CN114380280A - Preparation method of lithium iron manganese phosphate cathode material - Google Patents
Preparation method of lithium iron manganese phosphate cathode material Download PDFInfo
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Abstract
The invention relates to the technical field of lithium batteries, in particular to a preparation method of a lithium iron manganese phosphate positive electrode material. In the preparation process of the lithium iron manganese phosphate cathode material, the nucleation and growth speeds are adjusted by controlling the reactant adding speed, high-speed stirring and temperature control to form uniform nano particles; and then mixing the doping element, a carbon source, ammonium dihydrogen phosphate, lithium carbonate and the iron-manganese compound precipitation precursor, and sintering at high temperature to obtain the element-doped lithium iron manganese phosphate anode material. The particles formed by the coprecipitation method have uniform shape and granularity, and compared with the existing high-energy ball-milling solid-phase method, the method has the advantages of lower energy consumption and high production efficiency.
Description
Technical Field
The invention relates to the technical field of lithium batteries, in particular to a preparation method of a lithium iron manganese phosphate positive electrode material.
Background
At present, the anode materials of lithium batteries can be mainly divided into lithium cobaltate, lithium iron phosphate, lithium manganate, lithium nickelate, ternary materials, lithium manganese iron phosphate and the like. The lithium iron manganese phosphate is an upgraded product of the lithium iron phosphate as a high-voltage (4.1V) phosphate material, and the energy density of the lithium iron manganese phosphate lithium battery can be improved by about 20% compared with that of the lithium iron phosphate battery under the same capacity exertion. Compared with ternary materials, the lithium manganese iron phosphate has similar energy density, but higher safety and lower price, and is expected to become a potential material of a cobalt-free positive electrode material of a new-generation high-energy-density power battery.
However, the existing technology for preparing lithium iron manganese phosphate has high energy consumption and low efficiency; CN104167549A, CN105329867A and CN111276693A utilize an iron source, a manganese source, a phosphorus source, a carbon source and a lithium source to be mixed and then a sand mill to crush particles to a nanometer size; but the energy consumption of the high-energy ball milling solid phase method is high, the production efficiency is low, and the uniformity of the obtained particles is poor.
Disclosure of Invention
In order to solve the above problems, the present invention aims to provide a preparation method of a lithium iron manganese phosphate positive electrode material.
In the aqueous solution, manganese ions and iron ions are firstly combined with a chelating agent to form iron ion and manganese ion chelates, and after a precipitator is dropped, the manganese ions and the iron ions are slowly released from the iron ion and manganese ion chelates to be combined with the precipitator to form an iron-manganese precipitate precursor. The size of the particles of the lithium iron manganese phosphate cathode material is determined by the nucleation speed and the growth speed of the precipitation reaction, the faster the nucleation speed and the slower the growth speed, the smaller the particles are, and conversely, the slower the nucleation speed and the faster the growth speed, the larger the particles are. The rate of addition of each reactant, the rate of stirring, and the reaction temperature determine the nucleation and growth rates. Relative to the iron and manganese ions, the faster the addition speed and the larger the addition amount are, the faster the addition speed of the precipitant is, and the higher the concentration is, the faster the nucleation speed is, and the too fast dropping or the too high concentration can also cause uneven particle size and agglomeration of the particles; the faster the stirring speed and the properly higher the temperature, the faster the nucleation speed. Therefore, the speed of pumping the iron-manganese ion aqueous solution, the chelating agent solution and the precipitator solution into the reaction kettle in the coprecipitation process is reasonably controlled, and the uniformity of the formed nano particles can be effectively improved by the stirring temperature and the temperature of the reaction kettle.
In the preparation process of the lithium iron manganese phosphate anode material, the nucleation and growth speed is adjusted by high-speed stirring and temperature control, so that uniform nano particles are formed. And then mixing the doping element, a carbon source, ammonium dihydrogen phosphate, lithium carbonate and the iron-manganese precipitation precursor, and sintering at high temperature to obtain the element-doped lithium iron manganese phosphate anode material. The particles formed by the coprecipitation method have uniform shape and granularity, and compared with the existing high-energy ball-milling solid phase method, the method has the advantages of lower energy consumption and high production efficiency.
The purpose of the invention can be realized by the following technical scheme:
the invention aims to provide a preparation method of a lithium iron manganese phosphate positive electrode material, which comprises the following steps:
(1) respectively preparing a chelating agent base solution, a chelating agent solution, a precipitator solution and a ferro-manganese ion aqueous solution;
(2) pumping the chelating agent base solution, the chelating agent solution and the precipitator solution obtained in the step (1) into a reaction kettle, and reacting to obtain a ferro-manganese precipitate precursor through coprecipitation;
when the capacity of the reaction kettle is 100L, the addition amount of the chelating agent base solution pumped into the reaction kettle is 20L; the pumping speed of the chelating agent solution into the reaction kettle is 0.2-6L/h; the pumping speed of the precipitant solution into the reaction kettle is 5-60L/h; the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 0.5-6L/h;
(3) uniformly mixing the iron-manganese precipitate precursor obtained in the step (2) with a lithium source, a phosphorus source, a carbon source and a solvent, and drying to obtain a manganese-iron-lithium phosphate mixture;
(4) and (4) pressing the lithium iron manganese phosphate mixture obtained in the step (3) into tablets, and sintering to obtain the lithium iron manganese phosphate anode material.
In one embodiment of the invention, in the step (1), the base solution of the chelating agent is an aqueous solution of the chelating agent with the concentration of 0.1-2.0 mol/L; the chelating agent solution is a chelating agent water solution with the concentration of 0.1-2.0 mol/L.
In one embodiment of the present invention, in the step (1), the chelating agent is selected from one or more of citric acid, sodium citrate, EDTA, salicylic acid or sulfosalicylic acid;
the precipitant solution is sodium oxalate solution or sodium hydroxide solution;
the iron-manganese ion aqueous solution is a mixed solution obtained by dissolving an iron source and a manganese source in deionized water; the iron source is selected from one or more of ferric nitrate, ferric acetate, ferrous sulfate or ferrous chloride; the manganese source is selected from one or more of manganese acetate, manganese sulfate or manganese nitrate;
adding all the base solution of the chelating agent into a reaction kettle before reaction; the chelating agent solution is pumped into a reaction kettle in the reaction process.
In one embodiment of the invention, the total concentration of the iron source and the manganese source in the iron-manganese ion aqueous solution is 0.2-2.0 mol/L; the molar ratio of the iron source to the manganese source is 2: 8-7: 3; the concentration of the precipitant solution is 0.1-0.3 mol/L.
In one embodiment of the present invention, in the step (2), the rotation speed of the reaction kettle is 500-.
In one embodiment of the present invention, in the step (3), the lithium source is one or more selected from lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, lithium nitrate, lithium oxalate or lithium acetate;
the phosphorus source is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or lithium dihydrogen phosphate;
the carbon source is selected from one or more of sucrose, glucose, fructose, lactose, citric acid or starch;
the solvent is selected from one or more of pure water, ethanol, propanol or acetone.
In one embodiment of the present invention, in the step (3), the molar ratio of the lithium source to the iron source and the manganese source is 1.0 to 1.3: 1; the mol ratio of the phosphorus source to the iron source and the manganese source is 1.0-1.3: 1; the carbon source accounts for 1-10 wt% of the lithium iron manganese phosphate mixture; the solvent accounts for 1-20 wt% of the lithium iron manganese phosphate mixture.
In one embodiment of the present invention, in the step (3), the drying temperature is 60 to 120 ℃ and the drying time is 12 hours during the drying process.
In one embodiment of the invention, in the step (4), protective gas is introduced during the sintering process, and the sintering process is progressive heating sintering, and has 3 sections;
the protective gas is one or more of nitrogen, argon and helium.
In one embodiment of the invention, in the first stage of sintering process, the sintering temperature is 100-300 ℃, and the sintering time is 1-5 h; in the second-stage sintering process, the sintering temperature is 300-500 ℃, and the sintering time is 1-5 h; in the third stage of sintering process, the sintering temperature is 650-700 ℃, and the sintering time is 8-14 h.
Compared with the prior art, the invention has the following beneficial effects:
(1) the manganese lithium iron phosphate cathode material prepared by the method has good uniformity of nano particles and high production efficiency;
(2) the lithium iron manganese phosphate anode material prepared by the method has high charge-discharge specific capacity.
Drawings
Fig. 1 is an electron microscope image of a lithium iron manganese phosphate positive electrode material obtained in example 1 of the present invention;
fig. 2 is a charge-discharge specific capacity characteristic curve diagram of the lithium iron manganese phosphate positive electrode material obtained in embodiment 1 of the present invention.
Detailed Description
The invention provides a preparation method of a lithium iron manganese phosphate anode material, which comprises the following steps:
(1) respectively preparing a chelating agent base solution, a chelating agent solution, a precipitator solution and a ferro-manganese ion aqueous solution;
(2) pumping the chelating agent base solution, the chelating agent solution and the precipitator solution obtained in the step (1) into a reaction kettle, and reacting to obtain a ferro-manganese precipitate precursor through coprecipitation;
when the capacity of the reaction kettle is 100L, the addition amount of the chelating agent base solution pumped into the reaction kettle is 20L; the pumping speed of the chelating agent solution into the reaction kettle is 0.2-6L/h; the pumping speed of the precipitant solution into the reaction kettle is 5-60L/h; the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 0.5-6L/h;
(3) uniformly mixing the iron-manganese precipitate precursor obtained in the step (2) with a lithium source, a phosphorus source, a carbon source and a solvent, and drying to obtain a manganese-iron-lithium phosphate mixture;
(4) and (4) pressing the lithium iron manganese phosphate mixture obtained in the step (3) into tablets, and sintering to obtain the lithium iron manganese phosphate anode material.
In one embodiment of the invention, in the step (1), the base solution of the chelating agent is an aqueous solution of the chelating agent with the concentration of 0.1-2.0 mol/L; the chelating agent solution is a chelating agent water solution with the concentration of 0.1-2.0 mol/L.
In one embodiment of the present invention, in the step (1), the chelating agent is selected from one or more of citric acid, sodium citrate, EDTA, salicylic acid or sulfosalicylic acid;
the precipitant solution is sodium oxalate solution or sodium hydroxide solution;
the iron-manganese ion aqueous solution is a mixed solution obtained by dissolving an iron source and a manganese source in deionized water; the iron source is selected from one or more of ferric nitrate, ferric acetate, ferrous sulfate or ferrous chloride; the manganese source is selected from one or more of manganese acetate, manganese sulfate or manganese nitrate;
adding all the base solution of the chelating agent into a reaction kettle before reaction; the chelating agent solution is pumped into a reaction kettle in the reaction process.
In one embodiment of the invention, the total concentration of the iron source and the manganese source in the iron-manganese ion aqueous solution is 0.2-2.0 mol/L; the molar ratio of the iron source to the manganese source is 2: 8-7: 3; the concentration of the precipitant solution is 0.1-0.3 mol/L.
In one embodiment of the present invention, in the step (2), the rotation speed of the reaction kettle is 500-.
In one embodiment of the present invention, in the step (3), the lithium source is one or more selected from lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, lithium nitrate, lithium oxalate or lithium acetate;
the phosphorus source is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or lithium dihydrogen phosphate;
the carbon source is selected from one or more of sucrose, glucose, fructose, lactose, citric acid or starch;
the solvent is selected from one or more of pure water, ethanol, propanol or acetone.
In one embodiment of the present invention, in the step (3), the molar ratio of the lithium source to the iron source and the manganese source is 1.0 to 1.3: 1; the mol ratio of the phosphorus source to the iron source and the manganese source is 1.0-1.3: 1; the carbon source accounts for 1-10 wt% of the lithium iron manganese phosphate mixture; the solvent accounts for 1-20 wt% of the lithium iron manganese phosphate mixture.
In one embodiment of the present invention, in the step (3), the drying temperature is 60 to 120 ℃ and the drying time is 12 hours during the drying process.
In one embodiment of the invention, in the step (4), protective gas is introduced during the sintering process, and the sintering process is progressive heating sintering, and has 3 sections;
the protective gas is one or more of nitrogen, argon and helium.
In one embodiment of the invention, in the first stage of sintering process, the sintering temperature is 100-300 ℃, and the sintering time is 1-5 h; in the second-stage sintering process, the sintering temperature is 300-500 ℃, and the sintering time is 1-5 h; in the third stage of sintering process, the sintering temperature is 650-700 ℃, and the sintering time is 8-14 h.
The invention is described in detail below with reference to the figures and specific embodiments.
The various starting materials used in the examples are all commercially available unless otherwise specified.
Example 1
The embodiment provides a preparation method of a lithium iron manganese phosphate positive electrode material.
(1) Solution preparation: preparing a mixed aqueous solution (iron-manganese ion aqueous solution) of ferrous sulfate and manganese sulfate, wherein the total concentration of Fe elements and Mn elements is 1.0mol/L, and the molar ratio of the Fe elements to the Mn elements is 3: 7. 0.2mol/L citric acid aqueous solution is prepared as the base solution of the chelating agent. 1.0mol/L citric acid solution is prepared as a chelating agent solution. 0.2mo/L of sodium oxalate aqueous solution is prepared to be used as a precipitator solution.
(2) Synthesizing a ferro-manganese precipitate precursor: the amount of the citric acid bottom liquid in a 100L reaction kettle is 20L, the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 3L/h, the pumping speed of the precipitator solution into the reaction kettle is 15L/h, and the pumping speed of the chelating agent solution into the reaction kettle is 1.5L/h. The rotating speed of the reaction kettle is 2000 r/min, the temperature of the reaction kettle is 60 ℃, the precipitated product is filtered after 4 hours of reaction, the filtered product is washed by deionized water, and then the filtered product is baked at 110 ℃ for 12 hours to remove water, so that a ferro-manganese precipitate precursor is obtained: and (3) iron manganese oxalate precursor.
(3) Uniformly mixing the iron and manganese oxalate precursor, lithium carbonate, ammonium dihydrogen phosphate, glucose and ethanol by using a high-speed mixer, and drying at 90 ℃ for 12 hours to obtain a lithium iron manganese phosphate mixture. Wherein the molar ratio of the Li element to the Fe-Mn element is 1.02: 1, the molar ratio of phosphorus element to iron-manganese element is 1.0: 1, the glucose accounts for 5 percent of the total amount of the powder, and the ethanol accounts for 10 percent of the total amount of the powder.
(4) Pressing the lithium iron manganese phosphate mixture into tablets, and then introducing nitrogen for sintering, wherein in the first-stage sintering process, the sintering temperature is 300 ℃, and the sintering time is 2 hours; in the second stage of sintering process, the sintering temperature is 500 ℃, and the sintering time is 3 hours; in the third stage of sintering process, the sintering temperature is 700 ℃, and the sintering time is 10 h. And then crushing and sieving the material by using a ball mill to obtain the lithium iron manganese phosphate anode material.
As shown in fig. 1, SEM shows that the primary particles of the lithium iron manganese phosphate material are about 100nm, and the particles are uniformly distributed.
As shown in FIG. 2, the lithium iron manganese phosphate anode material has a specific discharge capacity of 148mAh/g and a first efficiency of 97%, showing that Fe3+/Fe2+And Mn3+/Mn2+Two voltage plateaus for redox conversion.
Example 2
The embodiment provides a preparation method of a lithium iron manganese phosphate positive electrode material.
(1) Solution preparation: preparing a mixed aqueous solution of ferrous sulfate and manganese sulfate, wherein the total concentration of Fe and Mn elements is 0.2mol/L, and the molar ratio of the Fe element to the Mn element is 2: 3. 0.1mol/L citric acid aqueous solution is prepared as the base solution of the chelating agent. 0.1mol/L citric acid solution is prepared as a chelating agent solution. 0.24mo/L of sodium oxalate aqueous solution is prepared to be used as a precipitator solution.
(2) Synthesizing a ferro-manganese precipitate precursor: the amount of the citric acid bottom liquid in a 100L reaction kettle is 20L, the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 6L/h, the pumping speed of the precipitator solution into the reaction kettle is 5L/h, and the pumping speed of the chelating agent solution into the reaction kettle is 1.5L/h. The rotating speed of the reaction kettle is 500 r/min, the temperature of the reaction kettle is 25 ℃, the precipitated product is filtered after 6 hours of reaction, the filtered product is washed by deionized water, and then the filtered product is baked at 110 ℃ for 12 hours to remove water, so that a ferro-manganese precipitate precursor is obtained: and (3) iron manganese oxalate precursor.
(3) Uniformly mixing the iron and manganese oxalate precursor, lithium carbonate, ammonium dihydrogen phosphate, glucose and ethanol by using a high-speed mixer, and drying at 60 ℃ for 12 hours to obtain a lithium iron manganese phosphate mixture. Wherein the molar ratio of the Li element to the Fe-Mn element is 1.0: 1, the molar ratio of phosphorus element to iron-manganese element is 1.1: 1, the glucose accounts for 1 percent of the total amount of the powder, and the ethanol accounts for 20 percent of the total amount of the powder.
(4) Pressing the lithium iron manganese phosphate mixture into tablets, and then introducing nitrogen for sintering, wherein in the first-stage sintering process, the sintering temperature is 100 ℃, and the sintering time is 5 hours; in the second stage of sintering process, the sintering temperature is 300 ℃, and the sintering time is 5 hours; in the third stage of sintering process, the sintering temperature is 650 ℃, and the sintering time is 14 h. And then crushing and sieving the material by using a ball mill to obtain the lithium iron manganese phosphate anode material.
Example 3
The embodiment provides a preparation method of a lithium iron manganese phosphate positive electrode material.
(1) Solution preparation: preparing a mixed aqueous solution of ferrous sulfate and manganese sulfate, wherein the total concentration of Fe and Mn elements is 2.0mol/L, and the molar ratio of the Fe element to the Mn element is 7: 8. 2.0mol/L citric acid aqueous solution is prepared as the base solution of the chelating agent. 2.0mol/L citric acid solution is prepared as a chelating agent solution. 0.1mo/L of sodium oxalate aqueous solution is prepared to be used as a precipitator solution.
(2) Synthesizing a ferro-manganese precipitate precursor: the citric acid bottom liquid amount in a 100L reaction kettle is 20L, the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 0.5L/h, the pumping speed of the precipitator solution into the reaction kettle is 10L/h, and the pumping speed of the chelating agent solution into the reaction kettle is 6L/h. The rotating speed of the reaction kettle is 1000 revolutions per minute, the temperature of the reaction kettle is 70 ℃, the precipitated product is filtered after 5 hours of reaction, the filtered product is washed by deionized water, and then the filtered product is baked at 110 ℃ for 12 hours to remove water, so that a ferro-manganese precipitate precursor is obtained: and (3) iron manganese oxalate precursor.
(3) Uniformly mixing the iron and manganese oxalate precursor, lithium carbonate, ammonium dihydrogen phosphate, glucose and ethanol by using a high-speed mixer, and drying at 120 ℃ for 12 hours to obtain a lithium iron manganese phosphate mixture. Wherein the molar ratio of the Li element to the Fe-Mn element is 1.3: 1, the molar ratio of phosphorus element to iron-manganese element is 1.3: 1, the glucose accounts for 10 percent of the total amount of the powder, and the ethanol accounts for 1 percent of the total amount of the powder.
(4) Pressing the lithium iron manganese phosphate mixture into tablets, and then introducing nitrogen for sintering, wherein in the first-stage sintering process, the sintering temperature is 200 ℃, and the sintering time is 1 h; in the second stage of sintering process, the sintering temperature is 400 ℃, and the sintering time is 1 h; in the third sintering process, the sintering temperature is 675 ℃, and the sintering time is 8 h. And then crushing and sieving the material by using a ball mill to obtain the lithium iron manganese phosphate anode material.
Example 4
The embodiment provides a preparation method of a lithium iron manganese phosphate positive electrode material.
(1) Solution preparation: preparing a mixed aqueous solution of ferrous sulfate and manganese sulfate, wherein the total concentration of Fe and Mn elements is 1.0mol/L, and the molar ratio of the Fe element to the Mn element is 3: 7. 0.2mol/L citric acid aqueous solution is prepared as the base solution of the chelating agent. 1.0mol/L citric acid solution is prepared as a chelating agent solution. 0.3mo/L of sodium oxalate aqueous solution is prepared to be used as a precipitator solution.
(2) Synthesizing a ferro-manganese precipitate precursor: the amount of the citric acid bottom liquid in a 100L reaction kettle is 20L, the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 6L/h, the pumping speed of the precipitator solution into the reaction kettle is 20L/h, and the pumping speed of the chelating agent solution into the reaction kettle is 1.5L/h. The rotating speed of the reaction kettle is 2000 r/min, the temperature of the reaction kettle is 60 ℃, the precipitated product is filtered after 3 hours of reaction, the filtered product is washed by deionized water, and then the filtered product is baked at 110 ℃ for 12 hours to remove water, so that a ferro-manganese precipitate precursor is obtained: and (3) iron manganese oxalate precursor.
(3) Uniformly mixing the iron and manganese oxalate precursor, lithium carbonate, ammonium dihydrogen phosphate, glucose and ethanol by using a high-speed mixer, and drying at 90 ℃ for 12 hours to obtain a lithium iron manganese phosphate mixture. Wherein the molar ratio of the Li element to the Fe-Mn element is 1.02: 1, the molar ratio of phosphorus element to iron-manganese element is 1.0: 1, the glucose accounts for 5 percent of the total amount of the powder, and the ethanol accounts for 10 percent of the total amount of the powder.
(4) Pressing the lithium iron manganese phosphate mixture into tablets, and then introducing nitrogen for sintering, wherein in the first-stage sintering process, the sintering temperature is 300 ℃, and the sintering time is 2 hours; in the second stage of sintering process, the sintering temperature is 500 ℃, and the sintering time is 3 hours; in the third stage of sintering process, the sintering temperature is 700 ℃, and the sintering time is 10 h. And then crushing and sieving the material by using a ball mill to obtain the lithium iron manganese phosphate anode material.
Example 5
The embodiment provides a preparation method of a lithium iron manganese phosphate positive electrode material.
(1) Solution preparation: preparing a mixed aqueous solution of ferrous sulfate and manganese sulfate, wherein the total concentration of Fe and Mn elements is 2.0mol/L, and the molar ratio of the Fe element to the Mn element is 3: 7. 0.2mol/L citric acid aqueous solution is prepared as the base solution of the chelating agent. 1.0mol/L citric acid solution is prepared as a chelating agent solution. 0.1mo/L of sodium oxalate aqueous solution is prepared to be used as a precipitator solution.
(2) Synthesizing a ferro-manganese precipitate precursor: the citric acid bottom liquid amount in a 100L reaction kettle is 20L, the speed of pumping the iron-manganese ion aqueous solution into the reaction kettle is 3L/h, the speed of pumping the precipitator solution into the reaction kettle is 60L/h, and the speed of pumping the chelating agent solution into the reaction kettle is 6L/h. The rotating speed of the reaction kettle is 2000 r/min, the temperature of the reaction kettle is 60 ℃, the precipitated product is filtered after 1 hour of reaction, the filtered product is washed by deionized water, and then the filtered product is baked at 110 ℃ for 12 hours to remove water, so that a ferro-manganese precipitate precursor is obtained: and (3) iron manganese oxalate precursor.
(3) Uniformly mixing the iron and manganese oxalate precursor, lithium carbonate, ammonium dihydrogen phosphate, glucose and ethanol by using a high-speed mixer, and drying at 90 ℃ for 12 hours to obtain a lithium iron manganese phosphate mixture. Wherein the molar ratio of the Li element to the Fe-Mn element is 1.02: 1, the molar ratio of phosphorus element to iron-manganese element is 1.0: 1, the glucose accounts for 5 percent of the total amount of the powder, and the ethanol accounts for 10 percent of the total amount of the powder.
(4) Pressing the lithium iron manganese phosphate mixture into tablets, and then introducing nitrogen for sintering, wherein in the first-stage sintering process, the sintering temperature is 300 ℃, and the sintering time is 2 hours; in the second stage of sintering process, the sintering temperature is 500 ℃, and the sintering time is 3 hours; in the third stage of sintering process, the sintering temperature is 700 ℃, and the sintering time is 10 h. And then crushing and sieving the material by using a ball mill to obtain the lithium iron manganese phosphate anode material.
The embodiments described above are described to facilitate an understanding and use of the invention by those skilled in the art. It will be readily apparent to those skilled in the art that various modifications to these embodiments may be made, and the generic principles described herein may be applied to other embodiments without the use of the inventive faculty. Therefore, the present invention is not limited to the above embodiments, and those skilled in the art should make improvements and modifications within the scope of the present invention based on the disclosure of the present invention.
Claims (10)
1. The preparation method of the lithium iron manganese phosphate cathode material is characterized by comprising the following steps of:
(1) respectively preparing a chelating agent base solution, a chelating agent solution, a precipitator solution and a ferro-manganese ion aqueous solution;
(2) pumping the chelating agent base solution, the chelating agent solution and the precipitator solution obtained in the step (1) into a reaction kettle, and reacting to obtain a ferro-manganese precipitate precursor through coprecipitation;
when the capacity of the reaction kettle is 100L, the addition amount of the chelating agent base solution pumped into the reaction kettle is 20L; the pumping speed of the chelating agent solution into the reaction kettle is 0.2-6L/h; the pumping speed of the precipitant solution into the reaction kettle is 5-60L/h; the pumping speed of the iron-manganese ion aqueous solution into the reaction kettle is 0.5-6L/h;
(3) uniformly mixing the iron-manganese precipitate precursor obtained in the step (2) with a lithium source, a phosphorus source, a carbon source and a solvent, and drying to obtain a manganese-iron-lithium phosphate mixture;
(4) and (4) pressing the lithium iron manganese phosphate mixture obtained in the step (3) into tablets, and sintering to obtain the lithium iron manganese phosphate anode material.
2. The preparation method of the lithium iron manganese phosphate cathode material according to claim 1, wherein in the step (1), the base solution of the chelating agent is an aqueous solution of the chelating agent with a concentration of 0.1-2.0 mol/L; the chelating agent solution is a chelating agent water solution with the concentration of 0.1-2.0 mol/L.
3. The preparation method of the lithium iron manganese phosphate cathode material according to claim 1, wherein in the step (1), the chelating agent is one or more selected from citric acid, sodium citrate, EDTA, salicylic acid or sulfosalicylic acid;
the precipitant solution is sodium oxalate solution or sodium hydroxide solution;
the iron-manganese ion aqueous solution is a mixed solution obtained by dissolving an iron source and a manganese source in deionized water; the iron source is selected from one or more of ferric nitrate, ferric acetate, ferrous sulfate or ferrous chloride; the manganese source is selected from one or more of manganese acetate, manganese sulfate or manganese nitrate;
adding all the base solution of the chelating agent into a reaction kettle before reaction; the chelating agent solution is pumped into a reaction kettle in the reaction process.
4. The method for preparing the lithium iron manganese phosphate cathode material according to claim 3, wherein the total concentration of an iron source and a manganese source in the iron-manganese ion aqueous solution is 0.2-2.0 mol/L; the molar ratio of the iron source to the manganese source is 2: 8-7: 3; the concentration of the precipitant solution is 0.1-0.3 mol/L.
5. The method for preparing the lithium iron manganese phosphate cathode material as claimed in claim 1, wherein in the step (2), the rotation speed of the reaction kettle is 500-2000 rpm and the temperature of the reaction kettle is 25-70 ℃.
6. The method for preparing the lithium iron manganese phosphate cathode material according to claim 1, wherein in the step (3), the lithium source is one or more selected from lithium carbonate, lithium hydroxide, lithium dihydrogen phosphate, dilithium hydrogen phosphate, lithium nitrate, lithium oxalate and lithium acetate;
the phosphorus source is selected from one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate or lithium dihydrogen phosphate;
the carbon source is selected from one or more of sucrose, glucose, fructose, lactose, citric acid or starch;
the solvent is selected from one or more of pure water, ethanol, propanol or acetone.
7. The method for preparing the lithium iron manganese phosphate cathode material according to claim 1, wherein in the step (3), the molar ratio of the lithium source to the iron source to the manganese source is 1.0-1.3: 1; the mol ratio of the phosphorus source to the iron source and the manganese source is 1.0-1.3: 1; the carbon source accounts for 1-10 wt% of the lithium iron manganese phosphate mixture; the solvent accounts for 1-20 wt% of the lithium iron manganese phosphate mixture.
8. The preparation method of the lithium iron manganese phosphate cathode material as claimed in claim 1, wherein in the step (3), the drying temperature is 60-120 ℃ and the drying time is 12h in the drying process.
9. The preparation method of the lithium iron manganese phosphate cathode material according to claim 1, wherein in the step (4), protective gas is introduced during sintering, and the sintering process is progressive heating sintering, and has 3 stages;
the protective gas is one or more of nitrogen, argon and helium.
10. The method for preparing the lithium iron manganese phosphate cathode material as claimed in claim 9, wherein in the first stage of sintering, the sintering temperature is 100-300 ℃, and the sintering time is 1-5 h; in the second-stage sintering process, the sintering temperature is 300-500 ℃, and the sintering time is 1-5 h; in the third stage of sintering process, the sintering temperature is 650-700 ℃, and the sintering time is 8-14 h.
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