WO2024027085A1 - 一种固相包覆法制备磷酸锰铁锂的方法 - Google Patents

一种固相包覆法制备磷酸锰铁锂的方法 Download PDF

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WO2024027085A1
WO2024027085A1 PCT/CN2022/141941 CN2022141941W WO2024027085A1 WO 2024027085 A1 WO2024027085 A1 WO 2024027085A1 CN 2022141941 W CN2022141941 W CN 2022141941W WO 2024027085 A1 WO2024027085 A1 WO 2024027085A1
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temperature
manganese phosphate
lithium iron
ball mill
iron manganese
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PCT/CN2022/141941
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English (en)
French (fr)
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王勤
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湖北万润新能源科技股份有限公司
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/362—Composites
    • H01M4/366—Composites as layered products
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/36—Selection of substances as active materials, active masses, active liquids
    • H01M4/58—Selection of substances as active materials, active masses, active liquids of inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy; of polyanionic structures, e.g. phosphates, silicates or borates
    • H01M4/5825—Oxygenated metallic salts or polyanionic structures, e.g. borates, phosphates, silicates, olivines
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/62—Selection of inactive substances as ingredients for active masses, e.g. binders, fillers
    • H01M4/624—Electric conductive fillers
    • H01M4/625—Carbon or graphite
    • 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

Definitions

  • the invention belongs to the field of material technology, and specifically relates to a method for preparing lithium iron manganese phosphate by a solid phase coating method.
  • the conventional lithium iron manganese phosphate carbon coating process is to use inorganic carbon sources to be directly mechanically mixed or to use water-soluble organic matter after drying and high-temperature decomposition and carbonization to achieve carbon coating.
  • the coating of inorganic carbon sources has uneven coating.
  • the coating of organic carbon sources requires spray drying and other processes, which consumes a lot of energy.
  • every ton of lithium iron manganese phosphate is spray dried, so The required cost is 1,000 to 1,200 yuan. If the annual output of lithium iron manganese phosphate is 10,000 tons, the cost for this step alone is 10 million to 12 million.
  • the price of large-scale spray drying equipment is relatively high. The value of the spray drying equipment required to produce 10,000 tons of lithium iron manganese phosphate annually reaches more than 10 million.
  • the technical problem to be solved by the present invention is to provide a method for preparing lithium iron manganese phosphate by a solid phase coating method.
  • the present invention adopts a solid phase coating method to prepare lithium iron manganese phosphate, which can significantly reduce costs. , reduce equipment investment, shorten the process, and at the same time the coating effect is good.
  • the invention provides a method for preparing lithium iron manganese phosphate by a solid phase coating method, which includes the following steps:
  • the mixture is calcined to obtain carbon-coated lithium iron manganese phosphate.
  • the lithium iron manganese phosphate is prepared according to the following method:
  • reaction gas After the iron powder, manganese powder, cerium hydroxide, phosphoric acid and lithium carbonate are mixed and reacted for a period of time, the reaction gas is led out, and then a high-temperature and high-pressure reaction is performed to obtain the reaction product;
  • the reaction product is cooled, iron removed and dried to obtain lithium iron manganese phosphate.
  • the molar ratio of the iron powder, manganese powder to cerium hydroxide, phosphoric acid and lithium carbonate is 1 ⁇ 2:8 ⁇ 9:0.03 ⁇ 0.06:10 ⁇ 13:5.05 ⁇ 5.1.
  • the duration of the reaction is 15 to 30 minutes;
  • the temperature of the high-temperature and high-pressure reaction is 180-220°C
  • the pressure is 0.5-1MPa
  • the stirring reaction is 10-12 hours
  • the temperature-raising rate of the high-temperature reaction is 80-150°C/h.
  • the iron removal is performed by internal circulation through a permanent magnet iron remover until the magnetic material in the slurry is ⁇ 0.2 ppm.
  • the dispersant is selected from PEG800.
  • the method further includes grinding the lithium iron manganese phosphate to a particle size of 100 to 150 nm;
  • the total mass of paraffin wax and dispersant is 2.2% to 2.8% of the mass of lithium iron manganese phosphate, and the mass ratio of paraffin wax to dispersant is 2 to 4:1.
  • the ball mill is carried out in a ball mill.
  • the ball mill is filled with zirconium balls with a diameter of 0.2 ⁇ 0.02mm.
  • the ball mill is a horizontal ball mill, the stirring speed is 80-100r/min, and a jacket is provided on the outer cylinder wall of the ball mill.
  • the calcination process is provided with a heating section, a heat preservation section and a cooling section, and nitrogen is introduced into the calcination process;
  • the calcination process is: raise the temperature to 100 ⁇ 130°C and keep it for 1 ⁇ 3h, raise the temperature to 180 ⁇ 230°C and keep it for 3 ⁇ 6h, then raise the temperature to 300 ⁇ 350°C and keep it for 1 ⁇ 3h, then raise the temperature to 450 ⁇ 500°C and keep it for 1 ⁇ 3h. Then raise the temperature to a temperature of 600-650°C and keep it for 1-3h, then raise the temperature to 700-730°C, keep it for 1-2h, then cool it down to the material temperature ⁇ 80°C before discharging.
  • the present invention provides a method for preparing lithium iron manganese phosphate by a solid phase coating method, which includes the following steps: ball milling lithium iron manganese phosphate, paraffin and dispersant at a temperature above 40°C and mixing them uniformly and then cooling; A mixture is obtained; the mixture is calcined to obtain carbon-coated lithium iron manganese phosphate.
  • the present invention uses paraffin wax as the carbon source, which has low cost, and paraffin wax is a long carbon chain alkane, which can be carbonized to obtain a highly dense carbon coating layer.
  • the present invention adopts a solid-phase coating method to prepare lithium iron manganese phosphate, which can significantly reduce costs, reduce equipment investment, shorten processes, and at the same time, the coating effect is good.
  • Figure 1 is an SEM image of lithium iron manganese phosphate prepared by the present invention
  • Figure 2 is an XRD pattern of lithium iron manganese phosphate prepared by the present invention.
  • the invention provides a method for preparing lithium iron manganese phosphate by a solid phase coating method, which includes the following steps:
  • the mixture is calcined to obtain carbon-coated lithium iron manganese phosphate.
  • the present invention first prepares lithium iron manganese phosphate.
  • the lithium iron manganese phosphate is prepared according to the following method:
  • reaction gas After the iron powder, manganese powder, cerium hydroxide, phosphoric acid and lithium carbonate are mixed and reacted for a period of time, the reaction gas is led out, and then a high-temperature and high-pressure reaction is performed to obtain the reaction product;
  • the reaction product is cooled, iron removed and dried to obtain lithium iron manganese phosphate.
  • iron powder, manganese powder, cerium hydroxide, phosphoric acid and lithium carbonate are added into the high-pressure reaction kettle, and then the gas that reacts for 15 to 30 minutes is discharged.
  • the molar ratio of manganese powder to cerium hydroxide, phosphoric acid and lithium carbonate is 1 ⁇ 2:8 ⁇ 9:0.03 ⁇ 0.06:10 ⁇ 13:5.05 ⁇ 5.1.
  • the molar ratio of iron powder, manganese powder and cerium hydroxide, The molar ratio of phosphoric acid and lithium carbonate is 2:8:0.04:10.8:5.08, 1.5:8.5:0.05:12:5.08, or between 1 ⁇ 2:8 ⁇ 9:0.03 ⁇ 0.06:10 ⁇ 13:5.05 ⁇ 5.1 any value.
  • the purity of the iron powder, manganese powder, and cerium hydroxide is all ⁇ 99.5%, and the manganese powder and iron powder are powders that have passed through a 40-mesh sieve.
  • the high-pressure reaction kettle is heated and pressurized to perform a high-temperature and high-pressure reaction to obtain a reaction product.
  • the temperature of the high-temperature and high-pressure reaction is 180-220°C, preferably 180, 190, 200, 210, 220, or any value between 180-220°C, and the pressure is 0.5-1MPa, preferably 0.6, 0.7, 0.8, 0.9, 1.0, or any value between 0.5 and 1MPa.
  • the temperature rise rate of the high temperature reaction is 80 to 150°C/h. Preferably, it is 80, 90, 100, 110, 120, 130, 140, 150, or any value between 80 and 150°C/h.
  • the reaction product is cooled, iron removed and dried to obtain lithium iron manganese phosphate.
  • the slurry is internally circulated through a permanent magnet iron remover until the magnetic material in the slurry is ⁇ 0.2ppm, then the circulation is stopped; the circulated slurry is filtered, and then the material is dried to obtain ferromanganese phosphate. lithium.
  • the invention uses iron powder and manganese powder as raw materials.
  • hydrogen gas will be generated, and at the same time, the carbonate of lithium carbonate will decompose to obtain carbon dioxide gas.
  • the superposition of the two can greatly increase the pressure in the reaction kettle and create a reducing atmosphere. , can avoid the oxidation of ferrous ions and manganese ions.
  • the present invention does not introduce other impurity anions, so that higher purity lithium iron manganese phosphate can be obtained.
  • the present invention introduces doping ions, that is, cerium ions, whose presence The divalent state and the tetravalent state are reduced to the divalent state in a reducing atmosphere. During the charge and discharge process, they will convert between the divalent state and the tetravalent state, thus increasing the voltage platform.
  • the lithium iron manganese phosphate, paraffin and dispersant are ball milled at above 40°C and mixed evenly and then cooled to obtain a mixture. That is, the outside of the ball mill is a jacket, and hot water is passed into the jacket to achieve a temperature inside the ball mill of above 40°C. ;
  • the dispersant is selected from PEG800.
  • the total mass of paraffin and PEG800 added is 2.2% to 2.8% of the mass of lithium iron manganese phosphate, preferably 2.2%, 2.4%, 2.6%, 2.8%, or any value between 2.2% and 2.8%.
  • the mass ratio of paraffin wax and PEG800 is 2 to 4:1, preferably 2:1, 3:1, 4:1, or any value between 2 and 4:1.
  • the mixture After ball milling and mixing, the mixture is cooled to obtain a mixture.
  • the ball mill is filled with zirconium balls with a diameter of 0.2 ⁇ 0.02mm.
  • the ball mill is a horizontal ball mill for stirring.
  • a jacket is provided on the outer cylinder wall of the ball mill to pass in the medium for heating and cooling.
  • the stirring speed is 80-100 r/min, preferably 80, 90, 100, or any value between 80-100 r/min.
  • the mixture is then calcined, and the calcining process is provided with a heating section, a heat preservation section and a cooling section, and nitrogen is introduced into the calcining process;
  • the calcination process is: raise the temperature to 100 ⁇ 130°C and keep it for 1 ⁇ 3h, raise the temperature to 180 ⁇ 230°C and keep it for 3 ⁇ 6h, then raise the temperature to 300 ⁇ 350°C and keep it for 1 ⁇ 3h, then raise the temperature to 450 ⁇ 500°C and keep it for 1 ⁇ 3h. Then raise the temperature to a temperature of 600-650°C and keep it for 1-3h, then raise the temperature to 700-730°C, keep it for 1-2h, then cool it down to the material temperature ⁇ 80°C before discharging.
  • the calcination process is: 120°C for 1 hour, then 200°C for 3 hours, 325°C for 1 hour, 480°C for 1 hour, then heated to 645°C for 1 hour, and then raised to 720°C. °C, after 2 hours of heat preservation, cool down to the material temperature ⁇ 80 °C before discharging.
  • a rotary kiln is used for calcination.
  • the rotation speed of the rotary kiln is 2 to 4 r/min, preferably 2, 3, 4, or any value between 2 and 4 r/min.
  • An air inlet is provided in the heating section. It is connected to the induced draft fan, and nitrogen is introduced into the rotary kiln at the same time to keep the oxygen content in the rotary kiln below 10ppm.
  • the pressure in the rotary kiln is maintained to be 150 to 300 Pa higher than the external pressure, preferably 150, 200, 250, 300, or Any value between 150 ⁇ 300Pa.
  • the cooling screw conveyor can be used to cool it, and then it can be vacuum packed in the packaging room;
  • the packaging room is a constant temperature and humidity environment, with the temperature below 25°C and humidity ⁇ 10%.
  • the crushing particle size is 1 to 2 ⁇ m.
  • a 100 to 200 mesh screen is used for screening and an electromagnetic iron remover is used to remove iron.
  • the present invention adopts a hydrothermal method to prepare carbon-free lithium iron manganese phosphate.
  • the lithium iron manganese phosphate of the present invention is coated with cerium ions with higher valence and variable valence metal ions, which can improve the quality of the iron manganese phosphate.
  • Lithium's ionic conductivity can also increase voltage.
  • the lithium iron manganese phosphate obtained by the present invention is solid-phase coated, that is, paraffin is added in a ball mill, the paraffin is melted at a temperature higher than the melting point of paraffin, and then wrapped on the surface of the lithium iron manganese phosphate. After cooling, the paraffin solidifies. The paraffin wax adheres to the surface of lithium iron manganese phosphate. Since the zirconium ball is spherical and the surface of lithium iron manganese phosphate is not smooth, during the ball milling process, the paraffin wax adhering to the surface of the zirconium ball can be rubbed away due to the friction of the zirconium ball. , and the present invention can break up the soft agglomerates of lithium iron manganese phosphate prepared hydrothermally during the ball milling process to obtain lithium iron manganese phosphate with smaller particle size.
  • solid-phase coated lithium iron manganese phosphate particles are calcined and carbonized in a rotary kiln to achieve surface carbon coating, and then cooled and discharged, and then after post-processing and packaging, carbon-coated lithium iron manganese phosphate is obtained. .
  • the present invention uses a rotary kiln to achieve carbonization, which can realize the turning movement of the material and achieve uniform carbonization. Compared with the rotary kiln calcination after loading the sagger, the consistency of the material can be higher. According to specific experimental analysis, the material is loaded Put the material into the sagger with a thickness of 10cm, then put it into the roller furnace for calcination, then cool it and take it out. Take samples of the materials on the top, middle and bottom of the sagger. The carbon content of the material in the upper layer is higher than that of the material in the lower layer.
  • the carbon content is 0.3 ⁇ 0.6% higher, and the BET of the upper layer material is 2 ⁇ 5m 2 /g higher than the BET of the lower layer material.
  • the present invention uses a rotary kiln for calcination. Regardless of the upper, middle or lower layers, the consistency of the materials is very high. The difference in carbon content of the materials does not exceed 0.15%, and the difference in BET does not exceed 1.5m 2 /g. Moreover, the rotary kiln has high efficiency, low energy consumption and low equipment investment.
  • the hydrothermal method is used to prepare lithium iron manganese phosphate.
  • the calcination process is equipped with a heating section, a heat preservation section and a cooling section. Nitrogen is introduced into the calcination process.
  • the temperature rise section is: 120°C for 1 hour, then 200°C for 3 hours, 325°C for 1 hour, 480°C for 1 hour, and then raised to a temperature of 645°C. Keep it at °C for 1 hour, then raise the temperature to 720°C. After keeping it for 2 hours, cool it down to the material temperature ⁇ 80°C before discharging.
  • the process of the hydrothermal method is as follows: add iron powder and manganese powder together with cerium hydroxide, phosphoric acid and lithium carbonate into a high-pressure reaction kettle, then lead out the gas that reacted for 20 minutes, and then increase the temperature at a rate of 120°C/h. When the temperature is 210°C and the pressure is 0.6MPa, stir and react for 11 hours, then cool. The slurry is internally circulated through the permanent magnet iron remover. After the magnetic material in the slurry is ⁇ 0.2ppm, the circulation is stopped; the cycled The slurry is filtered, and then the material is dried to obtain lithium iron manganese phosphate.
  • the molar ratio of iron powder, manganese powder to cerium hydroxide, phosphoric acid and lithium carbonate is 2:8:0.04:10.8:5.08;
  • the purity of the iron powder, manganese powder and cerium hydroxide is ⁇ 99.5%, and the manganese powder and iron powder are powders that have passed through a 40-mesh sieve.
  • the ball mill is filled with zirconium balls with a diameter of 0.2 ⁇ 0.02mm.
  • the ball mill is a horizontal ball mill with a stirring speed of 85r/min.
  • a jacket is provided on the outer cylinder wall of the ball mill.
  • a rotary kiln is used for calcination.
  • the rotation speed of the rotary kiln is 3r/min.
  • An air inlet is provided in the heating section. The air inlet is connected to the induced draft fan.
  • nitrogen is introduced into the rotary kiln to maintain the oxygen content in the rotary kiln below 10ppm, while maintaining the pressure in the rotary kiln 180Pa higher than the external pressure.
  • the cooling screw conveyor can be used for cooling, and then it can be vacuum packed in the packaging room;
  • the packaging room is a constant temperature and humidity environment, with the temperature below 25°C and humidity 8%.
  • the crushing particle size is 1.8 ⁇ m
  • a 150 mesh screen is used for screening
  • an electromagnetic iron remover is used to remove iron.
  • the total mass of paraffin and PEG800 added was 2.5% of the mass of lithium iron manganese phosphate.
  • the mass ratio of paraffin wax and PEG800 is 3:1.
  • the product of the invention has high compaction density, excellent capacity, good cycle performance, high high-temperature capacity retention rate, and low cost.
  • the 0.1C charging capacity, 0.1C discharging capacity and first discharge efficiency all adopt the withholding test system.
  • 1C discharge capacity, 1C capacity retention rate after 1,000 cycles at room temperature, and capacity retention rate after being placed at 45°C for 7 days were all measured using soft-pack test lines.
  • the powder resistivity adopts the four-probe method, and the pressure during measurement is 8MPa.
  • PD is measured using an electronic powder compactor, and the measurement pressure is 3T.
  • the measurement method of manganese dissolution is as follows: add 10g of lithium iron manganese phosphate to 90g of 0.1mol/L hydrochloric acid solution, stir and mix at 25°C for 30 minutes, and then filter. Use ICP to measure the manganese element in the filtrate to obtain the manganese dissolution data. .
  • Figure 1 is an SEM image of lithium iron manganese phosphate prepared by the present invention. From the SEM, the particles have a high sphericity and the surface is obviously coated with carbon. And the average primary particle size is about 250 ⁇ 100nm.
  • Figure 2 is an XRD pattern of lithium iron manganese phosphate prepared by the present invention. From the XRD point of view, the crystallinity is high and there are no impurities.
  • the present invention uses a rotary kiln to achieve carbonization and coating. Compared with the roller furnace, it has the following advantages:
  • the equipment investment cost is low.
  • the prices of rotary kilns and roller furnaces with the same production capacity are very different.
  • the equipment price of the rotary kiln is only about 0.2 times that of the roller furnace.
  • the rotary kiln can achieve rotational mixing of materials. Compared with the static sagger loading of the roller furnace, it can avoid the difference between the upper, middle and lower materials in the sagger, and the consistency of the product is greatly improved.
  • the present invention uses a solid phase coating method to achieve coating of the material surface. Compared with liquid phase mixing, the cost can be reduced and the efficiency is high. It avoids the need to use large spray drying equipment for spray drying and avoids the need for spray drying. It consumes a lot of energy to evaporate water. This step alone can reduce the cost per ton by about 1,200 yuan.
  • the process of the present invention is very short, and the present invention uses a ball mill to achieve coating, which can improve the dispersion of materials and avoid agglomeration of materials.
  • the present invention cleverly uses a low-melting point carbon source for coating, and first increases the temperature. , to achieve liquefaction of the carbon source, and then gradually cool it to solidify the carbon source, thereby achieving coating of the carbon source.
  • the present invention uses paraffin wax as the carbon source.
  • the paraffin wax itself has a lubricating effect, reducing the friction of the material and ensuring the mixing of the material and the coating of the carbon source.
  • the present invention uses Ce as a dopant. Cerium ions have divalent and trivalent states, which can improve the ionic conductivity of the product.
  • lithium iron manganese phosphate is prepared, and the lithium iron manganese phosphate is prepared according to the following method:
  • reaction gas After the iron powder, manganese powder, cerium hydroxide, phosphoric acid and lithium carbonate are mixed and reacted for a period of time, the reaction gas is led out, and then a high-temperature and high-pressure reaction is performed to obtain the reaction product;
  • the reaction product is cooled, iron removed and dried to obtain lithium iron manganese phosphate.
  • the molar ratio of iron powder, manganese powder to cerium hydroxide, phosphoric acid and lithium carbonate is 1:9:0.036:10:5.05.
  • the duration of the reaction is 15 minutes;
  • the temperature of the high-temperature and high-pressure reaction is 180°C
  • the pressure is 0.5MPa
  • the stirring reaction is 10 hours
  • the temperature rise rate of the high-temperature reaction is 80°C/h.
  • the iron removal is internal circulation through a permanent magnet iron remover until the magnetic material in the slurry is ⁇ 0.2ppm.
  • the obtained lithium iron manganese phosphate is ground to a particle size of 100 nm; then coating is performed, including the following steps:
  • the mixture is calcined to obtain carbon-coated lithium iron manganese phosphate.
  • the dispersant is selected from PEG800.
  • the total mass of paraffin wax and dispersant is 2.2% of the mass of lithium iron manganese phosphate, and the mass ratio of paraffin wax and dispersant is 2:1.
  • the ball mill is carried out in a ball mill.
  • the ball mill is filled with zirconium balls with a diameter of 0.2 ⁇ 0.02mm.
  • the ball mill is a horizontal ball mill with a stirring speed of 80r/min.
  • the outer cylinder wall of the ball mill is equipped with a jacket.
  • the calcining process is provided with a heating section, a heat preservation section and a cooling section, and nitrogen is introduced into the calcining process;
  • the calcination process is: raise the temperature to 100°C and keep it for 1 hour, raise the temperature to 180°C and keep it for 3 hours, then raise the temperature to 300°C and keep it for 1 hour, then raise the temperature to 450°C and keep it for 1 hour, then raise the temperature to 600°C and keep it for 1 hour, and then raise the temperature to 700°C. After 1 hour of heat preservation, cool down to the material temperature ⁇ 80°C before discharging.
  • lithium iron manganese phosphate is prepared, and the lithium iron manganese phosphate is prepared according to the following method:
  • reaction gas After the iron powder, manganese powder, cerium hydroxide, phosphoric acid and lithium carbonate are mixed and reacted for a period of time, the reaction gas is led out, and then a high-temperature and high-pressure reaction is performed to obtain the reaction product;
  • the reaction product is cooled, iron removed and dried to obtain lithium iron manganese phosphate.
  • the molar ratio of iron powder, manganese powder to cerium hydroxide, phosphoric acid and lithium carbonate is 2:8:0.06:13:5.1.
  • the duration of the reaction is 30 minutes;
  • the temperature of the high-temperature and high-pressure reaction is 220°C
  • the pressure is 1MPa
  • the stirring reaction is 12 hours
  • the temperature rise rate of the high-temperature reaction is 150°C/h.
  • the iron removal is internal circulation through a permanent magnet iron remover until the magnetic material in the slurry is ⁇ 0.2ppm.
  • the mixture is calcined to obtain carbon-coated lithium iron manganese phosphate.
  • the dispersant is selected from PEG800.
  • the total mass of paraffin wax and dispersant is 2.8% of the mass of lithium iron manganese phosphate, and the mass ratio of paraffin wax and dispersant is 4:1.
  • the ball mill is carried out in a ball mill.
  • the ball mill is filled with zirconium balls with a diameter of 0.2 ⁇ 0.02mm.
  • the ball mill is a horizontal ball mill with a stirring speed of 100r/min.
  • a jacket is provided on the outer cylinder wall of the ball mill.
  • the calcining process is provided with a heating section, a heat preservation section and a cooling section, and nitrogen is introduced into the calcining process;
  • the calcination process is: raise the temperature to 130°C and keep it for 3 hours, raise the temperature to 230°C and keep it for 6 hours, then raise the temperature to 350°C and keep it for 3 hours, then raise the temperature to 500°C and keep it for 3 hours, then raise the temperature to 650°C and keep it for 3 hours, and then raise the temperature to 730°C. After 2 hours of heat preservation, cool down to the material temperature ⁇ 80°C before discharging.
  • the conventional process is used to coat the carbon, that is, paraffin and PEG800 are added to water to dissolve, then lithium manganese iron phosphate prepared by hydrothermal method is added to mix, then ground, spray dried, and then calcined in a rotary kiln, as follows:
  • the process of the hydrothermal method is as follows: add iron powder and manganese powder together with cerium hydroxide, phosphoric acid and lithium carbonate into a high-pressure reaction kettle, then lead out the gas that reacted for 20 minutes, and then increase the temperature at a rate of 120°C/h. When the temperature is 210°C and the pressure is 0.6MPa, stir and react for 11 hours, then cool. The slurry is internally circulated through the permanent magnet iron remover. After the magnetic material in the slurry is ⁇ 0.2ppm, the circulation is stopped; the cycled The slurry is filtered, and then the material is dried to obtain lithium iron manganese phosphate.
  • the molar ratio of iron powder, manganese powder to cerium hydroxide, phosphoric acid and lithium carbonate is 2:8:0.04:10.8:5.08;
  • the purity of the iron powder, manganese powder and cerium hydroxide is ⁇ 99.5%, and the manganese powder and iron powder are powders that have passed through a 40-mesh sieve.
  • lithium iron manganese phosphate Use a hydrothermal method to prepare lithium iron manganese phosphate. Add lithium iron manganese phosphate into a ball mill, then add pure water, paraffin and PEG800 with a melting point of 30-40°C, stir and grind until the solid content of the slurry is 35wt%, and grind until the material is The particle size is 120nm, and then spray-dried to obtain the spray-dried material, which is then put into a rotary kiln for calcination;
  • the calcination process is equipped with a heating section, a heat preservation section and a cooling section. Nitrogen is introduced into the calcination process.
  • the temperature rise section is: 120°C for 1 hour, then 200°C for 3 hours, 325°C for 1 hour, 480°C for 1 hour, and then raised to a temperature of 645°C. Keep it at °C for 1 hour, then raise the temperature to 720°C. After keeping it for 2 hours, cool it down to the material temperature ⁇ 80°C before discharging.
  • the ball mill is filled with zirconium balls with a diameter of 0.2 ⁇ 0.02mm.
  • the ball mill is a horizontal ball mill with a stirring speed of 85r/min.
  • a jacket is provided on the outer cylinder wall of the ball mill.
  • a rotary kiln is used for calcination.
  • the rotation speed of the rotary kiln is 3r/min.
  • An air inlet is provided in the heating section. The air inlet is connected to the induced draft fan.
  • nitrogen is introduced into the rotary kiln to maintain the oxygen content in the rotary kiln below 10ppm, while maintaining the pressure in the rotary kiln 180Pa higher than the external pressure.
  • the cooling screw conveyor can be used for cooling, and then it can be vacuum packed in the packaging room;
  • the packaging room is a constant temperature and humidity environment, with the temperature below 25°C and humidity 8%.
  • the crushing particle size is 1.8 ⁇ m
  • a 150 mesh screen is used for screening
  • an electromagnetic iron remover is used to remove iron.
  • the total mass of paraffin and PEG800 added was 2.5% of the mass of lithium iron manganese phosphate.
  • the mass ratio of paraffin wax and PEG800 is 3:1.

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Abstract

本发明提供了一种固相包覆法制备磷酸锰铁锂的方法，包括以下步骤：将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。本发明采用石蜡做为碳源，成本低，且石蜡为长碳链烷烃，可以碳化后得到致密程度高的碳包覆层。本发明采用的为固相包覆法来制备磷酸锰铁锂，可以大幅度降低成本，减少设备投资，缩减工艺，同时包覆效果好。

Description

一种固相包覆法制备磷酸锰铁锂的方法
本申请要求2022年8月1日提交的，申请号为202210915783.0，发明名称为“一种固相包覆法制备磷酸锰铁锂的方法”的中国发明专利申请的优先权，该申请的公开内容以引用的方式并入本文。
技术领域
本发明属于材料技术领域，具体涉及一种固相包覆法制备磷酸锰铁锂的方法。
背景技术
常规的磷酸锰铁锂碳包覆工艺为采用无机碳源直接机械混合或者采用可溶于水的有机物经过干燥后，高温分解碳化来实现碳的包覆。
但是无机碳源包覆存在包覆不均匀的现象，有机碳源的包覆，需要进行喷雾干燥等过程，需要消耗大量的能耗，根据实际情况，每吨磷酸锰铁锂在喷雾干燥，所需的费用在1000～1200元，如果按照年产1万吨的磷酸锰铁锂，则仅仅这一步，产生的费用为1000万～1200万。同时大型的喷雾干燥设备价格也比较高，年产1万吨的磷酸锰铁锂所需要的喷雾干燥的设备价值就达到了1000万以上。
发明内容
有鉴于此，本发明要解决的技术问题在于提供一种固相包覆法制备磷酸锰铁锂的方法，本发明采用的为固相包覆法来制备磷酸锰铁锂，可以大幅度降低成本，减少设备投资，缩减工艺，同时包覆效果好。
本发明提供了一种固相包覆法制备磷酸锰铁锂的方法，包括以下步骤：
将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；
将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。
优选的，所述磷酸锰铁锂按照如下方法进行制备：
将铁粉、锰粉、氢氧化铈、磷酸和碳酸锂混合进行反应一段时间后，将反应气体导出，然后进行高温高压反应，得到反应产物；
将所述反应产物冷却、除铁以及干燥，得到磷酸锰铁锂。
优选的，所述铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为1～2:8～9:0.03～0.06:10～13:5.05～5.1。
优选的，所述反应一段时间的时长为15～30min；
所述高温高压反应的温度为180～220℃，压力为0.5～1MPa，搅拌反应10～12h，所述高温反应的升温速度为80～150℃/h。
优选的，所述除铁为通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm。
优选的，所述分散剂选自PEG800。
优选的，磷酸锰铁锂、石蜡和分散剂在混合之前，还包括将磷酸锰铁锂研磨至粒径为100～150nm；
优选的，石蜡和分散剂的总质量为磷酸锰铁锂的质量的2.2％～2.8％，石蜡和分散剂的质量比为2～4:1。
优选的，球磨在球磨机内进行，球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，搅拌速度为80-100r/min,球磨机外筒壁上设置有夹套。
优选的，所述煅烧的过程设置有升温段、保温段和降温段，煅烧过程通入氮气；
煅烧过程为：升温至100～130℃保温1～3h，升温至180～230℃保温3～6h，再升温至300～350℃保温1～3h，接着升温至450～500℃保温1～3h，然后升温至温度为600～650℃保温1～3h，然后升温至700～730℃，保温1～2h后，降温至物料温度≤80℃后出料。
与现有技术相比，本发明提供了一种固相包覆法制备磷酸锰铁锂的方法，包括以下步骤：将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。本发明采用石蜡做为碳源，成本低，且石蜡为长碳链烷烃，可以碳化后得到致密程度高的碳包覆层。本发明采用的为固相包覆法来制备磷酸锰铁锂，可以大幅度降低成本，减少设备投资，缩减工艺，同时包覆效果好。
附图说明
图1为本发明制备的磷酸铁锰锂的SEM图；
图2为本发明制备的磷酸铁锰锂的XRD图。
具体实施方式
本发明提供了一种固相包覆法制备磷酸锰铁锂的方法，包括以下步骤：
将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；
将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。
本发明首先制备磷酸锰铁锂，在本发明中，所述磷酸锰铁锂按照如下方法进行制备：
将铁粉、锰粉、氢氧化铈、磷酸和碳酸锂混合进行反应一段时间后，将反应气体导出，然后进行高温高压反应，得到反应产物；
将所述反应产物冷却、除铁以及干燥，得到磷酸锰铁锂。
具体的，将铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂加入到高压反应釜内，然后将反应15～30min的气体导出后。其中，锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为1～2:8～9:0.03～0.06:10～13:5.05～5.1，优选的，铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为2:8:0.04:10.8:5.08、1.5:8.5:0.05:12:5.08，或1～2:8～9:0.03～0.06:10～13:5.05～5.1之间的任意值。所述铁粉、锰粉、氢氧化铈的纯度均≥99.5％，所述锰粉、铁粉均为过40目筛的粉末。
接着，将高压反应釜升温加压，进行高温高压反应，得到反应产物。
其中，所述高温高压反应的温度为180～220℃，优选为180、190、200、210、220，或180～220℃之间的任意值，压力为0.5～1MPa，优选为0.6、0.7、0.8、0.9、1.0，或0.5～1MPa之间的任意值，搅拌反应10～12h，优选为10、11、12，或10～12h，所述高温反应的升温速度为80～150℃/h，优选为80、90、100、110、120、130、140、150，或80～150℃/h之间的任意值。
将所述反应产物冷却、除铁以及干燥，得到磷酸锰铁锂。后冷却，将浆料通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm后，停止循环；将循环后的浆料过滤，然后将物料经过干燥后，得到磷酸锰铁锂。
本发明采用铁粉和锰粉为原材料，在反应过程中，会产生得到氢气，同时碳酸锂的碳酸根分解得到二氧化碳气体，两者叠加，可以大大提高反应釜内的压力，同时还原性的气氛，可以避免亚铁离子和锰离子的氧化，同时，本发明不会引入其他杂质阴离子，从而可以得到纯度更高的磷酸锰铁锂，同时本发明引入了掺杂离子，即铈离子，其存在二价态和四价态，在还原氛围 状态下，被还原为二价态，在充放电过程中，会在二价态和四价态之间转换，从而提升电压平台。
得到磷酸锰铁锂后，将磷酸锰铁锂研磨至粒径为100～150nm。
接着，将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物，即球磨机外部为夹套，夹套内通入热水，来实现球磨机内的温度为40℃以上；
在本发明中，所述分散剂选自PEG800。加入的石蜡和PEG800的总质量为磷酸锰铁锂的质量的2.2％～2.8％，优选为2.2％、2.4％、2.6％、2.8％，或2.2％～2.8％之间的任意值。石蜡和PEG800的质量比为2～4:1，优选为2:1、3:1、4:1，或2～4:1之间的任意值。
球磨混合后，进行冷却，得到混合物。
其中，球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，进行搅拌，球磨机外筒壁上设置有夹套，用于通入用于加热和冷却的介质。所述搅拌的速度为80～100r/min，优选为80、90、100，或80～100r/min之间的任意值。
然后将所述混合物进行煅烧，所述煅烧的过程设置有升温段、保温段和降温段，煅烧过程通入氮气；
煅烧过程为：升温至100～130℃保温1～3h，升温至180～230℃保温3～6h，再升温至300～350℃保温1～3h，接着升温至450～500℃保温1～3h，然后升温至温度为600～650℃保温1～3h，然后升温至700～730℃，保温1～2h后，降温至物料温度≤80℃后出料。
在本发明的一些具体实施方式中，煅烧的过程为：120℃保温1h，然后200℃保温3h，325℃保温1h，480℃保温1h，然后升温至温度为645℃保温1h，然后升温至720℃，保温2h后，降温至物料温度≤80℃后出料。
在煅烧过程，采用回转窑煅烧，回转窑的转速为2～4r/min，优选为2、3、4，或2～4r/min之间的任意值，在升温段设置有引风口，引风口与引风机连通，同时回转窑内通入氮气，维持回转窑内的氧气含量低于10ppm，同时维持回转窑内的压力比外界压力高150～300Pa，优选为150、200、250、300，或150～300Pa之间的任意值。
回转窑出料温度若高于80℃，则可以采用冷却螺旋输送机进行冷却，然 后到包装间进行真空包装；
包装间为恒温恒湿环境，温度低于25℃，湿度≤10％。
在进行真空包装前，需要进行粉碎、筛分和除铁，粉碎粒径为1～2μm，筛分采用100～200目筛网，除铁采用电磁除铁器。
本发明采用水热法来制备得到无碳包覆的磷酸锰铁锂，同时本发明的磷酸锰铁锂中包覆了价态较高且为变价金属离子的铈离子，即可以提高磷酸锰铁锂的离子电导性，同时也可以提升电压。
本发明得到的磷酸锰铁锂经过固相包覆，即在球磨机内，加入石蜡，在高于石蜡熔点的温度下石蜡融化，然后包裹在磷酸锰铁锂的表面，然后冷却后，石蜡固化，使得石蜡粘附在磷酸锰铁锂表面，由于锆球为球形，而磷酸锰铁锂表面为不光滑，在球磨过程，由于锆球的摩擦，而可以将粘附在锆球表面的石蜡摩擦掉，且本发明在球磨过程，可以将水热制备的磷酸锰铁锂的软团聚打散，得到粒径较小的磷酸锰铁锂。
本发明将固相包覆的磷酸锰铁锂颗粒在回转窑内煅烧，碳化，实现表面碳包覆，然后冷却后出料，然后经过后处理和包装后，得到碳包覆的磷酸锰铁锂。
本发明采用回转窑来实现碳化，可以实现物料的翻转运动，可以实现碳化的均匀，相比较匣钵装料后回转窑煅烧，可以使得物料的一致性更高，根据具体实验分析，将物料装入到匣钵内，装料厚度为10cm，然后放入到辊道炉内的煅烧后，然后冷却后取出，将匣钵上中下的物料取样检测，则上层的物料碳含量比下层的物料的碳含量高0.3～0.6％，而上层的物料BET比下层的物料的BET高2～5m 2/g。而本发明采用回转窑煅烧，无论上层、中层和下层，物料的一致性非常高，物料的碳含量相差不超过0.15％，BET的相差不超过1.5m 2/g。且回转窑的效率高、能耗低且设备投资少。
为了进一步理解本发明，下面结合实施例对本发明提供的固相包覆法制备磷酸锰铁锂的方法进行说明，本发明的保护范围不受以下实施例的限制。
实施例1
采用水热法来制备磷酸锰铁锂，将磷酸锰铁锂加入球磨机内，搅拌研磨，研磨至物料粒径为120nm，此时在球磨机的夹套内加入温度为45℃的热水进行循环，维持球磨机内的温度在40℃以上，然后加入熔点为30-40℃的石蜡和 PEG800，继续进行搅拌，搅拌45min后，然后通入冷却水进行冷却，冷却至温度为20℃，然后将物料取出，然后进行煅烧；
煅烧过程设置有升温段、保温段和降温段，煅烧过程通入氮气，升温段为，120℃保温1h，然后200℃保温3h，325℃保温1h，480℃保温1h，然后升温至温度为645℃保温1h，然后升温至720℃，保温2h后，降温至物料温度≤80℃后出料。
所述水热法的工艺为：将铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂一起加入到高压反应釜内，然后将反应20min的气体导出后，升温速度为120℃/h，升温至温度为210℃，压力为0.6MPa，搅拌反应11h，然后冷却，将浆料通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm后，停止循环；将循环后的浆料过滤，然后将物料经过干燥后，得到磷酸锰铁锂。
铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为2：8:0.04:10.8:5.08；
所述铁粉、锰粉、氢氧化铈的纯度均≥99.5％，所述锰粉、铁粉均为过40目筛的粉。
球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，搅拌速度为85r/min，球磨机外筒壁上设置有夹套。
在煅烧过程，采用回转窑煅烧，回转窑的转速为3r/min，在升温段设置有引风口，引风口与引风机连通，同时回转窑内通入氮气，维持回转窑内的氧气含量低于10ppm，同时维持回转窑内的压力比外界压力高180Pa。
回转窑出料温度若高于80℃，则可以采用冷却螺旋输送机进行冷却，然后到包装间进行真空包装；
包装间为恒温恒湿环境，温度低于25℃，湿度8％。
在进行真空包装前，需要进行粉碎、筛分和除铁，粉碎粒径为1.8μm，筛分采用150目筛网，除铁采用电磁除铁器。
加入的石蜡和PEG800的总质量为磷酸锰铁锂的质量的2.5％。石蜡和PEG800的质量比为3:1。
最终得到的产品的结果如下：
表1
Figure PCTCN2022141941-appb-000001
Figure PCTCN2022141941-appb-000002
本发明的产品压实密度高，容量优异，且循环性能好，高温容量保持率高，且成本低。
本实施例的0.1C充电容量、0.1C放电容量和首次放电效率均采用扣电测试系统。1C放电容量、1C常温循环1000周后的容量保持率、45℃放置7天容量保持率均采用软包测试线内测量。软包的容量为0.3Ah，其中正极材料的配方为材料:SP:CNT:PVDF＝80:1:12:7。
粉末电阻率采用四探针法，测量时的压力为8MPa。
PD采用电子粉末压实仪测量，测量压力为3T。
锰溶出的测量方法为：将10g的磷酸锰铁锂加入90g0.1mol/L的盐酸溶液中，在25℃搅拌混合30min，然后过滤，得到的滤液采用ICP测量其中的锰元素，得到锰溶出数据。
参见图1，图1为本发明制备的磷酸铁锰锂的SEM图。从SEM来看，颗粒球形度较高，表面明显包覆有碳。且平均一次粒径大约在250±100nm左右。
参见图2，图2为本发明制备的磷酸铁锰锂的XRD图。从XRD来看，结晶度高，无杂相。
本发明在碳包覆阶段，采用回转窑来实现碳化和包覆，相比较辊道炉具有以下优势：
1.设备投资成本低，相同产能的回转窑和辊道炉，价格相差很大，回转窑的设备价格仅为辊道炉的0.2倍左右。
2.同时，回转窑可以实现物料的转动混合，相比较静态的辊道炉的匣钵装 料，可以避免匣钵上中下物料的差异，产品的一致性大大提高。
3.本发明采用固相包覆法来实现物料表面的包覆，相比较液相的混合，可以降低成本，且效率高，避免了需要采用大型喷雾干燥设备来进行喷雾干燥，且避免了需要消耗大量的能耗来蒸发水分，仅仅这一步骤，可以降低吨成本1200元左右。
4.本发明的流程很短，且本发明采用球磨机内实现包覆，可以提高物料的分散性，避免物料的团聚，且本发明巧妙的利用了低熔点的碳源进行包覆，先提高温度，实现碳源的液化，然后再逐步冷却，将碳源固化，从而实现碳源的包覆。且本发明采用了石蜡为碳源，石蜡本身具有润滑作用，降低物料的摩擦力，保证了物料的混合和碳源的包覆。
5.本发明采用Ce作用掺杂剂，铈离子有二价态和三价态，可以提高产品的离子导电性。
实施例2
首先制备磷酸锰铁锂，所述磷酸锰铁锂按照如下方法进行制备：
将铁粉、锰粉、氢氧化铈、磷酸和碳酸锂混合进行反应一段时间后，将反应气体导出，然后进行高温高压反应，得到反应产物；
将所述反应产物冷却、除铁以及干燥，得到磷酸锰铁锂。
其中，所述铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为1:9:0.036:10:5.05。
所述反应一段时间的时长为15min；
所述高温高压反应的温度为180℃，压力为0.5MPa，搅拌反应10h，所述高温反应的升温速度为80℃/h。
所述除铁为通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm。
将得到的磷酸锰铁锂研磨至粒径为100nm；然后进行包覆，包括以下步骤：
将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；
将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。
其中，所述分散剂选自PEG800。石蜡和分散剂的总质量为磷酸锰铁锂的 质量的2.2％，石蜡和分散剂的质量比为2:1。
球磨在球磨机内进行，球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，搅拌速度为80r/min,球磨机外筒壁上设置有夹套。
所述煅烧的过程设置有升温段、保温段和降温段，煅烧过程通入氮气；
煅烧过程为：升温至100℃保温1h，升温至180℃保温3h，再升温至300℃保温1h，接着升温至450℃保温1h，然后升温至温度为600℃保温1h，然后升温至700℃，保温1h后，降温至物料温度≤80℃后出料。
最终得到的产品的结果如下：
表2
Figure PCTCN2022141941-appb-000003
实施例3
首先制备磷酸锰铁锂，所述磷酸锰铁锂按照如下方法进行制备：
将铁粉、锰粉、氢氧化铈、磷酸和碳酸锂混合进行反应一段时间后，将反应气体导出，然后进行高温高压反应，得到反应产物；
将所述反应产物冷却、除铁以及干燥，得到磷酸锰铁锂。
其中，所述铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为2:8:0.06:13:5.1。
所述反应一段时间的时长为30min；
所述高温高压反应的温度为220℃，压力为1MPa，搅拌反应12h，所述高温反应的升温速度为150℃/h。
所述除铁为通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm。
将磷酸锰铁锂研磨至粒径为150nm；然后进行包覆，包括以下步骤：
将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；
将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。
其中，所述分散剂选自PEG800。石蜡和分散剂的总质量为磷酸锰铁锂的质量的2.8％，石蜡和分散剂的质量比为4:1。
球磨在球磨机内进行，球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，搅拌速度为100r/min,球磨机外筒壁上设置有夹套。
所述煅烧的过程设置有升温段、保温段和降温段，煅烧过程通入氮气；
煅烧过程为：升温至130℃保温3h，升温至230℃保温6h，再升温至350℃保温3h，接着升温至500℃保温3h，然后升温至温度为650℃保温3h，然后升温至730℃，保温2h后，降温至物料温度≤80℃后出料。
最终得到的产品的结果如下：
表3
Figure PCTCN2022141941-appb-000004
对比例
采用常规的工艺来包覆碳，即采用石蜡和PEG800加入水溶解，然后加入水热法制备的磷酸锰铁锂混合，然后研磨后，喷雾干燥，然后回转窑内煅烧，具体如下：
所述水热法的工艺为：将铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂一起加入到高压反应釜内，然后将反应20min的气体导出后，升温速度为120℃/h，升温至温度为210℃，压力为0.6MPa，搅拌反应11h，然后冷却，将浆料通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm后，停止循环；将循环后的浆料过滤，然后将物料经过干燥后，得到磷酸锰铁锂。
铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为2：8:0.04:10.8:5.08；
所述铁粉、锰粉、氢氧化铈的纯度均≥99.5％，所述锰粉、铁粉均为过40目筛的粉。
采用水热法来制备磷酸锰铁锂，将磷酸锰铁锂加入球磨机内，然后加入纯水和熔点为30-40℃的石蜡、PEG800，搅拌研磨，浆料固含量为35wt％，研磨至物料粒径为120nm，然后喷雾干燥，得到喷雾干燥料，然后放入回转窑内煅烧；
煅烧过程设置有升温段、保温段和降温段，煅烧过程通入氮气，升温段为，120℃保温1h，然后200℃保温3h，325℃保温1h，480℃保温1h，然后升温至温度为645℃保温1h，然后升温至720℃，保温2h后，降温至物料温度≤80℃后出料。
球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，搅拌速度为85r/min，球磨机外筒壁上设置有夹套。
在煅烧过程，采用回转窑煅烧，回转窑的转速为3r/min，在升温段设置有引风口，引风口与引风机连通，同时回转窑内通入氮气，维持回转窑内的氧气含量低于10ppm，同时维持回转窑内的压力比外界压力高180Pa。
回转窑出料温度若高于80℃，则可以采用冷却螺旋输送机进行冷却，然后到包装间进行真空包装；
包装间为恒温恒湿环境，温度低于25℃，湿度8％。
在进行真空包装前，需要进行粉碎、筛分和除铁，粉碎粒径为1.8μm，筛分采用150目筛网，除铁采用电磁除铁器。
加入的石蜡和PEG800的总质量为磷酸锰铁锂的质量的2.5％。石蜡和PEG800的质量比为3:1。
最终得到的产品的结果如下：
表4
Figure PCTCN2022141941-appb-000005
Figure PCTCN2022141941-appb-000006
以上所述仅是本发明的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也应视为本发明的保护范围。

Claims (10)

  1. 一种固相包覆法制备磷酸锰铁锂的方法，其特征在于，包括以下步骤：
    将磷酸锰铁锂、石蜡和分散剂在40℃以上球磨混合均匀后冷却，得到混合物；
    将所述混合物煅烧，得到碳包覆的磷酸锰铁锂。
  2. 根据权利要求1所述的方法，其特征在于，所述磷酸锰铁锂按照如下方法进行制备：
    将铁粉、锰粉、氢氧化铈、磷酸和碳酸锂混合进行反应一段时间后，将反应气体导出，然后进行高温高压反应，得到反应产物；
    将所述反应产物冷却、除铁以及干燥，得到磷酸锰铁锂。
  3. 根据权利要求2所述的方法，其特征在于，所述铁粉、锰粉与氢氧化铈、磷酸以及碳酸锂的摩尔比为1～2:8～9:0.03～0.06:10～13:5.05～5.1。
  4. 根据权利要求2所述的方法，其特征在于，所述反应一段时间的时长为15～30min；
    所述高温高压反应的温度为180～220℃，压力为0.5～1MPa，搅拌反应10～12h，所述高温反应的升温速度为80～150℃/h。
  5. 根据权利要求2所述的方法，其特征在于，所述除铁为通过永磁除铁器进行内循环，循环至浆料中的磁性物质≤0.2ppm。
  6. 根据权利要求1所述的方法，其特征在于，所述分散剂选自PEG800。
  7. 根据权利要求1所述的方法，其特征在于，磷酸锰铁锂、石蜡和分散剂在混合之前，还包括将磷酸锰铁锂研磨至粒径为100～150nm；
  8. 根据权利要求1所述的方法，其特征在于，石蜡和分散剂的总质量为磷酸锰铁锂的质量的2.2％～2.8％，石蜡和分散剂的质量比为2～4:1。
  9. 根据权利要求1所述的方法，其特征在于，球磨在球磨机内进行，球磨机内，填装有直径为0.2±0.02mm的锆球，球磨机为卧式球磨机，搅拌速度为80-100r/min,球磨机外筒壁上设置有夹套。
  10. 根据权利要求1所述的方法，其特征在于，所述煅烧的过程设置有升温段、保温段和降温段，煅烧过程通入氮气；
    煅烧过程为：升温至100～130℃保温1～3h，升温至180～230℃保温3～6h，再升温至300～350℃保温1～3h，接着升温至450～500℃保温1～3h，然后升温 至温度为600～650℃保温1～3h，然后升温至700～730℃，保温1～2h后，降温至物料温度≤80℃后出料。
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