Lithium manganese iron phosphate, preparation method and application thereof

Abstract

This invention relates to lithium manganese iron phosphate, its preparation method, and its application, belonging to the field of electrode material technology. The preparation method includes the following steps: W1. Preparing manganese iron oxide nanoparticles; W2. Carbon coating the manganese iron oxide nanoparticles; W3. Sintering the carbon-coated manganese iron oxide nanoparticles to obtain lithium manganese iron phosphate. The precursor solution provided by this invention contains acrylic acid and lithium acrylate, which work together through electrostatic repulsion and steric hindrance to disperse manganese and ferrous ions, achieving better dispersion. The preparation method of lithium manganese iron phosphate innovatively uses stepwise ball milling in the carbon coating stage. By sequentially adding lithium dodecyl sulfate and EDTA during ball milling, the carbon coating layer thickness becomes more uniform, and the carbon source adheres better to the surface of inorganic compounds such as lithium, iron, and manganese sources during ball milling, resulting in better dispersion and coating of raw materials.

Description

Technical Field

[0001] The present invention belongs to the technical field of electrode materials, and relates to lithium iron manganese phosphate and a preparation method and application thereof. Background Art

[0002] Existing lithium iron manganese phosphate LiFe 1-x Mn x PO4(0 < x < 1) materials usually use common carbon sources for preparing lithium iron phosphate, such as acetylene black, citric acid, sucrose, glucose, polyvinyl alcohol, and polyethylene glycol, etc., as carbon source coating agents; after these organic substances are sintered and carbonized at high temperature, the conductivity and cycle performance of the materials can be effectively improved, but the thickness and coating effect of these carbon layers are often not effectively controlled; this is mainly because the carbon source cannot adhere to the surfaces of inorganic compounds such as lithium source, iron source, and manganese source during the slurry sanding process, and thus cannot play the role of dispersing and coating raw materials.

[0003] Invention CN116835560A discloses a lithium iron manganese phosphate composite material, a preparation method thereof, and a positive electrode sheet. The preparation method includes: Step S1, mixing a chelating agent, an iron source, a manganese source, a phosphorus source, and water to form a raw material system, volatilizing the raw material system to form a gel, and performing a first sintering on the gel to obtain a lithium iron manganese phosphate precursor; Step S2, mixing the lithium iron manganese phosphate precursor, a lithium source, a carbon source, and an organic phosphate, performing sanding and drying to obtain a lithium iron manganese phosphate precursor; Step S3, performing a second sintering on the lithium iron manganese phosphate precursor to obtain a lithium iron manganese phosphate composite material.

[0004] Invention CN117049516A discloses a method for preparing a novel carbon-coated material and coating a lithium iron manganese phosphate positive electrode material. A novel carbon-coated material uses organic polyacids such as citric acid to perform esterification condensation reaction with dihydric alcohols, and by controlling the content of terminal carboxyl groups and the molecular weight of this polymer, it is both a carbon source for lithium iron manganese phosphate and a good dispersant. A method for coating a lithium iron manganese phosphate positive electrode material, selecting citric acid polyethylene glycol esters as the carbon source and dispersant for lithium iron manganese phosphate, reducing the particle size of the slurry during the sanding process, obtaining a spray material with more regular morphology, sintering in a roller hearth furnace and pulverizing with an air flow pulverizer, to obtain a high-capacity lithium iron manganese phosphate material with good sphericity, uniform carbon source distribution, and smaller particle size of the material. Summary of the Invention

[0005] The purpose of the present invention is to provide a lithium iron manganese phosphate and a preparation method and application thereof, which have the characteristics of a thin and uniform carbon coating layer.

[0006] The purpose of the present invention can be achieved by the following technical solutions:

[0007] A preparation method of lithium iron manganese phosphate includes the following steps:

[0008] W1. Preparation of manganese iron oxide nanoparticles;

[0009] W2. Carbon coating of manganese iron oxide nanoparticles;

[0010] W3. Sinter the carbon-coated manganese iron oxide nanoparticles to obtain lithium manganese iron phosphate.

[0011] As a preferred embodiment of the present invention, the preparation of the manganese iron oxide nanoparticles in step W1 includes the following steps:

[0012] X1. Dissolve the manganese source and iron source in a solvent to obtain a precursor solution;

[0013] X2. Filter the precursor solution, adjust the pH value, and preheat it to obtain a pretreated precursor solution;

[0014] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 10-50 L / h and transported to a reactor for calcination at 600-900℃ to obtain manganese iron oxide nanoparticles.

[0015] As a preferred embodiment of the present invention, the precursor solution in step X1 is composed of the following components by weight: 5-9 parts MnCl2, 3-6 parts FeCl2, 22-26 parts deionized water, 1-2 parts acrylic acid and 0.5-1 parts lithium acrylate.

[0016] As a preferred embodiment of the present invention, the carbon coating in step W2 includes the following steps:

[0017] Y1. Manganese iron oxide nanoparticles were mixed with lithium dihydrogen phosphate, phosphoric acid, glucose, lithium dodecyl sulfate and deionized water in a ball mill and ball milled once to obtain a carbon-coated mixture;

[0018] Y2. The carbon-coated mixture was mixed with glucose, EDTA and deionized water in a ball mill and then ball-milled a second time to obtain carbon-coated manganese iron oxide nanoparticles.

[0019] As a preferred technical solution of the present invention, the sintering in step W3 refers to sintering carbon-coated manganese iron oxide nanoparticles at a temperature of 700-800°C for 8-12 hours to obtain lithium manganese iron phosphate.

[0020] As a preferred embodiment of the present invention, the pH value in step X2 is 2.5 to 3.5, the preheating temperature is 70 to 80°C, and the preheating is continued for 10 to 15 minutes.

[0021] As a preferred technical solution of the present invention, the components in step Y1 are: 30-50 parts of manganese iron oxide nanoparticles, 20-30 parts of lithium dihydrogen phosphate, 10-20 parts of phosphoric acid, 15-25 parts of glucose, 5-10 parts of lithium dodecyl sulfate, and 5-9 parts of deionized water.

[0022] As a preferred technical solution of the present invention, the carbon-coated mixture in step Y2 comprises 30-50 parts by weight, glucose 10-15 parts by weight, EDTA 5-10 parts by weight, and deionized water 3-5 parts by weight.

[0023] A lithium manganese iron phosphate prepared according to the above preparation method.

[0024] In a preferred embodiment of the present invention, the lithium manganese iron phosphate is used as an electrode material.

[0025] The beneficial effects of this invention are:

[0026] (1) The precursor solution of the preparation formula of lithium manganese iron phosphate provided by the present invention contains acrylic acid and lithium acrylate. The two act together on manganese ions and ferrous ions through electrostatic repulsion and steric hindrance, so as to achieve better dispersion effect.

[0027] (2) The method for preparing lithium manganese iron phosphate provided by the present invention innovatively uses stepwise ball milling in the carbon coating process of manganese iron oxide nanoparticles. By sequentially adding lithium dodecyl sulfate and EDTA for ball milling, the carbon coating layer thickness is more uniform, and the carbon source is better attached to the surface of inorganic compounds such as lithium source, iron source and manganese source during the ball milling process, thereby achieving better dispersion and coating of raw materials. Detailed Implementation

[0028] To further illustrate the technical means and effects of the present invention in achieving its intended purpose, the following detailed description of the specific implementation methods, structures, features, and effects of the present invention, in conjunction with embodiments, is provided below.

[0029] Example 1

[0030] A method for preparing lithium manganese iron phosphate includes the following steps:

[0031] W1. Preparation of manganese iron oxide nanoparticles;

[0032] W2. Carbon coating of manganese iron oxide nanoparticles;

[0033] W3. Carbon-coated manganese iron oxide nanoparticles were sintered at 700℃ for 8 hours to obtain lithium manganese iron phosphate.

[0034] The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps:

[0035] X1. Mix 5 parts by weight of MnCl2, 3 parts by weight of FeCl2, 22 parts by weight of deionized water, 1 part by weight of acrylic acid and 0.5 parts by weight of lithium acrylate until dissolved to obtain a precursor solution;

[0036] X2. Filter the precursor solution, adjust the pH to 2.5, and preheat it at 70℃ for 10 minutes to obtain the pretreated precursor solution.

[0037] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 35 L / h and transported to a reactor for calcination at 700 °C to obtain manganese iron oxide nanoparticles.

[0038] The carbon coating described in step W2 includes the following steps:

[0039] Y1. Mix 30 parts by weight of manganese iron oxide nanoparticles with 20 parts by weight of lithium dihydrogen phosphate, 10 parts by weight of phosphoric acid, 15 parts by weight of glucose, 5 parts by weight of lithium dodecyl sulfate and 5 parts by weight of deionized water in a ball mill and perform ball milling once to obtain a carbon-coated mixture.

[0040] Y2. Mix 30 parts by weight of carbon-coated mixture with 10 parts by weight of glucose, 5 parts by weight of EDTA and 3 parts by weight of deionized water in a ball mill and perform secondary ball milling to obtain carbon-coated manganese iron oxide nanoparticles.

[0041] Example 2

[0042] A method for preparing lithium manganese iron phosphate includes the following steps:

[0043] W1. Preparation of manganese iron oxide nanoparticles;

[0044] W2. Carbon coating of manganese iron oxide nanoparticles;

[0045] W3. Carbon-coated manganese iron oxide nanoparticles are sintered at 750℃ for 10 hours to obtain lithium manganese iron phosphate.

[0046] The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps:

[0047] X1. Mix 7 parts by weight of MnCl2, 5 parts by weight of FeCl2, 24 parts by weight of deionized water, 1.5 parts by weight of acrylic acid and 0.7 parts by weight of lithium acrylate until dissolved to obtain a precursor solution;

[0048] X2. Filter the precursor solution, adjust the pH to 3.0, and preheat it at 75℃ for 12 minutes to obtain the pretreated precursor solution.

[0049] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 40 L / h and transported to a reactor for calcination at 750 °C to obtain manganese iron oxide nanoparticles.

[0050] The carbon coating described in step W2 includes the following steps:

[0051] Y1. Mix 40 parts by weight of manganese iron oxide nanoparticles with 26 parts by weight of lithium dihydrogen phosphate, 15 parts by weight of phosphoric acid, 20 parts by weight of glucose, 7 parts by weight of lithium dodecyl sulfate and 7 parts by weight of deionized water in a ball mill and perform ball milling once to obtain a carbon-coated mixture.

[0052] Y2. 40 parts by weight of carbon-coated mixture were mixed with 13 parts by weight of glucose, 7 parts by weight of EDTA and 4 parts by weight of deionized water in a ball mill and then ball-milled twice to obtain carbon-coated manganese iron oxide nanoparticles.

[0053] Example 3

[0054] A method for preparing lithium manganese iron phosphate includes the following steps:

[0055] W1. Preparation of manganese iron oxide nanoparticles;

[0056] W2. Carbon coating of manganese iron oxide nanoparticles;

[0057] W3. Carbon-coated manganese iron oxide nanoparticles are sintered at 800℃ for 12 hours to obtain lithium manganese iron phosphate.

[0058] The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps:

[0059] X1. Mix 9 parts by weight of MnCl2, 6 parts by weight of FeCl2, 26 parts by weight of deionized water, 2 parts by weight of acrylic acid and 1 part by weight of lithium acrylate until dissolved to obtain a precursor solution;

[0060] X2. Filter the precursor solution, adjust the pH to 3.5, and preheat it at 80℃ for 15 minutes to obtain the pretreated precursor solution.

[0061] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 45 L / h and transported to a reactor for calcination at 800 °C to obtain manganese iron oxide nanoparticles.

[0062] The carbon coating described in step W2 includes the following steps:

[0063] Y1. Mix 50 parts by weight of manganese iron oxide nanoparticles with 30 parts by weight of lithium dihydrogen phosphate, 20 parts by weight of phosphoric acid, 25 parts by weight of glucose, 10 parts by weight of lithium dodecyl sulfate and 9 parts by weight of deionized water in a ball mill and perform ball milling once to obtain a carbon-coated mixture.

[0064] Y2. Mix 50 parts by weight of carbon-coated mixture with 15 parts by weight of glucose, 10 parts by weight of EDTA and 5 parts by weight of deionized water in a ball mill and perform secondary ball milling to obtain carbon-coated manganese iron oxide nanoparticles.

[0065] Comparative Example 1

[0066] A method for preparing lithium manganese iron phosphate includes the following steps:

[0067] W1. Preparation of manganese iron oxide nanoparticles;

[0068] W2. Carbon coating of manganese iron oxide nanoparticles;

[0069] W3. Carbon-coated manganese iron oxide nanoparticles are sintered at 800℃ for 12 hours to obtain lithium manganese iron phosphate.

[0070] The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps:

[0071] X1. Mix 9 parts by weight of MnCl2, 6 parts by weight of FeCl2 and 26 parts by weight of deionized water until dissolved to obtain a precursor solution;

[0072] X2. Filter the precursor solution, adjust the pH to 3.5, and preheat it at 80℃ for 15 minutes to obtain the pretreated precursor solution.

[0073] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 45 L / h and transported to a reactor for calcination at 800 °C to obtain manganese iron oxide nanoparticles.

[0074] The carbon coating described in step W2 includes the following steps:

[0075] Y1. Mix 50 parts by weight of manganese iron oxide nanoparticles with 30 parts by weight of lithium dihydrogen phosphate, 20 parts by weight of phosphoric acid, 25 parts by weight of glucose, 10 parts by weight of lithium dodecyl sulfate and 9 parts by weight of deionized water in a ball mill and perform ball milling once to obtain a carbon-coated mixture.

[0076] Y2. Mix 50 parts by weight of carbon-coated mixture with 15 parts by weight of glucose, 10 parts by weight of EDTA and 5 parts by weight of deionized water in a ball mill and perform secondary ball milling to obtain carbon-coated manganese iron oxide nanoparticles.

[0077] Comparative Example 2

[0078] A method for preparing lithium manganese iron phosphate includes the following steps:

[0079] W1. Preparation of manganese iron oxide nanoparticles;

[0080] W2. Carbon coating of manganese iron oxide nanoparticles;

[0081] W3. Carbon-coated manganese iron oxide nanoparticles are sintered at 800℃ for 12 hours to obtain lithium manganese iron phosphate.

[0082] The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps:

[0083] X1. Mix 9 parts by weight of MnCl2, 6 parts by weight of FeCl2, 26 parts by weight of deionized water, 2 parts by weight of acrylic acid and 1 part by weight of lithium acrylate until dissolved to obtain a precursor solution;

[0084] X2. Filter the precursor solution, adjust the pH to 3.5, and preheat it at 80℃ for 15 minutes to obtain the pretreated precursor solution.

[0085] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 45 L / h and transported to a reactor for calcination at 800 °C to obtain manganese iron oxide nanoparticles.

[0086] The carbon coating described in step W2 includes the following steps:

[0087] Y1. Mix 50 parts by weight of manganese iron oxide nanoparticles with 30 parts by weight of lithium dihydrogen phosphate, 20 parts by weight of phosphoric acid, 40 parts by weight of glucose, 20 parts by weight of EDTA and 14 parts by weight of deionized water in a ball mill and ball mill to obtain carbon-coated manganese iron oxide nanoparticles.

[0088] Comparative Example 3

[0089] A method for preparing lithium manganese iron phosphate includes the following steps:

[0090] W1. Preparation of manganese iron oxide nanoparticles;

[0091] W2. Carbon coating of manganese iron oxide nanoparticles;

[0092] W3. Carbon-coated manganese iron oxide nanoparticles are sintered at 800℃ for 12 hours to obtain lithium manganese iron phosphate.

[0093] The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps:

[0094] X1. Mix 9 parts by weight of MnCl2, 6 parts by weight of FeCl2, 26 parts by weight of deionized water, 2 parts by weight of acrylic acid and 1 part by weight of lithium acrylate until dissolved to obtain a precursor solution;

[0095] X2. Filter the precursor solution, adjust the pH to 3.5, and preheat it at 80℃ for 15 minutes to obtain the pretreated precursor solution.

[0096] X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 45 L / h and transported to a reactor for calcination at 800 °C to obtain manganese iron oxide nanoparticles.

[0097] The carbon coating described in step W2 includes the following steps:

[0098] Y1. Mix 50 parts by weight of manganese iron oxide nanoparticles with 30 parts by weight of lithium dihydrogen phosphate, 20 parts by weight of phosphoric acid, 40 parts by weight of glucose, 20 parts by weight of lithium dodecyl sulfate and 14 parts by weight of deionized water in a ball mill and ball mill to obtain carbon-coated manganese iron oxide nanoparticles.

[0099] Performance testing

[0100] For the preparation of the positive electrode sheet, lithium manganese iron phosphate, conductive carbon black, and binder (PVDF) prepared in Examples 1-3 and Comparative Examples 1-3 were weighed in a mass ratio of 8:1:1, thoroughly ground and mixed evenly, and collected in a small beaker. An appropriate amount of N-methylpyrrolidone was added to the beaker to prepare a slurry of suitable viscosity. After magnetic stirring for 15 hours, the black slurry was evenly coated onto aluminum foil using a slurry coating machine. The aluminum foil coated with slurry was placed in a vacuum drying oven at 120°C and dried for 12 hours. After being removed, it was rolled and compacted by an electric roller press, and then cut into circular electrode sheets with a diameter of 13 mm using a slicing machine. The electrode sheets were vacuum dried at 120°C for 12 hours. After the moisture was fully dried, the mass of the electrode sheets was weighed using a precision balance and set aside for later use.

[0101] Half-cell assembly: The half-cell uses an organic electrolyte. The lithium metal sheet is sensitive to oxygen and moisture. The assembly process is completed in an argon-filled glove box. The half-cell uses 2032 button cell contacts. Before use, the battery casing is cleaned sequentially with detergent, ultrapure water, and anhydrous ethanol. A polypropylene membrane is used as the separator. Before use, the separator is cut into 18mm diameter circles using a slicer. A lithium metal sheet (Φ15.6*0.45) is used as the negative electrode of the button cell. The electrolyte formula is 1mol LiPF6-EC / DEC. The battery assembly process is as follows: The lithium sheet, separator, positive electrode sheet, gasket, spring, and positive electrode shell are pressed flat in sequence at the center of the negative electrode shell. Appropriate amounts of electrolyte are dripped onto both sides of the separator to wet them. After assembly, the battery is sealed using a button cell packaging machine. After standing for 15 hours, the corresponding electrochemical performance tests are performed.

[0102] Table 1. Performance indicators of lithium iron phosphate prepared by different processes in Examples 1-3 and Comparative Examples 1-3

[0103]

[0104]

[0105] The above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention in any way. Although the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications or alterations to the above-disclosed technical content to create equivalent embodiments without departing from the scope of the present invention. Any simple modifications, equivalent changes and alterations made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the scope of the present invention.

Claims

1. A method for producing a lithium iron manganese phosphate, characterized by, Includes the following steps: W1. Preparation of manganese iron oxide nanoparticles; W2. Carbon coating of manganese iron oxide nanoparticles; W3. Sinter the carbon-coated manganese iron oxide nanoparticles to obtain lithium manganese iron phosphate; The carbon coating described in step W2 includes the following steps: Y1. Manganese iron oxide nanoparticles were mixed with lithium dihydrogen phosphate, phosphoric acid, glucose, lithium dodecyl sulfate and deionized water in a ball mill and ball milled once to obtain a carbon-coated mixture; Y2. The carbon-coated mixture was mixed with glucose, EDTA and deionized water in a ball mill and then ball-milled a second time to obtain carbon-coated manganese iron oxide nanoparticles.

2. The method of claim 1, wherein the lithium iron manganese phosphate is prepared by the steps of: The preparation of the manganese iron oxide nanoparticles described in step W1 includes the following steps: ​ X1. Dissolve the manganese source and iron source in a solvent to obtain a precursor solution; X2. Filter the precursor solution, adjust the pH value, and preheat it to obtain a pretreated precursor solution; X3. The pretreated precursor solution is atomized to obtain an aerosol composed of tiny droplets. The aerosol spray flow rate is set to 10~50L / h, and the aerosol is transported to a reactor and calcined at 600~900℃ to obtain manganese iron oxide nanoparticles.

3. The method for preparing lithium manganese iron phosphate according to claim 2, characterized in that, The precursor solution described in step X1, by weight, consists of the following components: 5-9 parts MnCl2, 3-6 parts FeCl2, 22-26 parts deionized water, 1-2 parts acrylic acid, and 0.5-1 parts lithium acrylate.

4. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that, The sintering mentioned in step W3 refers to sintering carbon-coated manganese iron oxide nanoparticles at a temperature of 700~800℃ for 8~12 hours to obtain lithium manganese iron phosphate.

5. The method for preparing lithium manganese iron phosphate according to claim 2, characterized in that, In step X2, the pH value is <7, the preheating temperature is 60~100℃, and the preheating is continued for 10~15 minutes.

6. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that, The composition by weight is as follows: 30-50 parts of manganese iron oxide nanoparticles, 20-30 parts of lithium dihydrogen phosphate, 10-20 parts of phosphoric acid, 15-25 parts of glucose, 5-10 parts of lithium dodecyl sulfate, and 5-9 parts of deionized water.

7. The method for preparing lithium manganese iron phosphate according to claim 1, characterized in that, The carbon-coated mixture described in step Y2 comprises 30-50 parts by weight, glucose 10-15 parts by weight, EDTA 5-10 parts by weight, and deionized water 3-5 parts by weight.

8. A lithium manganese iron phosphate prepared by the preparation method according to any one of claims 1-7.

9. The lithium manganese iron phosphate according to claim 8, characterized in that, The lithium manganese iron phosphate is used as an electrode material.

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