Iron phosphate as well as preparation method therefor and use thereof

Abstract

Iron phosphate as well as a preparation method therefor and the use thereof. The method comprises: preparing a precursor solution from an iron source, a phosphate source, an amide substance and a first solvent, filling a mesoporous material with the precursor solution to form a filling body; then adding a second solvent which is immiscible with the first solvent and has a different density, and wrapping the filling body in the second solvent, so as to seal the precursor solution in the cavities or pore channels in the mesoporous material, such that the mesoporous material has blocking and limiting effects, and the precursor solution in the cavity or the pore channel can generate, after reaction, iron phosphate particles smaller than the volume of the cavity; and then calcinating same to remove the mesoporous material, so as to obtain discrete iron phosphate particles having a small particle size.

Description

Ferric phosphate and its preparation method and use Technical Field

[0001] The present invention relates to the field of battery materials and relates to iron phosphate and a preparation method and application thereof. Background Art

[0002] The positive electrode material is a key material that directly determines the energy density and safety of the battery. It affects the overall performance of the lithium-ion battery. Different types of positive electrode materials also bring about differences in performance.

[0003] Lithium iron phosphate (LiFePO4, also known as lithium iron phosphate, lithium iron phosphate, or LFP) is an important cathode material for lithium-ion batteries. Because it contains no precious elements like cobalt and utilizes abundant phosphorus, lithium, and iron resources, it offers advantages over other cathode materials, including a broad availability of raw materials, a stable supply, and low cost. Furthermore, it offers a moderate operating voltage (3.2V), a large capacity (170mAh / g), high discharge power, fast charging, a long cycle life, and excellent stability in high-temperature and thermal environments.

[0004] Lithium iron phosphate materials have occupied a place in the power battery market due to their excellent safety performance and low price. However, due to their low electronic conductivity (about 10 -9 S / cm) and ionic conductivity (about 10 -13 ~10 -16 S / cm) limits its high current charge and discharge capabilities. To address this issue, researchers have proposed various methods to improve the rate performance of lithium iron phosphate materials. Among them, reducing the particle size of lithium iron phosphate materials is a very effective method. By preparing small-sized lithium iron phosphate particles, the distance for ion diffusion can be effectively shortened, thereby achieving the goal of improving the rate performance of lithium iron phosphate.

[0005] As one of the key raw materials for preparing lithium iron phosphate, even small changes in the microstructure and chemical composition of iron phosphate (FePO4) can have a significant impact on its performance. Controlling the synthesis quality of iron phosphate materials and ensuring the stable production of small-sized iron phosphate materials and the uniformity and stability of their properties are crucial for preparing high-performance lithium iron phosphate materials. Therefore, developing a new method to control the particle size of iron phosphate to produce small-sized iron phosphate particles is of great significance.

[0006] Summary of the Invention

[0007] The following is a summary of the subject matter described in detail herein. This summary is not intended to limit the scope of the claims.

[0008] In view of the problems existing in the prior art, the purpose of the present disclosure is to provide an iron phosphate and its preparation method and use. The preparation method prepares a precursor solution obtained by preparing an iron source, a phosphate source, an amide substance and a first solvent and fills it into a mesoporous material to form a filling body, and then adds a second solvent that is immiscible with the first solvent and has a different density. The filling body is wrapped with the second solvent to seal the precursor solution in the cavity / pore in the mesoporous material. The mesoporous material produces a blocking and restricting effect, so that the precursor solution in the cavity can generate iron phosphate particles smaller than the volume of the cavity / pore after reaction. After removing the mesoporous material by calcination, discrete small-size iron phosphate particles can be obtained.

[0009] To achieve this goal, the present disclosure adopts the following technical solutions:

[0010] In a first aspect, the present disclosure provides a method for preparing ferric phosphate, the preparation method comprising:

[0011] Mixing a precursor solution with a mesoporous material to fill the mesoporous material with the precursor solution to form a filling body, thereby obtaining a filling body solution; the precursor solution includes an iron source, a phosphate source, an amide substance, and a first solvent;

[0012] mixing the filling body solution and the second solvent so that the second solvent covers the surface of the filling body to form a coating, thereby obtaining a coating body solution;

[0013] The coating solution is heated to react, thereby generating iron phosphate inside the coating to obtain a sealed body;

[0014] The sealed body is calcined to obtain iron phosphate.

[0015] The preparation method disclosed in the present invention uses a mesoporous material as a sacrificial template, mixes the mesoporous material with a precursor solution, and fills the pores or cavities of the mesoporous material with the precursor solution to form a filling body. A second solvent is then added to wrap the filling body, and the precursor solution outside the filling body is removed, and the precursor solution filled in the cavity inside is sealed, that is, the second solvent plays a role similar to an "oil seal" to obtain a coating body. It can be understood that the second solvent and the first solvent are insoluble in each other and have different densities (insoluble in each other), so that when the filling body is transferred to the second solvent, the second solvent can exclude the first solvent and cover the surface of the filling body; at this time, the coating body is heated, and the amide substance in the precursor solution filled in the cavity will decompose, thereby adjusting the pH of the sealed precursor solution so that the precursor solution reaches the conditions for generating iron phosphate to carry out the generation reaction. At this point, due to the presence of the mesoporous material, the growth of iron phosphate is physically restricted, resulting in small-sized lithium iron phosphate particles. Furthermore, due to the physical isolation provided by the mesoporous material, the iron phosphate grown in adjacent coatings will not merge and grow, thereby obtaining discrete small-particle iron phosphate. Finally, by calcination, the mesoporous material, which serves as a sacrificial template, is removed to obtain the final product. Therefore, the preparation method can control and adjust the particle size and is conducive to obtaining a discrete, non-agglomerated product.

[0016] It should be noted that the preparation method can mix the iron source, phosphate source, amide substance and the first solvent with the mesoporous material at the same time, or can first form a precursor solution, and then mix it with the mesoporous material, as long as the mixing is uniform and sufficient, the iron source, phosphate source, and amide substance can be completely dissolved to form a precursor solution, and the formed precursor solution can fill the cavity and pores of the mesoporous material to form a filling body. Therefore, the specific amount of the precursor solution and the mesoporous material can be adjusted according to actual conditions and needs. If the precursor solution is used too much, the excess precursor solution can be collected and mixed with new mesoporous material.

[0017] The following are optional technical solutions of the present disclosure, but are not intended to limit the technical solutions provided by the present disclosure. Through the following technical solutions, the technical objectives and beneficial effects of the present disclosure can be better achieved and realized.

[0018] As an optional technical solution disclosed in the present invention, the molar ratio of iron element, phosphate and amide group is 1:1:(1 to 1.8), and the amount of the iron source, phosphate source and amide substance is controlled, for example, 1:1:1, 1:1:1.5, 1:1:2, 1:1:2.5, 1:1:3, 1:1:3.5, 1:1:4, 1:1:4.5, 1:1:5, 1:1:5.5, 1:1:6, 1:1:6.5, 1:1:7, 1:1:7.5 or 1:1:8, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0019] In one embodiment, the amide substance includes any one of urea, formamide or acetamide, or a combination of at least two of them. Typical but non-limiting examples of the combination include a combination of urea and formamide, a combination of urea and acetamide, or a combination of formamide and acetamide.

[0020] Amides are used to decompose during subsequent heating, raising the solution pH to support the production of ferric phosphate. However, using too much of them can lead to the premature production of impurities such as ferric phosphate or ferric hydroxide in the precursor solution before heating.

[0021] In one embodiment, the iron source comprises a ferric salt.

[0022] In one embodiment, the ferric salt comprises ferric nitrate and / or ferric chloride.

[0023] In one embodiment, the phosphate source includes any one of sodium phosphate, ammonium hydrogen phosphate or ammonium dihydrogen phosphate, or a combination of at least two of them. Typical but non-limiting examples of the combination include a combination of sodium phosphate and ammonium hydrogen phosphate, a combination of sodium phosphate and ammonium dihydrogen phosphate, or a combination of ammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0024] In the present disclosure, an iron source and a phosphate source are used to generate iron phosphate.

[0025] As an optional technical solution of the present disclosure, the pH value of the precursor solution is 1 to 1.5, for example, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45 or 1.5, etc., but is not limited to the listed values, and other unlisted values ​​within the above numerical range are also applicable.

[0026] In one embodiment, the temperature of the precursor solution is ≤ 20°C.

[0027] Since the precursor solution contains amide substances, in order to inhibit the decomposition of amide substances before the precursor solution undergoes a heating reaction, the pH range needs to be adjusted to a strongly acidic range when the precursor solution is prepared. At this time, the temperature of the precursor solution can be lowered to further inhibit the decomposition of amide substances, thereby preventing the premature generation of iron phosphate and allowing the precursor solution to be smoothly filled into the mesoporous material.

[0028] As an optional technical solution of the present disclosure, the mesoporous material includes a mesoporous polymer.

[0029] Mesoporous polymers have strong capillary forces, which are conducive to filling the pores and cavities inside the mesoporous polymers with their precursor solutions.

[0030] In one embodiment, the mesoporous polymer comprises any one or a combination of at least two of a methacrylate polymer, a styrene polymer, or a styrene derivative polymer. Typical but non-limiting examples of the combination include a combination of a methacrylate polymer and a styrene polymer, a combination of a methacrylate polymer and a styrene derivative polymer, or a combination of a styrene polymer and a styrene derivative polymer. The polymer comprises a monomer or a copolymer.

[0031] In one embodiment, the mesoporous material is microsphere particles, and the particle size of the microsphere particles is 2 to 50 μm, for example, 2 μm, 5 μm, 8 μm, 10 μm, 12 μm, 15 μm, 18 μm, 20 μm, 22 μm, 25 μm, 28 μm, 30 μm, 32 μm, 35 μm, 38 μm, 40 μm, 42 μm, 45 μm, 48 μm or 50 μm, etc., but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0032] The precursor liquid that the mesoporous polymer can accommodate determines the liquid that participates in the reaction. Therefore, the particle size of the produced iron phosphate can be adjusted by regulating the particle size of the mesoporous conjugate microspheres, and iron phosphate products of 0.1 to 10 μm can be produced, such as 0.1 μm, 0.3 μm, 0.5 μm, 0.8 μm, 1 μm, 1.5 μm, 2 μm, 2.5 μm, 3 μm, 3.5 μm, 4 μm, 4.5 μm, 5 μm, 5.5 μm, 6 μm, 6.5 μm, 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm or 10 μm, etc., but are not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0033] As an optional technical solution of the present disclosure, the preparation method includes, when mixing the precursor solution and the mesoporous material, performing a vacuum treatment so that the precursor solution is filled in the mesoporous material.

[0034] In one embodiment, the vacuum degree of the vacuum treatment is 0.05 to 0.2 MPa, for example, 0.05 MPa, 0.08 MPa, 0.1 MPa, 0.12 MPa, 0.14 MPa, 0.16 MPa, 0.18 MPa or 0.2 MPa, etc., but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0035] The present disclosure can further promote the increase of the amount of precursor solution in the mesoporous material by applying vacuum, thereby ensuring the complete filling of the pores and cavities in the mesoporous material and increasing the output efficiency of iron phosphate.

[0036] As an optional technical solution of the present disclosure, the first solvent includes water.

[0037] In one embodiment, the second solvent comprises edible oil and / or liquid paraffin.

[0038] Since iron sources and phosphate sources are generally inorganic salts that dissolve in water, the first solvent includes water, which is also conducive to the dissolution of amide substances; the second solvent is selected to be a solvent that is immiscible with water to exclude water from the surface of the mesoporous material and thus act as an oil seal. Considering that organic solvents that are immiscible with water have certain volatility and toxicity, edible oil and / or liquid paraffin can be used. Of course, reasonable adjustments can also be made according to actual conditions.

[0039] As an optional technical solution disclosed in the present invention, the temperature of the heating reaction is 80-120°C, for example, 80°C, 83°C, 86°C, 89°C, 92°C, 95°C, 98°C, 100°C, 103°C, 106°C, 109°C, 112°C, 115°C, 118°C or 120°C, and the time is 2-4h, for example, 2h, 2.2h, 2.4h, 2.6h, 2.8h, 3h, 3.2h, 3.4h, 3.6h, 3.8h or 4h, but is not limited to the listed values, and other values ​​not listed within the above numerical range are also applicable.

[0040] The temperature of the heating reaction is the appropriate temperature for the production of ferric phosphate. When selecting this temperature, it should also be considered that the decomposition of amide substances can promote the increase of the pH value of the solution.

[0041] In one embodiment, the calcination temperature is 550-650°C, for example, 550°C, 560°C, 570°C, 580°C, 590°C, 600°C, 610°C, 620°C, 630°C, 640°C or 650°C, but is not limited to the listed values. Other values ​​not listed within the above numerical range are also applicable.

[0042] Within an appropriate range, the calcination temperature has little effect on the particle size of ferric phosphate.

[0043] As an optional technical solution of the present disclosure, the preparation method includes:

[0044] Using deionized water as the first solvent, first adjusting the pH of the deionized water to 1 with acid, adding an iron source, a phosphate source, and an amide substance under stirring, controlling the added amount according to the molar ratio of iron element, phosphate group, and amide group of 1:1:(1-1.8), then adjusting the pH to 1.0-1.5 with acid, maintaining the temperature below 20°C, to obtain a precursor solution;

[0045] Mesoporous styrene polymer microsphere particles with a particle size range of 2 to 50 μm are used as the mesoporous material, the mesoporous material is placed into the precursor solution, and the mixture is fully stirred. The precursor solution is filled into the mesoporous material by evacuating the mixture to a vacuum degree of 0.05 to 0.2 MPa to form a filling body, thereby obtaining a filling body solution.

[0046] Pour a second solvent into the filler solution, wherein the second solvent is immiscible with the first solvent and has a different density, so that the filler is transferred and immersed in the second solvent, and the second solvent covers the surface of the filler to form a coating, and after removing the liquid separated from the second solvent, a coating solution is obtained;

[0047] The coating solution is heated at 80-120° C. for 2-4 hours to generate iron phosphate nanoparticles inside the coating, and then cooled and filtered to obtain a sealed body;

[0048] The sealed body is calcined at 550-650° C., washed with water for multiple times and then dried to obtain discrete iron phosphate particles.

[0049] In a second aspect, the present disclosure provides an iron phosphate, which is obtained using the preparation method described in the first aspect.

[0050] In a third aspect, the present disclosure provides a lithium iron phosphate positive electrode material, which is prepared using the iron phosphate described in the second aspect.

[0051] Compared with the existing technical solutions, the present disclosure has at least the following beneficial effects:

[0052] The present disclosure provides a preparation method that can control the particle size of iron phosphate and obtain small-particle iron phosphate. The preparation method uses a mesoporous material as a sacrificial template, wraps a precursor solution inside, and then decomposes an amide substance to make the precursor solution reach the conditions for generating iron phosphate and carry out a generation reaction; at this time, the physical restriction and isolation effect of the mesoporous material can be used to effectively control the particle size of iron phosphate and obtain discrete small-particle iron phosphate.

[0053] Still other aspects will become apparent upon reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] The accompanying drawings are used to provide a further understanding of the technical solution of this article and constitute a part of the specification. Together with the embodiments of this application, they are used to explain the technical solution of this article and do not constitute a limitation to the technical solution of this article.

[0055] FIG1 is a scanning electron microscope test image of the ferric phosphate obtained in Example 1. DETAILED DESCRIPTION

[0056] The technical solution of the present disclosure is further illustrated below through specific implementation methods.

[0057] It should be apparent to those skilled in the art that the embodiments are only intended to help understand the present disclosure and should not be considered as specific limitations of the present disclosure.

[0058] Example 1

[0059] This embodiment provides a method for preparing iron phosphate, which comprises:

[0060] The pH of the deionized water solution was adjusted to 1 with nitric acid. Ferric nitrate was then added under stirring. After thorough mixing, sodium hydrogen phosphate was added, maintaining a molar ratio of 1:1 between ferric nitrate and sodium hydrogen phosphate. Urea was then added and thoroughly stirred, maintaining a molar ratio of 1:1:1.4 between ferric nitrate, sodium hydrogen phosphate, and urea. The pH of the solution was then adjusted to 1.2 with nitric acid. The temperature was maintained below 20°C during the process to form a precursor solution. Mesoporous polystyrene microspheres with a diameter of 20 μm were immersed in the precursor solution and thoroughly stirred. The solution was then vacuumed at 0.1 MPa for 15 minutes to form a filling body. Soybean oil was then introduced into the upper layer of the reaction liquid, and the lower layer of the reaction liquid was removed to form a coating body. The remaining liquid was heated to 80°C for 3 hours, cooled, filtered, and sealed. After calcination at 600°C for 30 minutes, the solution was washed with water, and dried at 110°C to obtain small, discrete iron phosphate particles.

[0061] Example 2

[0062] This embodiment provides a method for preparing iron phosphate, which comprises:

[0063] The pH of the deionized water solution was adjusted to 1 with hydrochloric acid. Ferric chloride was then added under stirring. After thorough mixing, ammonium hydrogen phosphate was added, maintaining a molar ratio of 1:1 between ferric chloride and ammonium hydrogen phosphate. Formamide was then added and thoroughly stirred, maintaining a molar ratio of 1:1:1 between ferric chloride, ammonium hydrogen phosphate, and formamide. The pH of the solution was then adjusted to 1 with hydrochloric acid. The temperature was maintained below 20°C during the process to form a precursor solution. Mesoporous polystyrene microspheres with a diameter of 50 μm were immersed in the precursor solution and thoroughly stirred. The solution was then vacuumed at 0.05 MPa for 15 minutes to form a filling body. Soybean oil was then introduced into the upper layer of the reaction liquid, and the lower layer of the reaction liquid was removed to form a coating body. The remaining liquid was heated to 120°C for 4 hours, cooled, filtered, and sealed. The solution was calcined at 650°C for 60 minutes, washed with water, and dried at 110°C to obtain small, discrete iron phosphate particles.

[0064] Example 3

[0065] This embodiment provides a method for preparing iron phosphate, which comprises:

[0066] The pH of the deionized water solution was adjusted to 1 with sulfuric acid. Ferric nitrate was then added under stirring. After thorough mixing, ammonium dihydrogen phosphate was added, maintaining a molar ratio of 1:1 between ferric chloride and ammonium dihydrogen phosphate. Acetamide was then added and thoroughly stirred, maintaining a molar ratio of 1:1:1.8 between ferric nitrate, ammonium dihydrogen phosphate, and acetamide. The pH of the solution was then adjusted to 1 with phosphoric acid. The temperature was maintained below 20°C during the process to form a precursor solution. Mesoporous polystyrene microspheres with a diameter of 2 μm were immersed in the precursor solution and thoroughly stirred. The solution was then vacuumed at 0.2 MPa for 15 minutes to form a filling body. Soybean oil was then introduced into the upper layer of the reaction liquid, and the lower layer of the reaction liquid was removed to form a coating body. The remaining liquid was heated to 100°C for 2 hours, cooled, filtered, and sealed. After calcination at 550°C for 120 minutes, the solution was washed with water, and dried at 110°C to obtain small, discrete iron phosphate particles.

[0067] Example 4

[0068] This embodiment provides a method for preparing iron phosphate, wherein the diameter of the mesoporous polystyrene microsphere particles is adjusted from 20 μm to 0.9 μm. Except for the above, other conditions are exactly the same as those in Example 1.

[0069] Example 5

[0070] This embodiment provides a method for preparing iron phosphate, wherein the diameter of the mesoporous polystyrene microsphere particles is adjusted from 20 μm to 2 μm. Except for the above, other conditions are exactly the same as those in Example 1.

[0071] Example 6

[0072] This embodiment provides a method for preparing iron phosphate, wherein the diameter of the mesoporous polystyrene microsphere particles is adjusted from 20 μm to 30 μm. Except for the above, other conditions are exactly the same as those in Example 1.

[0073] Example 7

[0074] This embodiment provides a method for preparing ferric phosphate, in which the vacuum degree of the vacuum treatment is adjusted from 0.1 MPa to 0.05 MPa. Except for the above, other conditions are exactly the same as those in Example 1.

[0075] Comparative Example 1

[0076] This comparative example provides a method for preparing ferric phosphate, which does not use amide substances, that is, does not use urea. Except for the above, other conditions are exactly the same as those in Example 1.

[0077] Comparative Example 2

[0078] This comparative example provides a method for preparing ferric phosphate, which does not use soybean oil as a second solvent. The obtained filler is directly subjected to a heating reaction, and then calcined and crushed. Except for the above, other conditions are exactly the same as those in Example 1.

[0079] Comparative Example 3

[0080] This comparative example provides a method for preparing iron phosphate, which does not use mesoporous materials, does not perform vacuum treatment, and does not use soybean oil as a second solvent. The obtained precursor solution is directly heated to react, and then calcined and crushed. Except for the above, other conditions are exactly the same as those in Example 1.

[0081] FIG1 is a scanning electron microscope test image of the iron phosphate obtained in Example 1. As can be seen from FIG1 , the obtained iron phosphate is spherical, the particles are discrete, and no agglomeration occurs. There are voids inside the particles left by mesoporous polystyrene microspheres, and the particle size is 2 to 4 μm.

[0082] The particle size of the iron phosphate obtained in the examples and comparative examples was tested, and the results are recorded in Table 1.

[0083] Table 1

[0084] As can be seen from Table 1:

[0085] By controlling the particle size of the mesoporous polymer, the particle size of the iron phosphate can be controlled; at the same time, it can be seen that the filling amount of the reaction solution in the cavity inside the mesopore can be increased by vacuuming, thereby changing the particle size of the iron phosphate.

[0086] Electrochemical performance test: The iron phosphate obtained in Example 1, Comparative Example 1 and Comparative Example 3 was loaded into a ball mill as a precursor raw material together with Li2CO3, and wet ball milled with anhydrous ethanol at a speed of 600 rpm for 5 hours; glucose, lithium carbonate and the prepared iron phosphate precursor in a molar ratio of 0.05:1.05:1.0 were calcined at 600°C under a nitrogen atmosphere to obtain lithium iron phosphate material.

[0087] The prepared lithium iron phosphate positive electrode material was mixed with a cyclohexane solution of acetylene black and polyvinylidene fluoride (PVDF) at room temperature and pressure to form a slurry (according to the positive electrode material: acetylene black: PVDF weight ratio of 75:15:10), and evenly coated on an aluminum foil substrate as the positive electrode of the simulated battery. The negative electrode of the simulated battery used a lithium sheet, and the electrolyte was 1 mol LiPF6 dissolved in a mixed solvent of 1L EC (ethylene carbonate) and DMC (dimethyl carbonate) (volume ratio 1:1). The positive electrode, negative electrode, electrolyte, and diaphragm were assembled into a simulated battery in an argon-protected glove box. The diaphragm was a polypropylene porous membrane. The rate test steps of the simulated battery were: first charged to 4.2V at 30mA / g, then discharged to 2.0V at a rate current. The capacity released was the discharge capacity at that rate. After the discharge was completed, it was discharged to 2.0V at 30mA / g. Then the next rate test was performed. The results are shown in Table 2:

[0088] Table 2

[0089] It can be seen from the above table that compared with Example 1, the iron phosphate precursor formed in Comparative Example 1 without adding urea at low pH has poor effect as a precursor material for lithium iron phosphate; and the precursor formed by Comparative Example 3 is crushed to obtain iron phosphate with uniform discrete particle size, and the performance of the obtained lithium iron phosphate is significantly worse.

Claims

1. A method for preparing iron phosphate, comprising: Mixing a precursor solution with a mesoporous material, filling the precursor solution inside the mesoporous material to form a filled body, and obtaining a filled body solution; The precursor solution includes an iron source, a phosphate source, an amide substance, and a first solvent; Mixing the filled body solution with a second solvent, covering the surface of the filled body with the second solvent to form a coated body, and obtaining a coated body solution; Subjecting the coated body solution to a heating reaction to generate iron phosphate inside the coated body, and obtaining a sealed body; Calcining the sealed body to obtain iron phosphate.

2. The preparation method according to claim 1, wherein, Controlling the amounts of the iron source, the phosphate source, and the amide substance according to a molar ratio of iron element, phosphate group, and amide group of 1:1:(1-1.8).

3. The preparation method according to claim 1 or 2, wherein, The amide substance includes any one or a combination of at least two of urea, formamide, or acetamide.

4. The preparation method according to any one of claims 1-3, wherein, The pH value of the precursor solution is 1-1.

5.

5. The preparation method according to any one of claims 1-4, wherein, The temperature of the precursor solution ≤ 20 °C.

6. The preparation method according to any one of claims 1-5, wherein, The mesoporous material includes a mesoporous polymer.

7. The preparation method according to claim 6, wherein, The mesoporous polymer includes any one or a combination of at least two of a methacrylate polymer, a styrene polymer, or a styrene derivative polymer.

8. The preparation method according to any one of claims 1-7, wherein, The mesoporous material is microsphere particles, and the particle size of the microsphere particles is 2-50 μm.

9. The preparation method according to any one of claims 1-8, wherein, The preparation method includes, when mixing the precursor solution with the mesoporous material, performing a vacuum treatment to fill the precursor solution inside the mesoporous material.

10. The preparation method according to claim 9, wherein, The degree of vacuum of the vacuum treatment is 0.05-0.2 MPa.

11. The preparation method according to any one of claims 1-10, wherein, The first solvent includes water.

12. The preparation method according to any one of claims 1-11, wherein, The second solvent includes edible oil and / or liquid paraffin.

13. The preparation method according to any one of claims 1-12, wherein, The temperature of the heating reaction is 80-120 °C, and the time is 2-4 h.

14. The preparation method according to any one of claims 1-13, wherein, The temperature of the calcination is 550-650 °C, and the time is 0.5-2 h.

15. The preparation method according to any one of claims 1-14, wherein, The preparation method includes: Using deionized water as the first solvent, first adjust the pH of the deionized water to 1 with an acid. While stirring, add an iron source, a phosphate source, and an amide substance, and control the addition amount according to the molar ratio of iron element, phosphate group, and amide group of 1:1:(1-1.8). Then adjust the pH to 1.0-1.5 with an acid, and keep the temperature below 20°C to obtain a precursor solution; Using mesoporous styrene polymer microsphere particles with a particle size range of 2-50 μm as the mesoporous material, put the mesoporous material into the precursor solution, stir well, and evacuate to a vacuum degree of 0.05-0.2 MPa to make the precursor solution fill inside the mesoporous material to form a filled body, and obtain a filled body solution; Pour a second solvent into the filled body solution. The second solvent is immiscible with the first solvent and has a different density, so that the filled body is transferred and immersed in the second solvent, and the second solvent covers the surface of the filled body to form a coated body. After removing the liquid that is layered with the second solvent, a coated body solution is obtained; Heat the coated body solution at 80-120°C for 2-4 h to generate iron phosphate nanoparticles inside the coated body. After cooling and filtering, a sealed body is obtained; Calcine the sealed body at 550-650°C for 0.5-2 h, wash it with water multiple times and then dry it to obtain discrete iron phosphate particles.

16. An iron phosphate obtained by using the preparation method according to any one of claims 1-15.

17. A lithium iron phosphate cathode material prepared by using the iron phosphate according to claim 16.

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