phosphate sample.
Mixing the prepared lithium iron phosphate sample, acetylene black and PVDF (polyvinylidene fluoride) according to the mass ratio of 8:1:1, coating to prepare a positive plate, assembling a 2023 type button cell in a glove box, wherein the negative plate is a metal lithium plate, a diaphragm is a Celgard2400 polypropylene porous membrane, and an electrolyte is LiPF6M (EC) and m (DMC) in a concentration of 1.0mol/L, wherein the ratio of m (EMC) to 1:1:1 is used.
As can be seen from fig. 1, the prepared lithium iron phosphate material is spherical.
Example 2
A preparation method of a three-dimensional ordered spherical lithium iron phosphate material specifically comprises the following steps:
(1) soap-free emulsion polymerization: adding 0.2g of potassium bicarbonate and 0.03g of sodium styrene sulfonate into 250mL of deionized water, fully stirring to completely dissolve the potassium bicarbonate and the sodium styrene sulfonate, transferring the mixture into a 500mL four-neck flask, then adding 30mL of styrene monomer into the four-neck flask, stirring and refluxing under the protection of nitrogen, heating the solution to 72 ℃, and slowly dropwise adding 50mL of potassium persulfate (K) containing a certain amount of initiator2S2O8) The solution is dripped in 30min, and the system is closed to react for 26h after dripping;
(2) preparing lithium iron phosphate precursor sol: at room temperature, 5.54g of iron alkoxide (hexaurea ferric trinitrate, [ Fe (H) ]2NCONH2)6](NO3)3) And 10.71 lithium dihydrogen phosphate (LiH)2PO4) Sequentially adding the mixture into 30ml of absolute ethyl alcohol under the conditions of ultrasound and stirring, continuously performing ultrasound and stirring for 15min, slowly adding 30ml of water into the mixture by using a guide pipe (the guide pipe needs to extend below the liquid level when water is added), and drying the mixture for 12h in a forced air drying oven at the temperature of 80 ℃ to obtain lithium iron phosphate precursor sol;
(3) dropwise adding lithium iron phosphate precursor sol onto a polystyrene colloidal crystal, placing the whole polystyrene colloidal crystal after the lithium iron phosphate precursor sol wets the whole polystyrene colloidal crystal in air flow for drying overnight, then removing the organic-phase polystyrene colloidal crystal through sintering, heating the sample to 300 ℃ at the heating rate of 2 ℃/min in the reducing atmosphere during sintering, preserving heat for 3h, heating to 550 ℃ at the heating rate of 4 ℃/min, preserving heat for 5h, and finally naturally cooling with a furnace to obtain the lithium iron phosphate sample.
Mixing the prepared lithium iron phosphate sample, acetylene black and PVDF (polyvinylidene fluoride) according to the mass ratio of 8:1:1, coating to prepare a positive plate, assembling a 2023 type button cell in a glove box, wherein the negative plate is a metal lithium plate, a diaphragm is a Celgard2400 polypropylene porous membrane, and an electrolyte is LiPF6M (EC) and m (DMC) in a concentration of 1.0mol/L, wherein the ratio of m (EMC) to 1:1:1 is used.
As can be seen from fig. 2, the prepared lithium iron phosphate material is spherical.
Example 3
A preparation method of a three-dimensional ordered spherical lithium iron phosphate material specifically comprises the following steps:
(1) soap-free emulsion polymerization: adding 0.5g of potassium bicarbonate and 0.03g of sodium styrene sulfonate into 250mL of deionized water, fully stirring to completely dissolve the potassium bicarbonate and the sodium styrene sulfonate, transferring the mixture into a 500mL four-neck flask, then adding 30mL of styrene monomer into the four-neck flask, stirring and refluxing under the protection of nitrogen, heating the solution to 72 ℃, and slowly dropwise adding 50mL of potassium persulfate (K) containing a certain amount of initiator2S2O8) The solution is dripped in 30min, and a closed system reacts for 24h after dripping;
(2) preparing lithium iron phosphate precursor sol: at room temperature, 5.54g of iron alkoxide (hexaurea ferric trinitrate, [ Fe (H) ]2NCONH2)6](NO3)3) And 10.71 lithium dihydrogen phosphate (LiH)2PO4) Adding into 30ml anhydrous ethanol under ultrasound and stirring, continuously ultrasound and stirring for 15min, slowly adding 30ml water into the mixture with guide tube (the guide tube should extend below liquid level when adding water), and drying in forced air drying oven at 80 deg.C for 12 hr to obtain final productLithium iron phosphate precursor sol;
(3) dropwise adding lithium iron phosphate precursor sol onto a polystyrene colloidal crystal, placing the whole polystyrene colloidal crystal after the lithium iron phosphate precursor sol wets the whole polystyrene colloidal crystal in air flow for drying overnight, then removing the organic-phase polystyrene colloidal crystal through sintering, heating the sample to 300 ℃ at the heating rate of 2 ℃/min in the reducing atmosphere during sintering, preserving heat for 3h, heating to 550 ℃ at the heating rate of 4 ℃/min, preserving heat for 5h, and finally naturally cooling with a furnace to obtain the lithium iron phosphate sample.
Mixing the prepared lithium iron phosphate sample, acetylene black and PVDF (polyvinylidene fluoride) according to the mass ratio of 8:1:1, coating to prepare a positive plate, assembling a 2023 type button cell in a glove box, wherein the negative plate is a metal lithium plate, a diaphragm is a Celgard2400 polypropylene porous membrane, and an electrolyte is LiPF6M (EC) and m (DMC) in a concentration of 1.0mol/L, wherein the ratio of m (EMC) to 1:1:1 is used.
Example 4
A preparation method of a three-dimensional ordered spherical lithium iron phosphate material specifically comprises the following steps:
(1) soap-free emulsion polymerization: adding 0.2g of potassium bicarbonate and 0.05g of sodium styrene sulfonate into 250mL of deionized water, fully stirring to completely dissolve the potassium bicarbonate and the sodium styrene sulfonate, transferring the mixture into a 500mL four-neck flask, then adding 30mL of styrene monomer into the four-neck flask, stirring and refluxing under the protection of nitrogen, heating the solution to 72 ℃, and slowly dropwise adding 50mL of potassium persulfate (K) containing a certain amount of initiator2S2O8) The solution is dripped in 30min, and a closed system reacts for 24h after dripping;
(2) preparing lithium iron phosphate precursor sol: at room temperature, 5.54g of iron alkoxide (hexaurea ferric trinitrate, [ Fe (H) ]2NCONH2)6](NO3)3) And 10.71 lithium dihydrogen phosphate (LiH)2PO4) Sequentially adding the mixture into 30ml of absolute ethyl alcohol under the conditions of ultrasound and stirring, continuously performing ultrasound and stirring for 15min, slowly adding 30ml of water into the mixture by using a guide pipe (the guide pipe needs to extend below the liquid level when water is added), and drying the mixture for 12h in a forced air drying oven at the temperature of 80 ℃ to obtain lithium iron phosphate precursor sol;
(3) dropwise adding lithium iron phosphate precursor sol onto a polystyrene colloidal crystal, placing the whole polystyrene colloidal crystal after the lithium iron phosphate precursor sol wets the whole polystyrene colloidal crystal in air flow for drying overnight, then removing the organic-phase polystyrene colloidal crystal through sintering, heating the sample to 300 ℃ at the heating rate of 2 ℃/min in the reducing atmosphere during sintering, preserving heat for 3h, heating to 550 ℃ at the heating rate of 4 ℃/min, preserving heat for 5h, and finally naturally cooling with a furnace to obtain the lithium iron phosphate sample.
Mixing the prepared lithium iron phosphate sample, acetylene black and PVDF (polyvinylidene fluoride) according to the mass ratio of 8:1:1, coating to prepare a positive plate, assembling a 2023 type button cell in a glove box, wherein the negative plate is a metal lithium plate, a diaphragm is a Celgard2400 polypropylene porous membrane, and an electrolyte is LiPF6M (EC) and m (DMC) in a concentration of 1.0mol/L, wherein the ratio of m (EMC) to 1:1:1 is used.
Comparative example
A preparation method of a lithium iron phosphate material specifically comprises the following steps:
(1) preparing lithium iron phosphate precursor sol: at room temperature, 5.54g of iron alkoxide (hexaurea ferric trinitrate, [ Fe (H) ]2NCONH2)6](NO3)3) And 10.71 lithium dihydrogen phosphate (LiH)2PO4) Sequentially adding the mixture into 30ml of absolute ethyl alcohol under the conditions of ultrasound and stirring, continuously performing ultrasound and stirring for 15min, slowly adding 30ml of water into the mixture by using a guide pipe (the guide pipe needs to extend below the liquid level when water is added), and drying the mixture for 12h in a forced air drying oven at the temperature of 80 ℃ to obtain lithium iron phosphate precursor sol;
(3) sintering the lithium iron phosphate precursor sol, heating to 300 ℃ at a heating rate of 2 ℃/min in a reducing atmosphere, preserving heat for 3h, then heating to 550 ℃ at a heating rate of 4 ℃/min, preserving heat for 5h, and finally naturally cooling along with the furnace to obtain a lithium iron phosphate sample.
Mixing the prepared lithium iron phosphate sample, acetylene black and PVDF (polyvinylidene fluoride) according to the mass ratio of 8:1:1, coating to prepare a positive plate, assembling a 2023 type button cell in a glove box, wherein the negative plate is a metal lithium plate, a diaphragm is a Celgard2400 polypropylene porous membrane, and electricity is suppliedThe hydrolyzed solution is LiPF6M (EC) and m (DMC) in a concentration of 1.0mol/L, wherein the ratio of m (EMC) to 1:1:1 is used.
As can be seen from FIG. 3, when examples 1 to 4 were compared with the comparative sample, the cell capacity fade was slowed and the high-temperature cycle performance was significantly improved. It can be seen from fig. 4 that the rate discharge performance of the battery is improved. As can be seen from fig. 5, after the concentration of the ion copolymer of example 4 is increased (i.e. compared with the concentration of sodium styrene sulfonate in example 1), the particle size of the finally prepared lithium iron phosphate material is decreased (wherein, due to the special structure of sodium styrene sulfonate, one end of the sodium styrene sulfonate contains vinyl, so that it is easily initiated by the initiator to generate oligomer radicals, and the sulfonic acid group at the other end is hydrophilic and can also play a role in stabilizing latex particles, when the concentration of sodium styrene sulfonate is increased, the concentrations of the oligomer radicals and the sulfonic acid group in the system are increased, so that more reactive centers are formed, so that the latex particles in the system are increased and decreased, the reaction speed of the system is increased, the sphere diameter of the polystyrene microsphere is smaller, and the particle size of the finally sintered lithium iron phosphate material is also decreased). As can be seen from fig. 5, after the polymerization reaction time is prolonged in example 2 (i.e., compared with example 1), the particle size of the finally prepared lithium iron phosphate material is increased. As can be seen in FIG. 5, example 3 increases the ionic strength of the system (i.e., compared to KHCO in example 1)3The concentration of the lithium iron phosphate is increased), the particle size of the finally prepared lithium iron phosphate material is increased.
Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that changes, modifications, substitutions and alterations can be made in these embodiments without departing from the principles and spirit of the invention, the scope of which is defined in the appended claims and their equivalents.
Claims (8)
1. A preparation method of a three-dimensional ordered spherical lithium iron phosphate material is characterized by comprising the following steps: the method specifically comprises the following steps:
(1) soap-free emulsion polymerization: adding a certain amount of potassium bicarbonate and sodium styrene sulfonate into deionized water, fully stirring to completely dissolve the potassium bicarbonate and the sodium styrene sulfonate, then adding a certain amount of styrene monomer, stirring and refluxing under the protection of nitrogen, heating the solution to 72 ℃, slowly dropwise adding an initiator potassium persulfate solution, and carrying out polymerization reaction in a closed system after dropwise adding to obtain a polystyrene colloidal crystal;
(2) preparing lithium iron phosphate precursor sol: sequentially adding a certain amount of iron alkoxide and lithium dihydrogen phosphate into absolute ethyl alcohol under ultrasonic treatment and stirring at room temperature, continuously performing ultrasonic treatment and stirring, slowly adding deionized water into the solution, and drying to obtain a lithium iron phosphate precursor sol;
(3) dropwise adding the lithium iron phosphate precursor sol onto the polystyrene colloidal crystal, placing the whole polystyrene colloidal crystal after the lithium iron phosphate precursor sol wets the polystyrene colloidal crystal in an air current for drying overnight, then removing the organic-phase polystyrene colloidal crystal through sintering, and finally naturally cooling to obtain the three-dimensional ordered spherical lithium iron phosphate material.
2. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 1, characterized by comprising the following steps: the mass ratio of the potassium bicarbonate to the sodium styrene sulfonate is (2-5) to (0.3-0.5).
3. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 1, characterized by comprising the following steps: in the step (1), the time for carrying out polymerization reaction in a closed system is 24-26 h.
4. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 1, characterized by comprising the following steps: the iron alkoxide is hexaurea trinitrate and iron.
5. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 4, characterized by comprising the following steps: the mass ratio of the hexaurea trinitrate to the lithium dihydrogen phosphate is 1 (1.8-2).
6. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 1, characterized by comprising the following steps: in the step (2), the time for ultrasonic treatment and stirring is 15 min.
7. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 1, characterized by comprising the following steps: in the step (2), the drying temperature is 80 ℃, and the drying time is 12 h.
8. The preparation method of the three-dimensional ordered spherical lithium iron phosphate material according to claim 1, characterized by comprising the following steps: in the step (3), the sintering is carried out by firstly heating to 300 ℃ at the heating rate of 2 ℃/min in the reducing atmosphere, preserving heat for 3h, then heating to 550 ℃ at the heating rate of 4 ℃/min, and preserving heat for 5 h.
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