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CN116477594B - Modified lithium iron manganese phosphate positive electrode material and preparation method and application thereof - Google Patents

Modified lithium iron manganese phosphate positive electrode material and preparation method and application thereof Download PDF

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CN116477594B
CN116477594B CN202310470936.XA CN202310470936A CN116477594B CN 116477594 B CN116477594 B CN 116477594B CN 202310470936 A CN202310470936 A CN 202310470936A CN 116477594 B CN116477594 B CN 116477594B
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CN116477594A (en
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高茹月
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Hubei Eve Power Co Ltd
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    • C01B25/00—Phosphorus; Compounds thereof
    • C01B25/16—Oxyacids of phosphorus; Salts thereof
    • C01B25/26—Phosphates
    • C01B25/45—Phosphates containing plural metal, or metal and ammonium
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01B—NON-METALLIC ELEMENTS; COMPOUNDS THEREOF; METALLOIDS OR COMPOUNDS THEREOF NOT COVERED BY SUBCLASS C01C
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    • H—ELECTRICITY
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    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M10/00—Secondary cells; Manufacture thereof
    • H01M10/05—Accumulators with non-aqueous electrolyte
    • H01M10/052—Li-accumulators
    • H01M10/0525—Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01M—PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY
    • H01M4/00—Electrodes
    • H01M4/02—Electrodes composed of, or comprising, active material
    • H01M4/13—Electrodes for accumulators with non-aqueous electrolyte, e.g. for lithium-accumulators; Processes of manufacture thereof
    • H01M4/136—Electrodes based on inorganic compounds other than oxides or hydroxides, e.g. sulfides, selenides, tellurides, halogenides or LiCoFy
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    • 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
    • C—CHEMISTRY; METALLURGY
    • C01—INORGANIC CHEMISTRY
    • C01P—INDEXING SCHEME RELATING TO STRUCTURAL AND PHYSICAL ASPECTS OF SOLID INORGANIC COMPOUNDS
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    • C01P2004/80—Particles consisting of a mixture of two or more inorganic phases
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    • 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
    • H01M2004/026—Electrodes composed of, or comprising, active material characterised by the polarity
    • H01M2004/028—Positive electrodes
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Abstract

The invention provides a modified lithium iron manganese phosphate positive electrode material, and a preparation method and application thereof, wherein the preparation method comprises the following steps: (1) Mixing the cationic resin with a first manganese source, a first iron source and a zinc source to obtain a mixed material; (2) Mixing the mixture after heat treatment with a phosphorus source, adding potassium salt, a lithium source, a second manganese source and a second iron source, stirring, adding a carbon source, and drying to obtain a solid material; (3) The solid material is sintered to obtain the modified lithium iron manganese phosphate positive electrode material, and the Zn-doped lithium iron manganese phosphate positive electrode material with high conductivity is developed, so that the intrinsic conductivity of the obtained composite positive electrode material is improved, and the composite positive electrode material has excellent multiplying power performance and cycle performance.

Description

Modified lithium iron manganese phosphate positive electrode material and preparation method and application thereof
Technical Field
The invention belongs to the technical field of lithium ion batteries, and relates to a modified lithium iron manganese phosphate positive electrode material, a preparation method and application thereof.
Background
With the increasing energy crisis, lithium ion secondary batteries have been considered as the most promising energy conversion and storage devices, where lithium iron phosphate has been attracting attention due to its low price, strong safety, high cycle stability and environmental friendliness, but its low energy density has limited application in new energy electric vehicles. By doping manganese into the lithium iron phosphate material to synthesize the lithium iron manganese phosphate solid solution material, the energy density of the lithium iron phosphate can be improved, so that the lithium iron manganese phosphate is an excellent energy storage material with high energy density and high safety.
Although lithium iron manganese phosphate has a high voltage plateau and energy density, it is poor in ion conductivity and electron conductivity, resulting in poor rate performance; and the Jahn-teller effect generated by Mn 3+ ions during the reaction and the dissolution of Mn during the reaction can lead to a drastic reduction in the electrochemical properties of the material, especially the long-term cycling properties. At present, the electrochemical performance of the lithium iron manganese phosphate is improved mainly by controlling the particle morphology, nanocrystallization, ion doping and other means.
CN115535993a discloses a lithium iron manganese phosphate positive electrode material and a preparation method thereof, comprising: adding iron powder into phosphoric acid solution; adding manganese carbonate into the first reaction mixed solution; grinding the second reaction mixed solution; adding lithium hydroxide to carry out grinding treatment; adding a carbon source to carry out grinding treatment; spray granulating to obtain carbon-coated lithium iron manganese phosphate particles; and calcining the carbon-coated lithium iron manganese phosphate particles to obtain the lithium iron manganese phosphate anode material.
CN115810736a discloses a lithium iron manganese phosphate positive electrode material and a preparation method thereof, wherein a liquid phase method is utilized to uniformly coat metal salt and organic carbon source on the surface of the lithium iron manganese phosphate material, carbonization is carried out at high temperature, and a metal/carbon composite coating layer is formed on the surface of the lithium iron manganese phosphate material; then organic small molecules with Lewis acid/base groups are respectively modified on the surfaces of lithium manganese iron phosphate material particles with different particle diameters through coordination bonds, and the surface-modified lithium manganese iron phosphate material is obtained after drying; and finally, mixing the lithium iron manganese phosphate material particles with different particle sizes according to a proportion to obtain the lithium iron manganese phosphate positive electrode material with proper particle size and uniform distribution.
The method aims at the problem of poor conductivity of lithium iron manganese phosphate, and mainly aims at the research and modification directions of the method to optimize the coating of the material surface, such as sucrose and carbon black, but the method does not improve the intrinsic conductivity of the lithium iron manganese phosphate, only improves the ion and electron conductivity of the particle interface, and does not aim at modification of a microscopic level.
Disclosure of Invention
The invention aims to provide a modified lithium iron manganese phosphate positive electrode material, a preparation method and application thereof, and develops a high-conductivity Zn-doped lithium iron manganese phosphate positive electrode material, and the obtained composite positive electrode material has improved intrinsic conductivity and excellent multiplying power performance and cycle performance.
In order to achieve the aim of the invention, the invention adopts the following technical scheme:
In a first aspect, the invention provides a preparation method of a modified lithium iron manganese phosphate anode material, which comprises the following steps:
(1) Mixing the cationic resin with a first manganese source, a first iron source and a zinc source to obtain a mixed material;
(2) Mixing the mixture obtained in the step (1) with a phosphorus source after heat treatment, adding potassium salt, a lithium source, a second manganese source and a second iron source, stirring, adding a carbon source, and drying to obtain a solid material;
(3) And (3) sintering the solid material obtained in the step (2) to obtain the modified lithium iron manganese phosphate anode material.
According to the method, the Mn/Fe/Zn metal ions are adsorbed in a sufficient amount by utilizing the cationic resin, are subjected to high-temperature carbonization and then are preliminarily coated, the Mn/Fe/Zn metal ions are used as a carrier, and the surface of the carrier is further transited to the inside of the carbon layer by the hole and crystal defects after Zn doping, and the secondary carbon of a carbon source.
Preferably, the cationic resin of step (1) is treated with a weak acid.
Preferably, the weak acid treated treatment agent comprises phosphoric acid and/or hydrochloric acid.
Preferably, the concentration of the treating agent is 0.002 to 0.007mol/L, for example: 0.002mol/L, 0.003mol/L, 0.004mol/L, 0.005mol/L, 0.006mol/L or 0.007mol/L, etc.
Preferably, the cationic resin is stirred during the mixing of step (1).
Preferably, the stirring speed is 300 to 500rpm, for example: 300rpm, 350rpm, 400rpm, 450rpm, 500rpm, etc.
Preferably, the first manganese source of step (1) comprises any one or a combination of at least two of manganese chloride, manganese nitrate or manganese sulphate.
Preferably, the iron source comprises any one or a combination of at least two of ferrous chloride, ferrous nitrate or ferrous sulfate.
Preferably, the zinc source comprises any one or a combination of at least two of zinc chloride, zinc nitrate or zinc sulphate.
Preferably, the zinc source is added in an amount of 20 to 30% of the total mass of the iron source and the manganese source, for example: 20%, 22%, 25%, 28% or 30%, etc.
Preferably, the mixing is followed by stirring, suction filtration, washing and drying.
Preferably, the stirring time is 4 to 6 hours, for example: 4h, 4.5h, 5h, 5.5h, 6h, etc.
Preferably, the washed detergent comprises deionized water.
Preferably, the temperature of the heat treatment in step (2) is 550 to 650 ℃, for example: 550 ℃, 580 ℃, 600 ℃, 620 ℃, 650 ℃, etc.
Preferably, the heat treatment is performed for a period of 1 to 3 hours, for example: 1h, 1.5h, 2h, 2.5h or 3h, etc.
Preferably, the heat treatment is followed by grinding, washing and vacuum drying treatments.
Preferably, the grinding time is 0.8 to 1.2 hours, for example: 0.8h, 0.9h, 1h, 1.1h, 1.2h, etc.
Preferably, the washed detergent comprises a 50% aqueous ethanol solution.
Preferably, the temperature of the vacuum drying treatment is 45 to 60 ℃, for example: 45 ℃, 48 ℃, 50 ℃, 55 ℃ or 60 ℃ and the like.
Preferably, the time of the vacuum drying treatment is 2 to 4 hours, for example: 2h, 2.5h, 3h, 3.5h or 4h, etc.
Preferably, the phosphorus source of step (2) comprises phosphoric acid.
Preferably, the phosphoric acid has a concentration of 15 to 30%, for example: 15%, 18%, 20%, 25% or 30%, etc.
Preferably, the lithium source comprises lithium carbonate.
Preferably, the second manganese source comprises manganese carbonate.
Preferably, the second iron source comprises iron phosphate.
Preferably, the potassium salt is added in an amount of 3 to 5%, for example: 3%, 3.5%, 4%, 4.5% or 5%, etc.
In the invention, potassium salt is added in the step (2) to form a eutectic salt system, and the particle growth can be prevented from being too large in the subsequent calcination process.
Preferably, the stirring speed is 700 to 1000rpm, for example: 700rpm, 800rpm, 900rpm, 1000rpm, etc.
Preferably, the stirring time is 3 to 5 hours, for example: 3h, 3.5h, 4h, 4.5h, 5h, etc.
Preferably, the carbon source comprises glucose.
Preferably, the carbon source is added in an amount of 20 to 30%, for example: 20%, 22%, 25%, 28% or 30%, etc.
Preferably, the filtration is performed before the drying.
Preferably, the drying temperature is 45-60 ℃, for example: 45 ℃, 48 ℃, 50 ℃, 55 ℃ or 60 ℃ and the like.
Preferably, the drying time is 2 to 4 hours, for example: 2h, 2.5h, 3h, 3.5h or 4h, etc.
Preferably, the sintering treatment of step (3) includes one-step sintering and two-step sintering.
Preferably, the temperature of the one-step sintering is 300 to 400 ℃, for example: 300 ℃, 320 ℃, 350 ℃, 380 ℃ or 400 ℃ and the like.
Preferably, the temperature rising speed of the one-step sintering is 3-5 ℃/min, for example: 3 ℃/min, 3.5 ℃/min, 4 ℃/min, 4.5 ℃/min or 5 ℃/min, etc.
Preferably, the one-step sintering time is 1 to 3 hours, for example: 1h, 1.5h, 2h, 2.5h or 3h, etc.
Preferably, the two-step sintering temperature is 700 to 800 ℃, for example: 700 ℃, 720 ℃, 750 ℃, 780 ℃ or 800 ℃ and the like.
Preferably, the temperature rising speed of the two-step sintering is 5-10 ℃/min, for example: 5 ℃/min, 6 ℃/min, 7 ℃/min, 8 ℃/min, 9 ℃/min or 10 ℃/min, etc.
Preferably, the two-step sintering time is 1 to 2 hours, for example: 1h, 1.2h, 1.5h, 1.8h, 2h, etc.
Preferably, the sintering treatment is followed by an acid washing and drying treatment.
In a second aspect, the present invention provides a modified lithium iron manganese phosphate cathode material, prepared by the method of the first aspect.
In a third aspect, the invention provides a positive electrode sheet comprising the modified lithium iron manganese phosphate positive electrode material according to the second aspect.
In a fourth aspect, the present invention provides a lithium ion battery comprising the positive electrode sheet according to the third aspect.
Compared with the prior art, the invention has the following beneficial effects:
(1) According to the invention, metal is doped after high-temperature carbonization after metal ion adsorption by utilizing cationic resin, a large number of holes are formed due to doping, so that an LMFP ion adsorption channel and sites are further enhanced, meanwhile, zn can be in a molten state at high temperature, the primary limiting effect on the metal ions is realized, the dissolution of the metal ions can be effectively prevented after secondary carbon coating, and the macroscopic LMFP intrinsic conductivity is improved.
(2) The modification method only involves liquid phase mixing and high-temperature sintering, has a simple structure and operability, and is suitable for large-scale production.
(3) The discharge capacity of the modified lithium iron manganese phosphate anode material prepared by the invention can reach more than 1580mAh/g, the discharge capacity of 3A/g can reach more than 1460mAh/g, the discharge capacity of 5A/g can reach more than 1320mAh/g, and the capacity retention rate of 200 cycles can reach more than 96.4%.
Detailed Description
The technical scheme of the invention is further described by the following specific embodiments. It will be apparent to those skilled in the art that the examples are merely to aid in understanding the invention and are not to be construed as a specific limitation thereof.
Example 1
The embodiment provides a modified lithium iron manganese phosphate anode material, which is prepared by the following steps:
(1) Putting 50mg of phosphoric acid-treated cationic resin with the concentration of 0.005mol/L into a 100ml beaker, adding MnCl 2, feCl 2 and ZnCl 2 aqueous solution with the mol ratio of Mn to Fe=6:4 at the rotation speed of 400rpm at 25 ℃, stirring for 5 hours, carrying out suction filtration, washing with deionized water for several times, and drying to obtain a mixed material;
(2) Putting the mixed material into a tube furnace, heating to 600 ℃ from normal temperature at 5 ℃/min in an inert atmosphere, keeping the temperature for 2 hours, taking out and grinding the mixed material to powder, washing the mixed material with 50% ethanol water solution for several times, drying the mixed material at 50 ℃ in vacuum for 3 hours, dissolving the mixed material in 20% H 3PO4 solution, then sequentially adding KCl, li 2CO3、MnCO3 and FePO 4, wherein the addition amount of Li is Mn and Fe=1:1:1, KCl is 3.5%, stirring the mixed material at 25 ℃ at the rotating speed of 800rpm for 4 hours, adding 25% glucose, continuously stirring the mixed material for 2 hours, and vacuum drying the mixed material at 50 ℃ for 3 hours to obtain a solid material;
(3) Grinding the solid material for 30min, then placing the ground solid material into a tube furnace, heating to 350 ℃ from normal temperature at 4 ℃/min in an inert atmosphere, keeping the temperature for 2h, heating to 750 ℃ at 8 ℃/min, keeping the temperature for 1.5h, pickling and drying to finally obtain the modified lithium iron manganese phosphate anode material.
Example 2
The embodiment provides a modified lithium iron manganese phosphate anode material, which is prepared by the following steps:
(1) Putting 0.005mol/L hydrochloric acid treated cationic resin into a 100ml beaker, adding MnCl 2, feCl 2 and ZnCl 2 aqueous solution according to the mol ratio of Mn to Fe=6:4 at the rotation speed of 400rpm at 25 ℃, stirring for 5h, filtering, washing with deionized water for several times, and drying to obtain a mixed material;
(2) Placing the mixed material into a tube furnace, heating to 620 ℃ from normal temperature at 5 ℃/min in an inert atmosphere, keeping the temperature for 2 hours, taking out and grinding the mixed material into powder, washing the powder with 50% ethanol water solution for several times, drying the powder at 50 ℃ in vacuum for 3 hours, dissolving the powder in 22% H 3PO4 solution, then sequentially adding KCl, li 2CO3、MnCO3 and FePO 4, wherein Li is Mn, fe=1:1:1.5, the adding amount of KCl is 3.5%, stirring the powder for 4 hours at the rotating speed of 780rpm, adding 20-30% glucose, continuously stirring the powder for 2 hours, filtering, and vacuum drying the powder at 50 ℃ for 3 hours to obtain a solid material;
(3) Grinding the solid material for 30min, then placing the ground solid material into a tube furnace, heating to 360 ℃ from normal temperature at 4 ℃/min in an inert atmosphere, keeping the temperature for 2h, heating to 780 ℃ at 8 ℃/min, keeping the temperature for 1.5h, pickling and drying to finally obtain the modified lithium iron manganese phosphate anode material.
Example 3
This example differs from example 1 only in that the zinc source is added in an amount of 15% of the total mass of the iron source and the manganese source, and other conditions and parameters are exactly the same as in example 1.
Example 4
This example differs from example 1 only in that the zinc source is added in an amount of 35% of the total mass of the iron source and the manganese source, and other conditions and parameters are exactly the same as in example 1.
Example 5
This example differs from example 1 only in that the temperature of the one-step sintering is 250 ℃, and other conditions and parameters are exactly the same as in example 1.
Example 6
This example differs from example 1 only in that the temperature of the one-step sintering is 450 ℃, and other conditions and parameters are exactly the same as in example 1.
Example 7
This example differs from example 1 only in that the two-stage sintering temperature is 650 ℃, and other conditions and parameters are exactly the same as in example 1.
Example 8
This example differs from example 1 only in that the two-stage sintering temperature is 850 ℃, and other conditions and parameters are exactly the same as example 1.
Comparative example 1
This comparative example differs from example 1 only in that no ion exchange resin was added, and other conditions and parameters were exactly the same as example 1.
Comparative example 2
This comparative example differs from example 1 only in that no potassium salt was added, and other conditions and parameters were exactly the same as in example 1.
Performance test: charging the prepared lithium ion battery with a current density of 1A/g for 1.5V, and discharging to 0.01V with current densities of 1A/g, 3A/g and 5A/g respectively to obtain discharge capacities under different multiplying powers, performing cycle test with a 1C/1C multiplying power, wherein the discharge capacities and cycle performance under different multiplying powers are shown in Table 1
TABLE 1
As can be seen from Table 1, the 1A/g discharge capacity of the battery prepared from the modified lithium iron manganese phosphate positive electrode material disclosed by the invention can reach more than 1580mAh/g, the 3A/g discharge capacity can reach more than 1460mAh/g, the 5A/g discharge capacity can reach more than 1320mAh/g, and the capacity retention rate of 200 cycles can reach more than 96.4%.
As can be seen from comparison of examples 1 and examples 3 to 4, in the preparation process of the modified lithium iron manganese phosphate anode material, the addition amount of a zinc source influences the performance of the modified lithium iron manganese phosphate anode material, the addition amount of the zinc source is controlled to be 20-30% of the total mass of an iron source and a manganese source, the modified lithium iron manganese phosphate anode material has good performance, if the addition amount of the zinc source is too low, the prepared carrier is insufficient in pore-forming, and if the addition amount of the zinc source is too high, the performance of the prepared material is slightly reduced, and raw materials are wasted.
As can be seen from comparison of examples 1 and examples 5 to 6, in the preparation process of the modified lithium manganese iron phosphate positive electrode material, the performance of the modified lithium manganese iron phosphate positive electrode material is affected by the temperature of one-step sintering, the temperature of one-step sintering is controlled to be 300-400 ℃, the modified lithium manganese iron phosphate positive electrode material has better performance, if the temperature of one-step sintering is too low, carbonization is incomplete, and if the temperature of one-step sintering is too high, particles are easy to increase, so that the activity is affected.
As can be seen from comparison of examples 1 and examples 7 to 8, in the preparation process of the modified lithium iron manganese phosphate positive electrode material, the performance of the modified lithium iron manganese phosphate positive electrode material is affected by the two-step sintering temperature, the two-step sintering temperature is controlled to be 700-800 ℃, the modified lithium iron manganese phosphate positive electrode material has good performance, if the two-step sintering temperature is too low, carbonization is incomplete, and if the two-step sintering temperature is too high, particles are easy to increase, so that activity is affected.
The method is characterized in that the cationic resin is used for carrying out sufficient adsorption on Mn/Fe/Zn metal ions, the Mn/Fe/Zn metal ions are carbonized at high temperature and then are preliminarily coated to be used as a carrier, and the hole and crystal defects after Zn doping enable the surface adsorption LMFP ions to further transition into the inside of the carbon layer, so that the cycle performance is improved.
As can be seen from the comparison of example 1 and comparative example 2, the present invention adds potassium salt in step (2) to form a eutectic salt system, which can prevent too large particle growth during subsequent calcination.
The applicant declares that the above is only a specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and it should be apparent to those skilled in the art that any changes or substitutions that are easily conceivable within the technical scope of the present invention disclosed by the present invention fall within the scope of the present invention and the disclosure.

Claims (40)

1. The preparation method of the modified lithium iron manganese phosphate anode material is characterized by comprising the following steps of:
(1) Mixing the cationic resin with a first manganese source, a first iron source and a zinc source to obtain a mixed material;
(2) Mixing the mixture obtained in the step (1) with a phosphorus source after heat treatment, adding potassium salt, a lithium source, a second manganese source and a second iron source, stirring, adding a carbon source, and drying to obtain a solid material;
(3) Sintering the solid material obtained in the step (2) to obtain the modified lithium iron manganese phosphate anode material;
The temperature of the heat treatment in the step (2) is 550-650 ℃.
2. The method of claim 1, wherein the cationic resin of step (1) is weak acid treated.
3. The method of claim 2, wherein the weak acid treated treatment agent comprises phosphoric acid and/or hydrochloric acid.
4. The method according to claim 3, wherein the concentration of the treating agent is 0.002 to 0.007mol/L.
5. The method of claim 1, wherein the cationic resin is stirred during the mixing of step (1).
6. The method according to claim 5, wherein the stirring speed is 300 to 500rpm.
7. The method of claim 1, wherein the source of manganese in step (1) comprises any one or a combination of at least two of manganese chloride, manganese nitrate, or manganese sulfate.
8. The method of claim 1, wherein the source of iron of step (1) comprises any one or a combination of at least two of ferrous chloride, ferrous nitrate, or ferrous sulfate.
9. The method of claim 1, wherein the zinc source of step (1) comprises any one or a combination of at least two of zinc chloride, zinc nitrate, or zinc sulfate.
10. The preparation method according to claim 1, wherein the zinc source in the step (1) is added in an amount of 20 to 30% of the total mass of the iron source and the manganese source.
11. The method of claim 1, wherein the mixing in step (1) is followed by stirring, suction filtration, washing and drying.
12. The method of claim 11, wherein the stirring is for a period of 4 to 6 hours.
13. The method of claim 11, wherein the washed detergent comprises deionized water.
14. The method according to claim 1, wherein the time of the heat treatment in the step (2) is 1 to 3 hours.
15. The method according to claim 1, wherein the heat treatment in step (2) is followed by grinding, washing and vacuum drying.
16. The method of claim 15, wherein the milling is for a period of 0.8 to 1.2 hours.
17. The method of claim 15, wherein the washed detergent comprises a 50% aqueous ethanol solution.
18. The method according to claim 15, wherein the vacuum drying treatment is carried out at a temperature of 45 to 60 ℃.
19. The method according to claim 15, wherein the time of the vacuum drying treatment is 2 to 4 hours.
20. The method of claim 1, wherein the phosphorus source of step (2) comprises phosphoric acid.
21. The method of claim 20, wherein the concentration of phosphoric acid is 15-30%.
22. The method of claim 1, wherein the lithium source of step (2) comprises lithium carbonate.
23. The method of claim 1, wherein the second source of manganese of step (2) comprises manganese carbonate.
24. The method of claim 1, wherein the second iron source of step (2) comprises iron phosphate.
25. The process according to claim 1, wherein the potassium salt is added in the amount of 3 to 5% in step (2).
26. The method according to claim 1, wherein the stirring speed in the step (2) is 700 to 1000rpm.
27. The method according to claim 1, wherein the stirring time in the step (2) is 3 to 5 hours.
28. The method of claim 1, wherein the carbon source of step (2) comprises glucose.
29. The method according to claim 1, wherein the carbon source is added in an amount of 20 to 30% in step (2).
30. The method of claim 1, wherein the step (2) is performed by filtration prior to the drying.
31. The process according to claim 1, wherein the drying in step (2) is carried out at a temperature of 45 to 60 ℃.
32. The method of claim 1, wherein the drying in step (2) is performed for a period of 2 to 4 hours.
33. The method of claim 1, wherein the sintering treatment of step (3) comprises a one-step sintering and a two-step sintering.
34. The method of claim 33, wherein the one-step sintering is performed at a temperature of 300 to 400 ℃.
35. The method of claim 33, wherein the one-step sintering is performed at a rate of 3 to 5 ℃/min.
36. The method of claim 33, wherein the one-step sintering is performed for a period of 1 to 3 hours.
37. The method of claim 33, wherein the two-step sintering is performed at a temperature of 700 to 800 ℃.
38. The method of claim 33, wherein the two-step sintering is performed at a rate of 5 to 10 ℃/min.
39. The method of claim 33, wherein the two-step sintering is performed for a period of 1 to 2 hours.
40. The method of claim 33, wherein the sintering process is followed by an acid wash and a bake process.
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