Iron phosphate and a method for its preparation and use

Abstract

The present disclosure belongs to the field of battery materials. The present disclosure provides a kind of iron phosphate and its preparation method and use, the preparation method is obtained by preparing precursor solution with iron source, phosphate source, amide substance and first solvent, and is filled in mesoporous material, forms filling body, then adds second solvent which is not mutually soluble with first solvent and different in density, and the precursor solution is sealed in the cavity or channel inside mesoporous material by using second solvent to wrap filling body, mesoporous material produces blocking and limiting effect, so that the precursor solution in cavity or channel can generate iron phosphate particles smaller than cavity volume after reaction, and after removing mesoporous material by calcination, discrete small particle size iron phosphate particles can be obtained.

Description

TECHNICAL FIELD

[0001] The present disclosure belongs to the field of battery materials, and relates to a kind of iron phosphate and its preparation method and use. BACKGROUND

[0002] The positive electrode material is the key material directly determining the energy density and safety of battery, which influences the comprehensive performance of lithium ion battery, and different kinds of positive electrode materials also bring the difference of performance.

[0003] Lithium iron phosphate (molecular formula LiFePO4, Lithium Iron Phosphate, also known as lithium iron phosphate, lithium iron phosphate, abbreviated as LFP), is an important positive electrode material of lithium ion battery. Because it does not contain cobalt and other valuable elements, the reserves and content of phosphorus, lithium and iron resources used are rich, therefore, compared with other positive electrode materials, lithium iron phosphate has the advantages of wide raw material, stable supply, low cost and the like. Moreover, its working voltage is moderate (3.2V), and the electric capacity is large (170mAh / g), and it also has the advantages of high discharge power, fast charging, long cycle life, high stability in high temperature and high heat environment and the like.

[0004] Lithium iron phosphate material occupies a place in the power battery market due to its excellent safety performance and low price. However, due to its low electronic conductivity (about 10 -9 S / cm) and ion conductivity (about 10 -13 ~ 10 -16 S / cm), the large current charging and discharging capacity is restricted. In order to solve this problem, people have proposed various methods to improve the rate performance of lithium iron phosphate material, among which reducing the particle size of lithium iron phosphate material is a very effective method. By preparing small size lithium iron phosphate particles, the ion diffusion distance can be effectively shortened, so as to achieve the purpose of improving the rate performance of lithium iron phosphate.

[0005] It can be seen that as one of the important raw materials for preparing lithium iron phosphate, the slight change of microstructure and chemical composition of iron phosphate (FePO4) will have a great influence on the performance of lithium iron phosphate. Controlling the synthesis quality of iron phosphate material and ensuring the stable production and uniform and stable properties of small size iron phosphate material are very crucial for preparing high performance lithium iron phosphate material. Therefore, it is of great significance to develop a new method for controlling the particle size of iron phosphate to prepare small size iron phosphate particles. SUMMARY

[0006] 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.

[0007] In view of the problems in the prior art, the purpose of the present disclosure is to provide a kind of iron phosphate and its preparation method and use, the preparation method is filled in mesoporous material by the precursor solution of iron source, phosphate source, amide substance and first solvent preparation, form filling body, again join the second solvent that is not mutually soluble with first solvent and different in density, the filling body is wrapped by using second solvent, make precursor solution seal in the cavity / pore channel of mesoporous material, mesoporous material generates barrier and limiting effect, so that the precursor solution in cavity can generate the iron phosphate particle smaller than the volume of cavity / pore channel after reaction, again through calcination after removing mesoporous material, discrete small particle size iron phosphate particle can be obtained.

[0008] To achieve this purpose, the present disclosure uses the following technical solutions:

[0009] In a first aspect, the present disclosure provides a preparation method of iron phosphate, the preparation method comprising:

[0010] Mixing precursor solution and mesoporous material, so that the precursor solution is filled in the mesoporous material to form a filling body, and a filling body solution is obtained; the precursor solution comprises an iron source, a phosphate source, an amide substance and a first solvent;

[0011] Mixing the filling body solution and the second solvent to form a coating body by covering the surface of the filling body with the second solvent, and obtaining a coating body solution;

[0012] Heating the coating body solution to generate iron phosphate in the interior of the coating body, and obtaining a sealed body;

[0013] Calcining the sealed body to obtain iron phosphate.

[0014] The preparation method of the present disclosure uses mesoporous materials as a sacrificial template, mixes the mesoporous materials with a precursor solution, fills the precursor solution in the pores or cavities of the mesoporous materials to form a filling body, then adds a second solvent to wrap the filling body, removes the precursor solution outside the filling body, and seals the precursor solution filled in the cavities, that is, the second solvent plays a role similar to an "oil seal", thereby obtaining a coated body. It can be understood that the second solvent and the first solvent are immiscible and have different densities (not miscible), so that when the filling body is transferred to the second solvent, the second solvent can expel the first solvent and cover the surface of the filling body. At this time, heating the coated body, 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 condition for generating iron phosphate to carry out the generation reaction. At this time, due to the presence of mesoporous materials, the growth of iron phosphate is physically limited, and small particle size lithium iron phosphate particles can be obtained. Due to the physical isolation effect of the mesoporous materials, the iron phosphate grown in adjacent coated bodies will not merge and grow, so that small particle size iron phosphate in discrete form is obtained. Finally, by calcining, the mesoporous materials as the sacrificial template are removed to obtain the final product. Therefore, the preparation method can control and adjust the particle size, and is beneficial to obtain discrete and non-agglomerated products.

[0015] It should be noted that the preparation method can mix the iron source, phosphate source, amide substance and first solvent with the mesoporous materials at the same time, or can first form a precursor solution and then mix it with the mesoporous materials, as long as the mixture 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 cavities and pores of the mesoporous materials to form a filling body. Therefore, the specific amount of the precursor solution and the mesoporous materials can be adjusted according to the actual situation and needs. For example, if the amount of the precursor solution is too much, the excess precursor solution can be collected and mixed with new mesoporous materials for use.

[0016] The following is an optional technical solution of the present disclosure, but is not a limitation of the technical solution provided by the present disclosure. Through the following technical solution, the technical purpose and beneficial effects of the present disclosure can be better achieved and realized.

[0017] As an optional technical solution of the present disclosure, the amount of the iron source, phosphate source and amide substance is controlled according to the molar ratio of iron element, phosphate and amide group being 1:1:(1-1.8), 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, but is not limited to the listed values. Other values not listed in the above value range are also applicable.

[0018] 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.

[0019] The amide substance is decomposed when heated later, increasing the pH of the solution to support the generation of ferric phosphate. However, if the amount of the amide substance is too large, it can cause the generation of impurities such as ferric phosphate or ferric hydroxide in the precursor solution before heating.

[0020] In one embodiment, the iron source includes a ferric salt.

[0021] In one embodiment, the ferric salt includes ferric nitrate and / or ferric chloride.

[0022] 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.

[0023] In the present disclosure, the iron source and the phosphate source are used to generate ferric phosphate.

[0024] As an optional technical solution of the present disclosure, the pH value of the precursor solution is 1-1.5, for example, 1, 1.05, 1.1, 1.15, 1.2, 1.25, 1.3, 1.35, 1.4, 1.45 or 1.5, but is not limited to the listed values. Other values not listed in the above value range are also applicable.

[0025] In one embodiment, the temperature of the precursor solution is ≤20℃.

[0026] Since the precursor solution contains an amide substance, in order to inhibit the decomposition of the amide substance before the precursor solution is heated, the pH range needs to be adjusted to be strongly acidic when the precursor solution is prepared. At this time, the temperature of the precursor solution can be reduced to further inhibit the decomposition of the amide substance, thereby preventing the premature generation of ferric phosphate and allowing the precursor solution to be smoothly filled into the mesoporous material.

[0027] As an optional technical solution of the present disclosure, the mesoporous material includes a mesoporous polymer.

[0028] The mesoporous polymer has strong capillary force, which is beneficial to fill the precursor solution into the pores and cavities inside the mesoporous polymer.

[0029] In one embodiment, the mesoporous polymer comprises any one of a methacrylate polymer, a styrene polymer, a styrene derivative polymer, or a combination of at least two of them, typical but non-limiting examples of which 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 can comprise a homopolymer or a copolymer.

[0030] In one embodiment, the mesoporous material is a microsphere particle, and the particle size of the microsphere particle is 2-50 μm, such as 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 not limited to the listed values, and other values not listed within the above range are also applicable.

[0031] The precursor liquid that can be accommodated by the mesoporous polymer determines the liquid involved in the reaction, and thus the particle size of the iron phosphate product can be adjusted by regulating the particle size of the mesoporous composite microsphere, and iron phosphate products with a particle size of 0.1-10 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 not limited to the listed values, and other values not listed within the above range are also applicable.

[0032] As an optional technical solution of the present disclosure, the preparation method comprises, when mixing the precursor solution and the mesoporous material, performing vacuum treatment to fill the precursor solution into the mesoporous material.

[0033] In one embodiment, the vacuum degree of the vacuum treatment is 0.05-0.2 MPa, such as 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 not limited to the listed values, and other values not listed within the above range are also applicable.

[0034] The present disclosure can further increase the amount of the precursor solution in the mesoporous material by applying vacuum to ensure complete filling of the pores and cavities in the mesoporous material and increase the production efficiency of iron phosphate.

[0035] As an optional technical solution of the present disclosure, the first solvent comprises water.

[0036] In an embodiment, the second solvent comprises edible oil and / or liquid paraffin.

[0037] Since the iron source and the phosphate source are generally inorganic salts, which are dissolved in water, the first solvent comprises water, which is also beneficial for the dissolution of the amide substance; the second solvent is selected to be a solvent that is not miscible with water, so as to exclude water on the surface of the mesoporous material, thereby playing the role of an oil seal; considering that the organic solvent that is not miscible with water has certain volatility and toxicity, edible oil and / or liquid paraffin can be selected, and of course, reasonable adjustment can be made according to actual conditions.

[0038] As an optional technical solution of the present disclosure, the temperature of the heating reaction is 80-120℃, for example, 80℃, 83℃, 86℃, 89℃, 92℃, 95℃, 98℃, 100℃, 103℃, 106℃, 109℃, 112℃, 115℃, 118℃ or 120℃, 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 not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0039] The temperature of the heating reaction is a suitable temperature for the production of iron phosphate, and when selecting this temperature, the decomposition of the amide substance to promote the increase of the pH value of the solution should also be considered.

[0040] In an embodiment, the calcination temperature is 550-650℃, for example, 550℃, 560℃, 570℃, 580℃, 590℃, 600℃, 610℃, 620℃, 630℃, 640℃ or 650℃, but not limited to the listed values, and other values not listed in the above numerical range are also applicable.

[0041] Within a suitable range, the calcination temperature has little effect on the particle size of the iron phosphate.

[0042] As an optional technical solution of the present disclosure, the preparation method comprises:

[0043] Deionized water is used as the first solvent, the pH of the deionized water is first adjusted to 1 using an acid, and the iron source, the phosphate source and the amide substance are added under stirring, the addition amount is controlled according to the molar ratio of iron element, phosphate and amide group being 1:1:(1-1.8), and then the pH is adjusted to 1.0-1.5 using an acid, and the temperature is maintained below 20℃, to obtain a precursor solution;

[0044] The mesoporous styrene polymer microsphere particles with a particle size range of 2-50 μm are used as the mesoporous material, the mesoporous material is put into the precursor solution, and the precursor solution is filled in the mesoporous material by stirring and vacuumizing to a vacuum degree of 0.05-0.2 MPa, so as to form a filling body, and a filling body solution is obtained;

[0045] The second solvent is poured into the filling body solution, the second solvent is immiscible with the first solvent and has a different density, so that the filling body is transferred and immersed in the second solvent, and the second solvent covers the surface of the filling body to form a coating body, and after the liquid layered with the second solvent is removed, a coating body solution is obtained;

[0046] The coating body solution is subjected to a heating reaction at 80-120 ℃ for 2-4 h, so as to generate iron phosphate nanoparticles in the interior of the coating body, and after cooling and filtration, an encapsulation body is obtained;

[0047] The encapsulation body is calcined at 550-650 ℃, and after multiple water washing and drying, discrete iron phosphate particles are obtained.

[0048] In a second aspect, the present disclosure provides an iron phosphate obtained by the preparation method of the first aspect.

[0049] In a third aspect, the present disclosure provides a lithium iron phosphate positive electrode material prepared by using the iron phosphate of the second aspect.

[0050] Compared with the prior art, the present disclosure has at least the following beneficial effects:

[0051] The present disclosure provides a preparation method capable of controlling the particle size of iron phosphate and obtaining small-particle-size iron phosphate, which uses a mesoporous material as a sacrificial template, a precursor solution is wrapped in the interior, and then a generation reaction is performed by decomposition of an amide substance to make the precursor solution reach the condition for generating iron phosphate; at this time, the mesoporous material plays a physical limiting and isolating role, so as to effectively control the particle size of the iron phosphate and obtain discrete small-particle-size iron phosphate.

[0052] Other aspects can be apparent to those of ordinary skill in the art after reading and understanding the accompanying drawings and detailed description. BRIEF DESCRIPTION OF DRAWINGS

[0053] The accompanying drawings are used to provide a further understanding of the technical solutions of the present disclosure, and constitute a part of the specification, and are used together with the embodiments of the present disclosure to explain the technical solutions of the present disclosure, and do not constitute a limitation on the technical solutions of the present disclosure.

[0054] Figure 1 FIG. 1 is a scanning electron microscope test diagram of the iron phosphate obtained in Example 1. DETAILED DESCRIPTION

[0055] The technical solutions of the present disclosure are further illustrated below through specific embodiments.

[0056] Those skilled in the art should understand that the embodiments are only used to help understand the present disclosure and should not be regarded as specific limitations of the present disclosure.

[0057] Embodiment 1

[0058] The present embodiment provides a preparation method of iron phosphate, which comprises the following steps:

[0059] The pH of a deionized water solution is adjusted to 1 with nitric acid, and then ferric nitrate is added under stirring. After fully stirring and mixing, sodium hydrogen phosphate is added, so as to keep the molar ratio of ferric nitrate and sodium hydrogen phosphate at 1:1. Urea is then added and fully stirred and mixed, so as to keep the molar ratio of ferric nitrate, sodium hydrogen phosphate and urea at 1:1:1.4. The pH of the solution is adjusted to 1.2 with nitric acid, and the temperature is kept below 20℃ during the process, so as to form a precursor solution. Mesoporous polystyrene microsphere particles with a diameter of 20μm are immersed in the precursor solution, and after fully stirring, vacuum treatment is performed at a vacuum degree of 0.1MPa for 15min, so as to form a filling body. Then, soybean oil is introduced into the upper layer of the reaction liquid, and the lower layer of the reaction liquid is removed, so as to form a coating body. The remaining liquid is heated to 80℃ for a heating reaction of 3h, and then the sealing body is obtained through cooling and filtration. After calcination at 600℃ for 30min, and then water washing and drying at 110℃, small-particle dispersed iron phosphate particles are obtained.

[0060] Embodiment 2

[0061] The present embodiment provides a preparation method of iron phosphate, which comprises the following steps:

[0062] The pH of a deionized water solution is adjusted to 1 with hydrochloric acid, and then ferric chloride is added under stirring. After fully stirring and mixing, ammonium hydrogen phosphate is added, so as to keep the molar ratio of ferric chloride and ammonium hydrogen phosphate at 1:1. Formamide is then added and fully stirred and mixed, so as to keep the molar ratio of ferric chloride, ammonium hydrogen phosphate and formamide at 1:1:1. The pH of the solution is adjusted to 1 with hydrochloric acid, and the temperature is kept below 20℃ during the process, so as to form a precursor solution. Mesoporous polystyrene microsphere particles with a diameter of 50μm are immersed in the precursor solution, and after fully stirring, vacuum treatment is performed at a vacuum degree of 0.05MPa for 15min, so as to form a filling body. Then, soybean oil is introduced into the upper layer of the reaction liquid, and the lower layer of the reaction liquid is removed, so as to form a coating body. The remaining liquid is heated to 120℃ for a heating reaction of 4h, and then the sealing body is obtained through cooling and filtration. After calcination at 650℃ for 60min, and then water washing and drying at 110℃, small-particle dispersed iron phosphate particles are obtained.

[0063] Embodiment 3

[0064] The embodiment provides a preparation method of iron phosphate, and the preparation method comprises the following steps:

[0065] The pH of a deionized water solution is adjusted to 1 by using sulfuric acid, and then iron nitrate is added under stirring. After the mixture is fully stirred, ammonium dihydrogen phosphate is added, so that the molar ratio of ferric chloride to ammonium dihydrogen phosphate is 1:1. Then, acetamide is added and fully stirred, so that the molar ratio of iron nitrate, ammonium dihydrogen phosphate and acetamide is 1:1:1.8. The pH of the solution is adjusted to 1 by using phosphoric acid, and the temperature is kept below 20 DEG C during the process. A precursor solution is formed. Mesoporous polystyrene microsphere particles with a diameter of 2 microns are immersed in the precursor solution, and after being fully stirred, vacuum treatment is performed at a vacuum degree of 0.2 MPa for 15 minutes to form a filling body. Then, soybean oil is introduced into the upper layer of the reaction liquid, and the lower layer of the reaction liquid is removed to form a coating body. The remaining liquid is heated to 100 DEG C for a heating reaction of 2 hours, and then a storage body is obtained through cooling and filtration. After calcination at 550 DEG C for 120 minutes and water washing, the storage body is dried at 110 DEG C to obtain small-particle discrete iron phosphate particles.

[0066] Example 4

[0067] The embodiment provides a preparation method of iron phosphate, wherein the diameter of mesoporous polystyrene microsphere particles is adjusted from 20 microns to 0.9 microns, and other conditions are completely same as those in Example 1.

[0068] Example 5

[0069] The embodiment provides a preparation method of iron phosphate, wherein the diameter of mesoporous polystyrene microsphere particles is adjusted from 20 microns to 2 microns, and other conditions are completely same as those in Example 1.

[0070] Example 6

[0071] The embodiment provides a preparation method of iron phosphate, wherein the diameter of mesoporous polystyrene microsphere particles is adjusted from 20 microns to 30 microns, and other conditions are completely same as those in Example 1.

[0072] Example 7

[0073] The embodiment provides a preparation method of iron phosphate, wherein the vacuum degree of vacuum treatment is adjusted from 0.1 MPa to 0.05 MPa, and other conditions are completely same as those in Example 1.

[0074] Comparative Example 1

[0075] The comparative example provides a preparation method of iron phosphate, wherein no amide substance is used, that is, no urea is used, and other conditions are completely same as those in Example 1.

[0076] Comparative Example 2

[0077] The present comparative example provides a preparation method of iron phosphate, which does not use the second solvent soybean oil, directly carries out a heating reaction on the obtained filling body, and then carries out calcination and crushing, and other conditions are completely same as Example 1.

[0078] Comparative Example 3

[0079] The present comparative example provides a preparation method of iron phosphate, which does not use mesoporous materials, does not carry out vacuumizing treatment, and does not use the second solvent soybean oil, directly carries out a heating reaction on the obtained precursor solution, and then carries out calcination and crushing, and other conditions are completely same as Example 1.

[0080] Figure 1 The scanning electron microscope test diagram of the iron phosphate obtained in Example 1 is shown in FIG. 1. Figure 1 It can be seen from FIG. 1 that the obtained iron phosphate is spherical, the particles are in a discrete state, and no agglomeration occurs, the particles have voids left by the mesoporous polystyrene microspheres inside, and the particle size is 2-4 μm.

[0081] The particle size of the iron phosphate obtained in the examples and comparative examples is tested, and the results are recorded in Table 1.

[0082] Table 1

[0083] Group Iron phosphate particle size (pm) Example 1 2～4 Example 2 5～10 Example 3 0.2～0.4 Example 4 0.05～0.15 Example 5 0.1～0.35 Example 6 0.8～2 Example 7 1.5～3.5 Comparative Example 1 2～4 Comparative Example 2 Agglomerate Comparative Example 3 Agglomerate

[0084] It can be seen from Table 1 that:

[0085] By controlling the particle size of the mesoporous polymer to be small, the particle size of the iron phosphate can be controlled; at the same time, it can be seen that by the action of vacuumizing, the filling amount of the reaction solution in the mesoporous cavity can be increased, so that the particle size of the iron phosphate changes.

[0086] Electrochemical performance test: the iron phosphate obtained in Example 1, Comparative Example 1 and Comparative Example 3 is used as a precursor raw material and loaded into a ball mill with Li2CO3, and wet ball milling is carried out at a speed of 600 rpm for 5 h; glucose, lithium carbonate and the obtained iron phosphate precursor are mixed in a molar ratio of 0.05:1.05:1.0, and a lithium iron phosphate material is obtained by calcination at 600°C under a nitrogen atmosphere.

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

[0088] Table 2

[0089]

[0090] As can be seen from the above table, compared with Example 1, Comparative Example 1 did not add urea, and the iron phosphate precursor formed at low pH had poor effect as a precursor material for lithium iron phosphate; and the precursor formed in Comparative Example 3 could not be broken to obtain uniform particle size of iron phosphate, and the obtained lithium iron phosphate had significantly poorer performance.

Claims

1. A method for preparing ferric phosphate, comprising: The precursor solution is mixed with the mesoporous material, so that the precursor solution fills the interior of the mesoporous material to form a filler, and the filler solution is obtained. The precursor solution includes an iron source, a phosphate source, an amide substance, and a first solvent; A filler solution is mixed with a second solvent, the second solvent being immiscible with the first solvent and having 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, thus obtaining a coating solution; The coating solution is heated to react, and iron phosphate is generated inside the coating to obtain the encapsulated body; The sealed body was calcined to obtain iron phosphate.

2. The preparation method according to claim 1, wherein, The amount of iron source, phosphate source and amide substance is controlled according to the molar ratio of iron element, phosphate and amide group of 1:1:(1~1.8).

3. The preparation method according to claim 1, wherein, The amides include any one or a combination of at least two of urea, formamide, or acetamide.

4. The preparation method according to claim 1, wherein, The pH value of the precursor solution is 1 to 1.

5.

5. The preparation method according to claim 1, wherein, The temperature of the precursor solution is ≤20℃.

6. The preparation method according to claim 1, wherein, The mesoporous material includes mesoporous polymers.

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

8. The preparation method according to claim 1, wherein, The mesoporous material is microspheres with a particle size of 2~50μm.

9. The preparation method according to claim 1, wherein, The preparation method includes, during the mixing of precursor solution and mesoporous material, vacuum treatment is performed to allow the precursor solution to fill the mesoporous material.

10. The preparation method according to claim 9, wherein, The vacuum level of the vacuuming process is 0.05~0.2MPa.

11. The preparation method according to claim 1, wherein, The first solvent includes water.

12. The preparation method according to claim 1, wherein, The second solvent includes edible oil and / or liquid paraffin.

13. The preparation method according to claim 1, wherein, The heating reaction is carried out at a temperature of 80~120℃ for 2~4 hours.

14. The preparation method according to claim 1, wherein, The calcination temperature is 550~650℃, and the time is 0.5~2h.

15. The preparation method according to claim 1, wherein, The preparation method includes: Using deionized water as the first solvent, the pH of the deionized water is first adjusted to 1 with acid. Iron source, phosphate source and amide substances are added under stirring. The amount added is controlled according to the molar ratio of iron element, phosphate and amide group is 1:1:(1~1.8). The pH is then adjusted to 1.0~1.5 with acid, and the temperature is kept below 20℃ to obtain the precursor solution. Mesoporous styrene polymer microspheres with a particle size range of 2~50μm are used as mesoporous materials. The mesoporous materials are placed into the precursor solution and stirred thoroughly. The vacuum is then drawn to a vacuum degree of 0.05~0.2MPa to fill the mesoporous materials with the precursor solution, forming a filler body, and thus obtaining the filler body solution. A second solvent is poured into the filler solution. The second solvent is immiscible with the first solvent and has a different density. The filler is transferred and immersed in the second solvent. The second solvent covers the surface of the filler to form a coating. After removing the liquid that is separated from the second solvent, the coating solution is obtained. The coating solution was heated at 80~120℃ for 2~4h to generate iron phosphate nanoparticles inside the coating. After cooling and filtration, the encapsulated body was obtained. The sealed body was calcined at 550~650℃ for 0.5~2h, washed with water multiple times, and then dried to obtain discrete iron phosphate particles.

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