A cluster of iron phosphate, its preparation method and application

Abstract

This invention discloses a clustered iron phosphate, its preparation method, and its applications, belonging to the field of materials technology. The method involves pre-constructing a polyaniline-based block copolymer with a specific morphology. During subsequent mixing with iron phosphate raw materials, the hydrophilic / hydrophobic groups and coordination enrichment effects result in a clearly regular clustered iron phosphate. This material, when further prepared into lithium iron phosphate, not only effectively reduces the lithium-ion transport distance but also significantly improves structural stability. Simultaneously, the polyaniline-based block copolymer transforms into a carbon bonding layer, forming a uniformly bonded conductive network and enhancing the overall conductivity of the product. This invention also discloses a clustered lithium iron phosphate material prepared from the aforementioned clustered iron phosphate.

Description

Technical Field

[0001] This invention relates to the field of materials technology, and in particular to a cluster of iron phosphate, its preparation method, and its application. Background Technology

[0002] Lithium iron phosphate (LFP) is one of the main cathode materials for lithium-ion batteries, boasting advantages such as high safety, low production cost, and environmental friendliness. However, its insufficient conductivity and poor low-temperature performance severely limit its application. Therefore, it is necessary to modify or optimize LFP.

[0003] Most existing lithium iron phosphate (LFP) materials improve their performance defects by coating LFP with an outer layer or incorporating it into devices. However, this approach requires sophisticated processes and equipment, and achieving uniform modification at the microscopic level is challenging. Therefore, some researchers have designed special structures and morphologies for iron phosphate, the main precursor in LFP preparation. This design can be inherited by the final LFP product, effectively solving the problem of uniform microscopic modification. However, existing LFP products prepared from modified iron phosphate materials still fail to achieve a balanced equilibrium between conductivity and stability, and have not shown significant breakthroughs in low-temperature performance. Summary of the Invention

[0004] The purpose of this invention is to overcome the shortcomings of the prior art and provide a method for preparing clustered iron phosphate. This method involves pre-constructing a polyaniline-based block copolymer with a special morphology. When mixed with iron phosphate raw materials, the hydrophilic / hydrophobic groups and coordination enrichment effects result in iron phosphate exhibiting a distinctly regular clustered structure. After further preparation into lithium iron phosphate, this material not only effectively reduces the lithium-ion transport distance but also significantly improves structural stability. Simultaneously, the polyaniline-based block copolymer it contains is transformed into a carbon bonding layer, thereby forming a uniformly bonded conductive network and improving the overall conductivity of the product.

[0005] To achieve the above objectives, the technical solution adopted in this paper is as follows:

[0006] A method for preparing clustered iron phosphate includes the following steps:

[0007] A toluene solution of polyethylene glycol and a toluene solution of diisocyanate are mixed, and the resulting mixture is heated to 100-120°C and kept at that temperature for 5-6 hours to obtain a modified polyethylene glycol solution.

[0008] A p-phenylenediamine solution was added to the modified polyethylene glycol solution and mixed and reacted for 5-6 hours. Diethyl ether was added to the resulting mixture to cause a precipitation reaction. After the reaction was complete, the resulting mixture was filtered, washed and dried to obtain an intermediate solid product.

[0009] The intermediate solid product was dissolved in an organic solvent. After adjusting the pH of the resulting solution to 1-2, aniline monomer and initiator were added. The resulting mixture was mixed and reacted under a protective atmosphere for 8-10 hours, while the reaction temperature was controlled at 0-5°C. The resulting emulsion was filtered to obtain a solid product, washed, and dried to obtain a polyaniline block copolymer.

[0010] The polyaniline block copolymer was added to water and the pH of the resulting mixture was adjusted to 1.6-2.2. Then, an iron source and a phosphoric acid source were added and reacted for 2-6 hours. The resulting mixture was filtered to obtain the solid product, washed, and dried to obtain the iron phosphate precursor.

[0011] The iron phosphate precursor is heated to 500-700°C under a protective atmosphere and held for 4-10 hours to obtain the clustered iron phosphate.

[0012] In the preparation process of the clustered iron phosphate described in this invention, firstly, toluene diisocyanate (TDI) bonds are formed by grafting diisocyanate onto the end positions of polyethylene glycol. Then, p-phenylenediamine is introduced for further grafting to form an intermediate solid product containing a composite structure of p-phenylenediamine-TDI-polyethylene glycol. Finally, aniline monomer is introduced, and a monomer polymerization reaction is initiated under the action of an initiator, ultimately yielding a tri-block polymer containing a polyaniline-p-phenylenediamine-TDI-polyethylene glycol structure. When this polymer is dispersed in water, because polyethylene glycol is hydrophilic and polyaniline is hydrophobic, it exhibits a structure with polyaniline segments as the core and polyethylene glycol segments as the core. The shell consists of petal-shaped micelles. When an iron source and a phosphoric acid source are further introduced, the ether bonds in the polyethylene glycol segment will undergo a coordination reaction with the iron, thereby enriching the iron source near the micelles. Finally, using these micelles as templates, iron phosphate with a distinct cluster structure is generated. Since this clustered iron phosphate has a larger specific surface area than conventional flake or other particulate iron phosphate, when it is further used to prepare lithium iron phosphate materials, it can fully contact and wet the electrolyte, which is beneficial to the transport of lithium ions. On the other hand, the cluster structure is also more conducive to the rapid insertion and extraction of lithium ions and the improvement of structural stability. Therefore, the product has excellent rate performance and low-temperature performance.

[0013] Furthermore, the block copolymer used as a template is transformed into an internally cross-linked conductive carbon network during the subsequent calcination preparation of lithium iron phosphate materials, which greatly improves the conductivity of the product, resulting in a high insertion / extraction capacity.

[0014] In some embodiments, the average molecular weight of the polyethylene glycol is 5000 to 25000.

[0015] More preferably, the polyethylene glycol is at least one of PEG6000, PEG8000, PEG10000, PEG12000, PEG15000, PEG18000, and PEG20000.

[0016] More preferably, the polyethylene glycol is at least one of PEG8000, PEG10000, PEG12000, PEG15000, and PEG18000.

[0017] In some embodiments, the molar ratio of polyethylene glycol to diisocyanate is 1:(2 to 2.5).

[0018] More preferably, the diisocyanate is at least one selected from methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and methylene dicyclohexyl diisocyanate.

[0019] At the stated molar ratio, polyethylene glycol can fully react with diisocyanate to form a cyano-amino group and form grafted TDI at the terminal hydroxyl group of polyethylene glycol.

[0020] In some embodiments, the mass ratio of polyethylene glycol to toluene in the polyethylene glycol toluene solution is (1-5):10.

[0021] In some embodiments, the mass ratio of diisocyanate to toluene in the diisocyanate toluene solution is (1-5):10.

[0022] In some embodiments, the molar ratio of modified polyethylene glycol in the modified polyethylene glycol solution to p-phenylenediamine in the p-phenylenediamine solution is 1:(2-3).

[0023] Under the specified ratio, p-phenylenediamine can be grafted onto the cyano group of the modified polyethylene glycol TDI via amino groups, thereby forming a diblock structure.

[0024] In some embodiments, the organic solvent in which the intermediate solid product is dissolved is at least one of chloroform and N,N-dimethylformamide.

[0025] In some embodiments, the initiator is a ferric chloride solution, more preferably a primary solution of ferric chloride.

[0026] In some embodiments, the mass ratio of the intermediate solid product to the aniline monomer is (2.2–7):6.

[0027] More preferably, the concentration of the aniline monomer in the mixture is 4–6 mol / L.

[0028] More preferably, the molar ratio of the aniline monomer to the initiator is 1:(2-6).

[0029] In some embodiments, the solid-liquid ratio of the polyaniline block copolymer after adding water is 2 to 3 mg / mL.

[0030] In some embodiments, the iron source is at least one of ferric nitrate and ferric chloride.

[0031] More preferably, the mass ratio of the polyaniline block copolymer to the iron source is 1:(3-5).

[0032] When polyaniline-based block copolymers are used as template materials, if their content is too high after contacting the iron source, the mass ratio of the conductive network formed subsequently will be large, resulting in a reduction in the actual capacity of the product. At the same time, it may cause material agglomeration, which is not ideal for the construction of cluster morphology. If the content is too low, the degree of construction of iron phosphate cluster morphology is insufficient, and the mass ratio of the conductive network formed subsequently is low, which also reduces the conductivity of the product. In summary, the cluster morphology of iron phosphate prepared from the raw materials with the above-mentioned preferred ratio is the most ideal, and the comprehensive electrochemical performance of the lithium iron phosphate material prepared further is the best.

[0033] In some embodiments, the iron source is pre-prepared as a solution before being added to the mixture for the reaction, and the molar concentration of the iron source in the solution is 0.1 to 3 mol / L.

[0034] In some embodiments, the phosphoric acid source is at least one of ammonium phosphate, ammonium hydrogen phosphate, ammonium dihydrogen phosphate, and phosphoric acid.

[0035] In some embodiments, the phosphoric acid source is pre-prepared as a solution before being added to the mixture for the reaction, and the molar concentration of the phosphoric acid source in the solution is 0.1 to 3 mol / L.

[0036] In some embodiments, the molar ratio of iron in the iron source to phosphorus in the phosphate source is 1:(0.98~1).

[0037] In some embodiments, the protective atmosphere is at least one of nitrogen, helium, and argon.

[0038] Another object of the present invention is to provide clustered iron phosphate prepared by the aforementioned preparation method.

[0039] Another object of the present invention is to provide a clustered lithium iron phosphate material, which is prepared from the clustered lithium iron phosphate described in the present invention.

[0040] The clustered iron phosphate of this invention contains both iron phosphate and polyaniline block copolymer. When further used to prepare lithium iron phosphate material, the resulting product can effectively inherit the special morphology of clustered iron phosphate. At the same time, the polyaniline block copolymer can also be transformed into a nitrogen-containing internal cross-linked conductive network layer. This structure will greatly improve the conductivity of the product and effectively overcome the defects of traditional lithium iron phosphate materials with poor conductivity, but conventional existing modifications such as external coating cannot achieve uniformity of micro-modification of the material.

[0041] In some embodiments, the method for preparing the clustered lithium iron phosphate includes the following steps:

[0042] Clustered iron phosphate and lithium source are mixed and ground, and the resulting mixture is heated to 600-850℃ and held for 6-15 hours under a protective atmosphere to obtain the clustered lithium iron phosphate material.

[0043] In some embodiments, the lithium source is at least one of lithium carbonate, lithium hydroxide, and hydrated lithium hydroxide.

[0044] In some embodiments, the molar ratio of lithium in the lithium source to iron in the clustered iron phosphate is (0.8–1.2):(0.8–1.2).

[0045] Another object of the present invention is to provide a lithium-ion battery, including a positive electrode, said positive electrode comprising the clustered lithium iron phosphate material described in the present invention.

[0046] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0047] This invention provides a method for preparing clustered iron phosphate. The method involves pre-constructing a polyaniline-based block copolymer with a specific morphology. During subsequent mixing with iron phosphate raw materials, the hydrophilic / hydrophobic groups and coordination enrichment result in a clearly defined, regular clustered structure of the prepared iron phosphate. This material, when further processed into lithium iron phosphate, not only effectively reduces the lithium-ion transport distance but also significantly improves structural stability. Simultaneously, the polyaniline-based block copolymer transforms into a carbon bonding layer, forming a uniformly bonded conductive network and enhancing the overall conductivity of the product. This invention also provides clustered lithium iron phosphate materials prepared from the aforementioned clustered iron phosphate. Attached Figure Description

[0048] Figure 1 This is a scanning electron microscope image of the clustered iron phosphate prepared by the preparation method described in Example 1 of the present invention. Detailed Implementation

[0049] To better illustrate the purpose, technical solution, and advantages of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and specific embodiments.

[0050] Unless otherwise specified, all materials used in the embodiments and comparative examples are commercially available.

[0051] Example 1

[0052] An embodiment of the present invention describes a clustered ferric phosphate, its preparation method, and its application. The preparation method of the clustered ferric phosphate includes the following steps:

[0053] (1) A toluene solution of polyethylene glycol PEG10000 and a toluene solution of toluene-2,4-diisocyanate were mixed, and the resulting mixture was heated to 110°C and kept at that temperature for 6 hours to obtain a modified polyethylene glycol solution; the mass ratio of PEG10000 to toluene in the toluene solution of polyethylene glycol PEG10000 was 3:10, the mass ratio of toluene-2,4-diisocyanate to toluene in the toluene solution of toluene-2,4-diisocyanate was 3:10, and the molar ratio of PEG10000 to toluene-2,4-diisocyanate when the toluene solution of polyethylene glycol PEG10000 and the toluene solution of toluene-2,4-diisocyanate were mixed was 1:2.2;

[0054] (2) A toluene solution of p-phenylenediamine was added to the modified polyethylene glycol solution and mixed and reacted for 6 hours. Diethyl ether was added to the resulting mixture to cause a precipitation reaction. After the reaction was complete and no more precipitate was produced, the resulting mixture was filtered, washed with diethyl ether, and dried to obtain an intermediate solid product. The molar ratio of modified polyethylene glycol to p-phenylenediamine in the mixture was 1:3.

[0055] (3) The intermediate solid product was dissolved in chloroform, and the pH of the resulting solution was adjusted to 1.5 with sulfuric acid. Then, aniline monomer and initiator were added, and the resulting mixture was mixed and reacted under a nitrogen atmosphere for 9 h, while the reaction temperature was controlled at 0 °C. The resulting emulsion was filtered, washed with solid product, deionized water and ethanol in sequence, and dried under vacuum at 60 °C for 24 h to obtain a polyaniline block copolymer. The molar concentration of the aniline monomer after adding the mixture was 5 mol / L, and the mass ratio of the intermediate solid product to the aniline monomer was 5:6. The initiator was ferric chloride, which was prepared as a solution with ethanol before adding the mixture. The solid-liquid ratio of the solution was 3 g / 5 mL, and the molar ratio of ferric chloride to the aniline monomer was 4:1.

[0056] (4) The polyaniline block copolymer was added to water and the pH of the resulting mixture was adjusted to 2. Then, ferric chloride and ammonium hydrogen phosphate were added and stirred for 5 hours. The resulting mixture was filtered to obtain the solid product, washed and dried to obtain the ferric phosphate precursor. The ferric chloride was prepared in advance as a 1 mol / L aqueous solution and the ammonium hydrogen phosphate was prepared in advance as a 1 mol / L aqueous solution. The mass ratio of the polyaniline block copolymer to the ferric chloride was 1:4, and the molar ratio of iron in the ferric chloride to phosphorus in the ammonium hydrogen phosphate was 1:1.

[0057] (5) The iron phosphate precursor is heated to 700°C and kept at that temperature for 5 hours under a nitrogen atmosphere to obtain the clustered iron phosphate.

[0058] The clustered iron phosphate was observed under a scanning electron microscope, as follows: Figure 1 As shown, the product has a uniform morphology and exhibits a distinct clustered structure.

[0059] The product was mixed with lithium hydroxide, and the resulting mixture was then transferred to a grinder and ground for 2 hours using ethanol as a dispersant. The resulting slurry was dried at 60°C for 24 hours, and the resulting powder was transferred to a tube furnace and held at 700°C for 10 hours under a nitrogen atmosphere to obtain clustered lithium iron phosphate material. The molar ratio of iron in the clustered lithium iron phosphate to lithium in lithium hydroxide was 1:1.

[0060] Example 2

[0061] An embodiment of the present invention describes a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is only that the mass ratio of the polyaniline block copolymer to ferric chloride in step (4) is 1:5.

[0062] Example 3

[0063] An embodiment of the present invention describes a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is only that the mass ratio of the polyaniline block copolymer to ferric chloride in step (4) is 1:3.

[0064] Example 4

[0065] An embodiment of the present invention describes a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is only that the mass ratio of the polyaniline block copolymer to ferric chloride in step (4) is 1:6.

[0066] Example 5

[0067] An embodiment of the present invention describes a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is only that the mass ratio of the polyaniline block copolymer to ferric chloride in step (4) is 1:2.

[0068] Example 6

[0069] This invention relates to an embodiment of a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is that the PEG10000 is replaced with an equimolar amount of PEG12000.

[0070] Example 7

[0071] This invention provides an embodiment of a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is that the PEG10000 is replaced with an equimolar amount of PEG6000.

[0072] Example 8

[0073] This invention provides an embodiment of a clustered ferric phosphate, its preparation method, and its application. The difference between the preparation method of the clustered ferric phosphate and that of Example 1 is that the PEG10000 is replaced with an equimolar amount of PEG20000.

[0074] Comparative Example 1

[0075] A method for preparing anhydrous iron phosphate and lithium iron phosphate materials includes the following steps:

[0076] (1) The pH of the solution was maintained at 1.8 with nitric acid and ammonia. Ferric chloride was added and stirred until it was completely dissolved to a molar concentration of 1 mol / L. Then, hexadecyltrimethylammonium bromide was added to the resulting solution at a molar ratio of 1:0.02. Ammonium hydrogen phosphate was then added. The resulting mixture was stirred and reacted for 5 h. After filtration, washing and drying, the resulting mixture was used to obtain the ferric phosphate precursor. Then, it was kept at 700 °C for 5 h under a nitrogen atmosphere to obtain anhydrous ferric phosphate. The molar ratio of iron in the ferric chloride to phosphorus in the ammonium hydrogen phosphate was 1:1.

[0077] (2) The anhydrous iron phosphate and lithium hydroxide are mixed, and the resulting mixture is then transferred to a grinder with ethanol as a dispersant and ground for 2 hours. The resulting slurry is dried at 60°C for 24 hours, and the resulting powder is transferred to a tube furnace and kept at 700°C for 10 hours under a nitrogen atmosphere to obtain lithium iron phosphate material; wherein the molar ratio of iron in anhydrous iron phosphate to lithium in lithium hydroxide is 1:1.

[0078] Comparative Example 2

[0079] A method for preparing iron phosphate and lithium iron phosphate materials includes the following steps:

[0080] (1) The pH of the solution was maintained at 1.8 with nitric acid and ammonia. Ferric chloride was added and stirred until completely dissolved to a molar concentration of 1 mol / L. Then, hexadecyltrimethylammonium bromide was added to the resulting solution at a molar ratio of 1:0.02. Then, hydrogen phosphate, PEG10000 and aniline monomer were added. The resulting mixture was stirred and reacted for 5 h. After filtration, washing and drying, the resulting mixture was used to obtain the ferric phosphate precursor. Then, it was kept at 700℃ for 5 h under a nitrogen atmosphere to obtain ferric phosphate. The molar ratio of iron in the ferric chloride to phosphorus in the hydrogen phosphate was 1:1. The molar ratio of aniline monomer to iron in ferric chloride was 1:7. The mass ratio of PEG10000 to aniline monomer was 1:1.

[0081] (2) The iron phosphate and lithium hydroxide are mixed, and the resulting mixture is then transferred to a grinder with ethanol as a dispersant and ground for 2 hours. The resulting slurry is dried at 60°C for 24 hours, and the resulting powder is transferred to a tube furnace and kept at 700°C for 10 hours under a nitrogen atmosphere to obtain lithium iron phosphate material; wherein the molar ratio of iron in iron phosphate to lithium in lithium hydroxide is 1:1.

[0082] Example of effect 1

[0083] To verify the effectiveness of the product described in this invention, the lithium iron phosphate materials prepared in each embodiment and comparative example were used as positive electrode sheets for coin-type lithium-ion batteries. The preparation method was as follows: each lithium iron phosphate material was mixed with binder PVDF and conductive agent acetylene black in a mass ratio of 8:1:1, and a slurry was prepared using N-methylpyrrolidone as a dispersant and coated on aluminum foil. After vacuum drying, it was stamped into a circular positive electrode sheet.

[0084] Subsequently, the electrode was assembled into a coin cell in a glove box using a lithium sheet as the counter electrode, Celgard 2400 PE as the separator, and 1 mol / L LiPF6 as the electrolyte.

[0085] The obtained button cells were subjected to rate performance testing and low-temperature performance testing at voltages ranging from 2.5 to 4.2V.

[0086] (1) Rate performance test: The cells were charged and discharged 5 times at 0.1C, 0.2C, 1C, 2C, 5C and 10C respectively. The discharge specific capacity of the first discharge and the discharge specific capacity of the last cycle at different rates were statistically analyzed.

[0087] (2) Low temperature performance: The battery was fully charged after two charge-discharge cycles at 0.2C rate at room temperature. The battery was placed in a -20℃ low temperature test chamber for 10 hours, and then discharged at 0.2C rate. The discharge specific capacity was calculated.

[0088] The test results are shown in Table 1.

[0089] Table 1

[0090]

[0091]

[0092] As shown in Table 1, the clustered lithium iron phosphate products prepared in the various embodiments of the present invention exhibit very ideal conventional electrochemical performance. At a rate of 0.1C, the discharge specific capacity of each product can reach over 160 mAh / g, and even at a rate of 10C, the products still maintain a discharge specific capacity of over 120 mAh / g. On the other hand, when subjected to a low temperature environment of -20℃, the products of each embodiment can achieve a discharge specific capacity of at least 98 mAh / g at a rate of 0.2C. In contrast, the lithium iron phosphate material obtained by Comparative Example 1, which is prepared by conventional processes using iron phosphate, has poor electrochemical performance in both conventional and low-temperature environments due to the lack of a special morphological structure. While Comparative Example 2 further introduced aniline monomers for coating during the preparation of iron phosphate based on the process of Comparative Example 1, the overall performance of the product was improved to some extent, but it was still far inferior to the products of the various embodiments. In Examples 1-5, the ratio of iron source to polyaniline block copolymer introduced during the preparation of clustered ferric phosphate was not the same. When the amount of polyaniline block copolymer was too small, the product not only failed to construct the optimal clustered system, but also had a smaller proportion of conductive layer formed after calcination. Therefore, the discharge specific capacity and rate performance of the product were poor. However, if too much polyaniline block copolymer was introduced, the relative actual capacity of the product decreased, but the rate performance of the product did not improve further; instead, it decreased to some extent. This may be because excessive polyaniline block copolymer caused some material to agglomerate during the precipitation of the ferric phosphate precursor, resulting in an uneven morphology of the final product and thus weakening the rate performance. The performance comparison of the products in Examples 1, 7, and 8 shows that when using polyethylene glycol to prepare modified polyethylene glycol and subsequently used to prepare intermediate solid products, the molecular weight (molecular length) of polyethylene glycol also has a certain impact on the product performance. Polyethylene glycol with a moderate molecular weight yields the best results.

[0093] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this article and are not intended to limit the scope of protection of this article. Although this application has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this article without departing from the essence and scope of the technical solutions of this article.

Claims

1. A method for preparing clustered iron phosphate, characterized in that, Includes the following steps: A toluene solution of polyethylene glycol and a toluene solution of diisocyanate are mixed, and the resulting mixture is heated to 100-120°C and kept at that temperature for 5-6 hours to obtain a modified polyethylene glycol solution. A p-phenylenediamine solution was added to the modified polyethylene glycol solution and mixed and reacted for 5-6 hours. Diethyl ether was added to the resulting mixture to cause a precipitation reaction. After the reaction was complete, the resulting mixture was filtered, washed and dried to obtain an intermediate solid product. The intermediate solid product was dissolved in an organic solvent. After adjusting the pH of the resulting solution to 1-2, aniline monomer and initiator were added. The resulting mixture was mixed and reacted under a protective atmosphere for 8-10 hours, while the reaction temperature was controlled at 0-5℃. The resulting emulsion was filtered to obtain a solid product, washed, and dried to obtain a polyaniline block copolymer. The polyaniline block copolymer was added to water and the pH of the resulting mixture was adjusted to 1.6-2.

2. Then, an iron source and a phosphoric acid source were added and reacted for 2-6 hours. The resulting mixture was filtered to obtain a solid product, washed, and dried to obtain an iron phosphate precursor. The iron phosphate precursor is heated to 500-700°C under a protective atmosphere and held for 4-10 hours to obtain the clustered iron phosphate.

2. The method for preparing clustered iron phosphate as described in claim 1, characterized in that, The average molecular weight of the polyethylene glycol is 5000~25000.

3. The method for preparing clustered iron phosphate as described in claim 1, characterized in that, The molar ratio of polyethylene glycol to diisocyanate is 1:(2~2.5); the diisocyanate is at least one of methylene diphenyl diisocyanate, toluene diisocyanate, hexamethylene diisocyanate, and methylene dicyclohexyl diisocyanate.

4. The method for preparing clustered iron phosphate as described in claim 1, characterized in that, The molar ratio of modified polyethylene glycol in the modified polyethylene glycol solution to p-phenylenediamine in the p-phenylenediamine solution is 1:(2~3).

5. The method for preparing clustered iron phosphate as described in claim 1, characterized in that, The mass ratio of the intermediate solid product to the aniline monomer is (2.2~7):

6.

6. The method for preparing clustered iron phosphate as described in claim 1, characterized in that, The iron source is at least one of ferric nitrate and ferric chloride; the mass ratio of the polyaniline block copolymer to the iron source is 1:(3~5).

7. Clustered ferric phosphate prepared by the method for preparing clustered ferric phosphate according to any one of claims 1 to 6.

8. A clustered lithium iron phosphate material, characterized in that, It is prepared from the clustered iron phosphate as described in claim 7.

9. A method for preparing the clustered lithium iron phosphate according to claim 8, characterized in that, Includes the following steps: Clustered iron phosphate and lithium source are mixed and ground. The resulting mixture is heated to 600~850℃ and held for 6~15h under a protective atmosphere to obtain the clustered lithium iron phosphate material.

10. A lithium-ion battery, characterized in that, It includes a positive electrode sheet, wherein the positive electrode sheet comprises the clustered lithium iron phosphate material of claim 8.

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