CN115403023A - Method for preparing lithium iron manganese phosphate by supercritical hydrothermal method assisted spray drying - Google Patents

Method for preparing lithium iron manganese phosphate by supercritical hydrothermal method assisted spray drying Download PDF

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CN115403023A
CN115403023A CN202211354117.0A CN202211354117A CN115403023A CN 115403023 A CN115403023 A CN 115403023A CN 202211354117 A CN202211354117 A CN 202211354117A CN 115403023 A CN115403023 A CN 115403023A
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spray drying
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lithium iron
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方明
张公平
曹栋强
龚丽锋
李宜薄
郝培栋
王博
吴青
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Zhejiang Gepai Cobalt Industry New Material Co ltd
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Abstract

The invention relates to the field of lithium ion battery anode materials, and provides a novel lithium manganese iron phosphate synthesis route, namely a supercritical hydrothermal method is adopted to assist spray drying to prepare a lithium manganese iron phosphate material. The method comprises the following synthetic steps: 1) Supercritical hydrothermal synthesis reaction: dissolving a phosphorus source, an iron source and a manganese source in water, transferring the mixture into a reactor for reaction, and treating a resultant to obtain ferrous manganese phosphate precursor powder; 2) Grinding by a sand mill: dissolving manganese ferrous phosphate powder, a lithium source, a supplementary phosphorus source and a carbon source in pure water, and grinding by using a sand mill; 3) Spray drying: spray drying the feed liquid under a set condition to obtain a lithium iron manganese phosphate precursor; 4) And (3) high-temperature sintering: and sintering, crushing, sieving and demagnetizing the powder obtained by spray drying to obtain the spherical carbon-coated lithium manganese iron phosphate cathode material. The method disclosed by the invention is simple in process, rapid and efficient, and uniform in particle morphology, and finally the spherical carbon-coated lithium manganese iron phosphate material with excellent electrochemical properties is obtained.

Description

Method for preparing lithium iron manganese phosphate by supercritical hydrothermal method assisted spray drying
Technical Field
The invention relates to a preparation method of a lithium ion battery anode material, in particular to a method for preparing a lithium iron manganese phosphate anode material by spray drying assisted by a supercritical hydrothermal method.
Background
Olivine phosphate-based positive electrode material LiMPO 4 Compared with the layered positive electrode material, the layered positive electrode material (M = Fe, mn, co, ni and the like) has the advantages of stable structure, cost effectiveness, environmental friendliness and the like, and becomes a research hotspot of the positive electrode material of the lithium ion power battery. Lithium iron phosphate (LiFePO) 4 ) Although the most mature positive electrode material in the phosphate compounds is commercialized in a large scale, the low discharge plateau (3.4V) limits further development in the process of increasing the requirements on the battery. In the olivine type LiMPO 4 In family, lithium iron manganese phosphate material LiFe x Mn 1-x PO 4 (LMFP) combines the stable electrochemical performance of lithium iron phosphate and the high voltage advantage of lithium manganese phosphate, gives consideration to high energy density and high safety, and meanwhile, the voltage platform of the lithium iron phosphate can be adapted to conventional electrolyte, so that a chance is provided for the lithium iron phosphate to cut into the market.
Currently, liMn 1-x Fe x PO 4 The material can be prepared by a solid phase method and a liquid phase method. The solid phase method is the most traditional method, the equipment and the process are relatively simple, the method is beneficial to batch production, but the synthesis temperature is high, the synthesis time is long, the granularity and the distribution of the product are not easy to control, the uniformity is poor, and the ideal electrochemical performance is difficult to obtain. Patent publication No. CN103280579AThe synthesis steps mainly comprise the steps of iron oxide raw material refining and activation, precursor preparation, presintering, coarse crushing, sintering and the like, and the synthesized lithium manganese iron phosphate product has poor consistency and uneven particle morphology, and generates more waste gas pollution in the whole high-temperature solid-phase reaction process. The liquid phase method has better product consistency, is easier to form uniform solid solution, and relieves the problems of manganese dissolution and the like. The most common liquid phase manufacturing method at present is to form a ferromanganese phosphate intermediate first and then add a lithium source to prepare the lithium iron manganese phosphate. For example, in patent publication No. CN104518217A, manganese source, iron source, and phosphorus source are placed in a reaction vessel, surfactant and nitric acid are added under liquid phase condition to adjust pH of the system, and oxidation-coprecipitation reaction under hydrothermal condition is performed to prepare Mn x Fe (1-x) PO 4 ·yH 2 And O. In the preparation process of the manganese iron phosphate precursor, due to Mn 3+ Unstable and strong oxidizing property, and Mn with theoretical stoichiometric ratio is difficult to obtain by a synthetic method 1-x Fe x PO 4 The material is easy to generate impure phases, the preparation process is complex, the synthesis period is long, the product is not easy to dry, the industrialization difficulty is high, and the cost is high.
Compared with the traditional hydrothermal synthesis reaction, the reaction rate of the supercritical hydrothermal synthesis technology is high, and the target product can be prepared only within minutes in an experiment. In the continuous operation process, the residence time of the reaction liquid is short, the overgrowth of crystal grains can be inhibited, the particle size distribution width of the synthesized superfine particles is narrow, and the particle shape is uniform. By virtue of the characteristics of high speed, high efficiency and controllable conditions, the continuous supercritical hydrothermal synthesis method plays an important role in the research 23428of preparing ultrafine particles.
Therefore, the patent provides a new synthesis route, a ferromanganese precursor is synthesized by a supercritical hydrothermal synthesis method, and the ferromanganese precursor and a lithium source are ground by a sand mill and then are subjected to spray drying to prepare the micron-sized spherical lithium manganese iron phosphate material. The precursor obtained by the synthetic route can achieve atomic-level mixing, simplify subsequent treatment processes and meet the requirements of industrial large-scale production. At present, research on preparing the lithium iron manganese phosphate anode material by using a supercritical hydrothermal method to assist spray drying is not found.
Disclosure of Invention
The invention provides a new route for synthesizing a lithium iron manganese phosphate anode material, which is characterized in that a supercritical hydrothermal synthesis method is adopted to synthesize a manganese iron phosphate precursor which is uniformly mixed at an atomic level, and then spray drying is carried out to obtain a spherical lithium iron manganese phosphate anode material with uniform appearance.
In order to achieve the purpose, the invention designs a method for preparing lithium iron manganese phosphate by using a supercritical hydrothermal method to assist spray drying, which comprises the following steps:
s1, supercritical hydrothermal synthesis reaction: preparing a mixed solution from an iron source and a manganese source by using deionized water, adding an antioxidant, uniformly mixing a raw material solution, transferring the mixed solution into a raw material kettle L1, independently preparing a phosphorus source into a solution, transferring the solution into a raw material kettle L2, respectively pumping the solutions in the raw material kettles L1 and L2 into a mixer by using a high-pressure pump for premixing, and transferring the deionized water into a preheater; feeding the materials into a reactor for continuous synthesis reaction, cooling the materials to room temperature in a cooling tank, and performing suction filtration, drying and calcination on the obtained slurry to obtain the anhydrous manganese ferrous phosphate (Fe) x Mn y ) 3 (PO 4 ) 2 A precursor;
s2, mixing materials by using a sand mill: dissolving the ferrous manganese phosphate, the lithium source, the supplementary phosphorus source and the carbon source obtained in the step S1 in pure water, and grinding by using a sand mill to obtain slurry;
s3, spray drying: carrying out spray drying on the S2 feed liquid to obtain a lithium iron manganese phosphate precursor;
s4, high-temperature sintering: compacting the spray-dried lithium manganese iron phosphate precursor powder, calcining under the protection of inert gas, naturally cooling to room temperature, performing jet milling, sieving with a 400-mesh screen, and demagnetizing to obtain a carbon-coated lithium manganese iron phosphate cathode material;
the chemical general formula LiMn of the lithium iron manganese phosphate cathode material y Fe x PO 4 /C，0.5≤y≤0.8，0.2≤x≤0.5，x+y=1。
Mixing a manganese iron phosphate positive active material, acetylene black as a conductive agent and polyvinylidene fluoride as a binder according to a mass ratio of 90.
The continuous supercritical hydrothermal experimental device comprises a raw material kettle, a filter, a one-way valve, a tubular reaction kettle, an electric heating belt, a circulating water condensing device, a back pressure valve, a manual pump, a buffer tank, a collection kettle, a pressure gauge, a stainless steel pipeline, a thermocouple, a temperature adjusting device and the like. Furthermore, the reaction kettle of the device mainly comprises a heat insulation sleeve, an electric heating rod, a thermocouple, a tubular reactor and the like. The material of the reaction kettle is 316L high-quality stainless steel, the design temperature is 500 ℃, the design pressure is 40MPa, and the design volume is 500mL.
Preferably, in step S1, the parameters of the reactor are set to be heated to 360-460 ℃ and the pressure in the reactor is adjusted to 23-30MPa by a pump.
Preferably, in step S1, a mixed solution with Fe/Mn concentration of 0.8-1.5mol/L is added, 0.5-2g/L of antioxidant is added into the solution, a P source is independently prepared into a 0.5-1.0mol/L solution, the calcination temperature of the manganese iron phosphate precursor is 200-400 ℃, and the calcination time is 2-4h (inert gas is one or more of nitrogen, argon and hydrogen, most preferably, the calcination is performed at 400 ℃ for 2h under high-purity nitrogen).
Preferably, in step S1, a mixed solution having a Fe/Mn concentration of 1mol/L is added to the solution in an amount of 1g/L, and the P source is separately prepared as a 0.66mol/L solution.
Preferably, in step S2, the ratio of Li: mn: fe: P =1.02-1.05 is controlled from 0.5 to 0.8 (most preferably, the molar ratio of the added elements Li: mn: fe: P =1.03 in S2 is controlled from 0.6 to 0.4).
Preferably, in step S2, the rotation speed of the sand mill is set at 2000-3000rpm, the grinding time is 4-8h, the particle diameter D50=0.2-0.3um of the slurry obtained by grinding is controlled, and the solid content of the feed liquid is controlled at 10-40%.
Preferably, in the step S2, the grinding is performed by coarse grinding and then fine grinding, wherein a planetary ball mill is used for the coarse grinding, the rotation speed of the coarse grinding is 300rpm, and the coarse grinding time is 1h; the fine grinding adopts a sand mill, the rotating speed is 2000rpm, the time is 5h, and the granularity of the fine grinding slurry is controlled to be D50=0.2-0.3um.
Preferably, in step S3, the inlet air temperature for spray drying is 150 to 250 ℃, and the outlet air temperature is 70 to 110 ℃ (most preferably, the inlet air temperature is 170 ℃, and the outlet air temperature is 80 ℃).
Preferably, in step S4, the protective atmosphere is selected from inert gases such as nitrogen, helium, argon, etc., and the sintering furnace is sintered for 3-10h at a heating rate of 1-5 ℃/min to 650-800 ℃ (most preferably at a heating rate of 5 ℃/min to 680 ℃, and the temperature is kept for 5 h).
The protective atmosphere is selected from nitrogen, helium, argon, etc., preferably high purity nitrogen (99.999%).
In the invention, the lithium source, the iron source, the manganese source, the phosphorus source and the carbon source are mainly used for synthesizing lithium manganese iron phosphate, and all the materials can be conventional in the field. In a preferred scheme, the iron source is at least one of ferrous sulfate, ferrous chloride and ferrous nitrate solution, and is preferably ferrous sulfate; the manganese source is one or more of manganese chloride, manganese acetate, manganese sulfate and manganese nitrate, and manganese sulfate is preferred; the phosphorus source is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate and diammonium hydrogen phosphate, and is preferably phosphoric acid; the antioxidant is preferably ascorbic acid.
The invention provides a preparation method of a phosphate anode material by liquid-phase synthesis of a ferromanganese precursor and solid-phase sintering. Compared with the prior art, the invention has the following beneficial effects:
1) Due to the unique technical superiority of the supercritical hydrothermal synthesis method (SHS), the method has great development in the preparation research of lithium ion battery materials. The high-quality material with small particle size and uniform particle size distribution can be prepared by adjusting parameters such as temperature, pressure and the like in the reaction process; the raw materials are synthesized very quickly in a reactor with set condition parameters, so that the reaction time is effectively shortened, the energy consumption is reduced, and the production cost is reduced; supercritical water is used as an easily controlled synthetic solvent, and the synthesis reaction of the supercritical water does not cause pollution to the external environment, so that the supercritical water is green and environment-friendly.
2) The manganese iron phosphate precursor synthesized in advance can ensure the uniformity of manganese, iron and phosphorus on a microscopic atomic scale, and effectively ensures the uniformity of the finally synthesized manganese iron phosphate material.
3) By adopting a spray drying mode, the method not only can realize quick drying, but also can finally synthesize the spherical lithium iron manganese phosphate anode material with uniform appearance, and is suitable for industrial large-scale production.
Compared with the prior art, the method for preparing the lithium iron manganese phosphate by using the supercritical hydrothermal method to assist spray drying has the advantages of simple preparation process, low production cost, small influence on environment and suitability for industrial production. The invention is a precursor synthesized in advance, and can avoid the loss of the part participating in the reaction to form lithium sulfate in the hydrothermal process.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed to be used in the description of the embodiments are briefly introduced below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without creative efforts.
FIG. 1 is a schematic diagram of a supercritical hydrothermal synthesis apparatus and pipeline;
fig. 2 is an XRD chart of the spherical carbon-coated lithium manganese iron phosphate cathode material prepared in example 1 of the present invention;
FIG. 3 is an SEM image of a manganese iron phosphate precursor prepared in example 1 of the present invention;
fig. 4 is an SEM image of the spherical carbon-coated lithium manganese iron phosphate positive electrode material prepared in example 1 of the present invention;
fig. 5 is an EDS mapping diagram of the spherical carbon-coated lithium iron manganese phosphate cathode material prepared in example 1 of the present invention, (a) Fe, (b) Mn, (C) P, and (d) C;
FIG. 6 is an SEM image of a manganese iron phosphate precursor prepared in example 5 of the present invention;
FIG. 7 is an SEM image of a carbon-coated lithium iron manganese phosphate positive electrode material prepared by a common solid-phase method in comparative example 2 of the present invention;
fig. 8 is a first-turn charge-discharge curve diagram of the spherical carbon-coated lithium manganese iron phosphate positive electrode material prepared in example 1 of the present invention;
fig. 9 is a 52-turn discharge curve diagram of the spherical carbon-coated lithium manganese iron phosphate cathode material prepared in example 1 of the present invention;
fig. 10 is a graph showing comparison of cycle performance of the positive electrode materials 1C prepared in example 1, comparative example 1 and comparative example 2 of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is further described in detail with reference to the following embodiments.
The supercritical hydrothermal synthesis method adopted in the embodiment of the invention, and the synthesis device and the pipeline schematic diagram are shown in fig. 1.
Example 1
A method for preparing lithium iron manganese phosphate by supercritical hydrothermal method assisted spray drying comprises the following specific steps:
weighing FeSO according to a molar ratio of 0.4 4 ·7H 2 O、MnSO 4 ·H 2 Dissolving O in deionized water to prepare a solution with the metal ion concentration of 1mol/L, adding ascorbic acid according to the concentration of 1g/L, stirring and mixing the raw material solution uniformly, and transferring the raw material solution to a raw material kettle L1; preparing a phosphoric acid solution with the phosphate radical concentration of 0.66mol/L, and transferring the solution into a raw material kettle L2; respectively pumping the solutions in the raw material kettles L1 and L2 into a static mixer for premixing by a high-pressure pump, transferring deionized water into a preheater, transferring the materials from the static mixer into a reactor at a feeding speed of 20mL/min, quickly cooling to room temperature after the reaction (the reaction temperature is 380 ℃ and the reaction pressure is 24 Mpa), carrying out suction filtration, vacuum drying, crushing and compacting on the obtained slurry, and sintering for 2 hours at 400 ℃ under the protection of high-purity nitrogen to obtain dark green slurryPrecursor powder of manganese iron phosphate.
Manganese iron phosphate precursor (Fe) 0.4 Mn 0.6 ) 3 (PO 4 ) 2 Lithium hydroxide LiOH. H 2 Dissolving supplementary phosphorus source phosphoric acid (high-purity phosphoric acid) in pure water according to the proportion of Li: mn: fe: P =1.03 of 0.6 to 0.4, adding cane sugar (the theoretical generated carbon content is 3% of the mass of the lithium manganese iron phosphate), controlling the solid content to be 20%, grinding, performing coarse grinding and then performing fine grinding, wherein a planetary ball mill is used for the coarse grinding, the coarse grinding rotation speed is 300rpm, and the coarse grinding time is 1h; the fine grinding adopts a sand mill with the rotating speed of 2000rpm and the time of 5h, the granularity of the fine grinding slurry is controlled to be D50=0.2-0.3um, the slurry is dried by a spray dryer with the air inlet temperature of 170 ℃ and the air outlet temperature of 80 ℃, and the collected material is compacted in N 2 Calcining at 680 ℃ for 5h under the protection of atmosphere (the temperature of a sintering furnace is raised at the heating rate of 1-5 ℃/min), naturally cooling to room temperature, crushing by using a jet mill, sieving by using a 400-mesh sieve, and demagnetizing to obtain LiMn 0.6 Fe 0.4 PO 4 And C, a positive electrode material.
The XRD pattern of the lithium iron manganese phosphate prepared in this example is shown in fig. 2, from which it can be seen that the main peaks both can be matched with olivine-type lithium iron phosphate, and no other impurity phases are generated. As shown in FIG. 3, the morphology of the manganese iron phosphate precursor is a nanoparticle aggregate, and the primary particle size is small. The morphology of the lithium iron manganese phosphate after spray drying and high-temperature sintering is micron-sized spherical particles shown in fig. 4, and the distribution of elements P, fe, mn and C can be seen to be relatively uniform through an EDS Mapping chart shown in fig. 5.
Fig. 8 is a first-turn charge-discharge curve of the lithium iron manganese phosphate material prepared in example 1 at a rate of 0.2C, the discharge capacity is 156.13mAh/g, and the first-turn coulombic efficiency is 92.1%, and fig. 9 is a 52-turn charge-discharge curve graph of the lithium iron manganese phosphate material prepared in example 1 actually measured by a novei tester, it can be seen that the coincidence degree of the discharge curve at a rate of 1C is high, which indicates that the cycle stability of the material is good.
Examples 2 to 5
When supercritical water is used as a reaction medium, temperature and pressure are key parameters for controlling the reaction and crystallization processes, and the experimental scheme is similar to that of example 1, and examples 2 to 5 change the temperature and pressure parameters in the supercritical hydrothermal synthesis process, as shown in table 1.
Fig. 6 shows that the manganese iron phosphate precursor prepared in example 5 has two morphologies, i.e., bulk and granular, and Mn and Fe are in respective phases, which results in a decrease in electrochemical performance of the finally prepared lithium iron manganese phosphate.
Examples 6 to 9
In examples 6 to 9, the molar ratio of Fe to Mn in the metal salt solution was changed, and the other experimental designs were the same as in example 1, thereby preparing spherical lithium manganese iron phosphate with different manganese-iron ratios.
TABLE 1
Figure 714058DEST_PATH_IMAGE001
Comparative example 1
A carbon-free coated spherical lithium manganese iron phosphate cathode material.
According to the experimental scheme of the embodiment 1, the carbon-free coated lithium iron manganese phosphate cathode material can be obtained only by removing sucrose as a conductive carbon source.
Comparative example 2
The carbon-coated lithium iron manganese phosphate anode material is prepared by a common solid phase method.
Weighing Fe according to the molar ratio of Li to Mn to Fe to P =1.03 2 O 3 、Mn 3 O 4 、H 3 PO 4 And LiOH are dissolved in deionized water, and a certain amount of sucrose is added (the addition amount of the sucrose takes the theoretical residual carbon amount as the reaction product LiMn x Fe y PO 4 3%) and solid content is controlled at 20%, grinding for 5h by a sand mill at 2000rpm, controlling the feed liquid D50 to be less than or equal to 300nm, drying at 90 ℃, and crushing to obtain a yellow precursor. Sintering at 680 deg.C for 5h under the protection of high-purity nitrogen, naturally cooling to room temperature, jet-milling, sieving, and removing magnetism to obtain gray black LiMn y Fe x PO 4/ And C, a positive electrode material.
Fig. 7 is an SEM image of the lithium iron manganese phosphate material prepared by the general solid phase method used in comparative example 2, and it can be seen that the particle size is not uniform and there is a significant agglomeration phenomenon.
After the assembled battery is kept stand for 4 hours, the button cells prepared in the examples and the comparative examples are tested by using a novyi tester, the voltage range is 2.0V-4.5V, the button cells are activated for 2 circles at 0.2C, then the button cells are cycled for 50 circles at 1C current, and the electrochemical performance test is carried out, and the test results are listed in Table 2.
TABLE 2
Figure 821691DEST_PATH_IMAGE002
As can be seen from the data in the above table, by optimizing the temperature and pressure parameters in the supercritical hydrothermal synthesis process, and performing subsequent treatment on the precursor prepared under the optimal conditions, the first charge-discharge efficiency of the finally prepared spherical carbon-coated lithium manganese phosphate at 0.2C is 92.1%, and the capacity retention rate after 50 cycles of 1C cycle is as high as 97.10%, which is much higher than that of the carbon-coated lithium manganese phosphate material prepared by ordinary solid phase sintering, fig. 10 shows that the cycle performance comparison of the materials obtained in example 1, comparative example 1 and comparative example 2 at 1C magnification shows that the capacity and cycle stability of the lithium manganese phosphate material prepared by supercritical hydrothermal synthesis method assisted spray drying are much higher than those of the material prepared by solid phase method, because the particle size and distribution of the product are not easy to control, uniform distribution of iron and manganese on the microstructure is difficult to realize, dissolution of manganese is difficult to avoid in the cycle process, and the electrochemical performance is poor. The lithium iron manganese phosphate materials with different components are obtained by changing the proportion of ferromanganese, and the electrochemical performance of the materials is reduced along with the increase of Mn doping amount, because the possibility of Mn dissolution in the circulating process is increased along with the increase of Mn content; and secondly, the conductivity of the material is reduced due to the increase of the manganese content, so that the exertion of the electrochemical performance of the whole material is influenced.
The above description is intended to be illustrative of the preferred embodiment of the present invention and should not be taken as limiting the invention, but rather, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Claims (10)

1. A method for preparing lithium iron manganese phosphate by using a supercritical hydrothermal method to assist spray drying is characterized by comprising the following steps:
s1, supercritical hydrothermal synthesis reaction: preparing a mixed solution from an iron source and a manganese source by using deionized water, adding an antioxidant, uniformly mixing a raw material solution, transferring the mixed solution into a raw material kettle L1, independently preparing a phosphorus source into a solution, transferring the solution into a raw material kettle L2, respectively pumping the solutions in the raw material kettles L1 and L2 into a mixer by using a high-pressure pump for premixing, and transferring the deionized water into a preheater; feeding the materials into a reactor for continuous synthesis reaction, cooling the materials to room temperature in a cooling tank, and performing suction filtration, drying and calcination on the obtained slurry to obtain the anhydrous manganese ferrous phosphate (Fe) x Mn y ) 3 (PO 4 ) 2 A precursor;
s2, mixing materials by using a sand mill: dissolving the ferrous manganese phosphate, the lithium source, the supplementary phosphorus source and the carbon source obtained in the step S1 in pure water, and grinding by using a sand mill to obtain slurry;
s3, spray drying: carrying out spray drying on the S2 feed liquid to obtain a lithium iron manganese phosphate precursor;
s4, high-temperature sintering: compacting the spray-dried lithium manganese iron phosphate precursor powder, calcining under the protection of inert gas, naturally cooling to room temperature, performing jet milling, sieving by a 400-mesh sieve, and demagnetizing to obtain a carbon-coated lithium manganese iron phosphate positive electrode material;
the chemical general formula LiMn of the lithium iron manganese phosphate cathode material y Fe x PO 4 /C，0.5≤y≤0.8，0.2≤x≤0.5，x+y=1。
2. The method for preparing lithium iron manganese phosphate by using the supercritical hydrothermal method to assist spray drying as claimed in claim 1, which is characterized in that: in step S1, the parameters of the reactor are set to be heated to 360-460 ℃, and the pressure in the reactor is adjusted to 23-30MPa by a pump.
3. The supercritical hydrothermal method-assisted spray drying method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: in the step S1, the calcination temperature of the manganese ferrous phosphate precursor is 200-400 ℃, and the calcination time is 2-4h.
4. The supercritical hydrothermal method-assisted spray drying method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: in step S1, a mixed solution with the concentration of Fe/Mn of 0.8-1.5mol/L is added with 0.5-2g/L of antioxidant, and a P source is independently prepared into a solution with the concentration of 0.5-1.0 mol/L.
5. The supercritical hydrothermal method assisted spray drying method for preparing lithium iron manganese phosphate according to claim 4, characterized in that: in step S1, a mixed solution having a Fe/Mn concentration of 1mol/L was added to the solution at a concentration of 1g/L with an antioxidant, and a P source alone was prepared as a 0.66mol/L solution.
6. The supercritical hydrothermal method-assisted spray drying method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: in the step S2, the ratio of Li to Mn to Fe to P =1.02-1.05 is controlled in a range from 0.5 to 0.8.
7. The supercritical hydrothermal method-assisted spray drying method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: in step S2, the rotation speed of the sand mill is set to 2000-3000rpm, the grinding time is 4-8h, the grain diameter D50=0.2-0.3um of the slurry obtained by grinding is controlled, and the solid content of the feed liquid is controlled to be 10-40%.
8. The supercritical hydrothermal method-assisted spray drying method for preparing lithium iron manganese phosphate according to claim 7, characterized in that: in the step S2, the grinding is carried out firstly on coarse grinding and then on fine grinding, wherein a planetary ball mill is adopted for coarse grinding, the rotational speed of the coarse grinding is 300rpm, and the coarse grinding time is 1h; the fine grinding adopts a sand mill, the rotating speed is 2000rpm, the time is 5h, and the granularity of the fine grinding slurry is controlled to be D50=0.2-0.3um.
9. The supercritical hydrothermal method-assisted spray drying method for preparing lithium iron manganese phosphate according to claim 1, characterized in that: in step S3, the inlet air temperature of spray drying is 150-250 ℃, and the outlet air temperature is 70-110 ℃.
10. The method for preparing lithium iron manganese phosphate by using the supercritical hydrothermal method to assist spray drying as claimed in claim 1, which is characterized in that: in step S4, the inert gas is selected from nitrogen, helium and argon, and the sintering furnace is sintered for 3-10h at the temperature rising rate of 1-5 ℃/min to 650-800 ℃.
CN202211354117.0A 2022-11-01 2022-11-01 Method for preparing lithium iron manganese phosphate by supercritical hydrothermal method assisted spray drying Pending CN115403023A (en)

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