Preparation method of iron phosphate with high iron-phosphorus ratio
By preparing and treating iron and phosphorus source solutions, combined with the use of inorganic acids and ferrous sulfate, the iron-phosphorus ratio of iron phosphate was successfully improved, and the problems of insufficient iron-phosphorus ratio and degradation of performance after the addition of titanium elements in the prior art were solved, thereby achieving efficient and stable high-performance iron phosphate preparation.
Patent Information
- Application Number
- CN202411924164.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-12-25
- Publication Date
- 2025-03-28
AI Technical Summary
It is difficult to prepare iron phosphate with an iron-phosphorus ratio of more than 0.96 in the prior art, and the iron-phosphorus ratio will usually be reduced after the addition of titanium elements, making it difficult to meet the needs of high-performance iron-phosphorus positive electrode materials.
By preparing iron and phosphorus source solutions, adjusting the pH value and mixing them respectively, the inorganic acid and ferrous sulfate solution are added, the heat is raised and insulated, and hydrogen peroxide is added for oxidation. Finally, anhydrous iron phosphate with an iron-phosphorus ratio of no less than 0.965 is obtained by filtration, washing and calcination.
The preparation of iron phosphate with high-iron-phosphorus ratio is achieved, taking into account electrical properties and stability, and the process is simplified, production efficiency is improved, and the problems of uneven reactions and low product purity are avoided.
Smart Images
Figure CN119706770A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of lithium-ion battery materials, and in particular to a method for preparing high iron-to-phosphorus ratio iron phosphate. Background Art
[0002] With the continuous advancement of lithium-ion battery technology, the preparation of high-performance lithium iron phosphate cathode materials has increasingly stringent requirements on the performance of the precursor iron phosphate. In order to obtain high-capacity batteries, certain lithium iron phosphate cathode materials with special properties require their precursor iron phosphate to have the characteristics of a high iron-to-phosphorus ratio (i.e., a high molar ratio of iron to phosphorus). However, the iron phosphate prepared by the current conventional industrial production method generally has an iron-to-phosphorus ratio lower than 0.96, and some are even lower than 0.945. Such performance indicators are difficult to meet the market demand for high-performance iron phosphate cathode materials.
[0003] On the other hand, in order to improve the performance of lithium iron phosphate batteries, technicians often add titanium to the raw materials for preparing iron phosphate. However, this operation often further reduces the iron-phosphorus ratio of iron phosphate.
[0004] Based on this, a method for preparing industrial-grade high iron-to-phosphorus ratio ferric phosphate is needed. Summary of the invention
[0005] In order to solve the above technical problems, the present invention provides a method for preparing high iron-phosphorus ratio ferric phosphate, comprising the following steps: Figure 1 As shown: S1. Prepare an iron source solution, wherein the pH value of the iron source solution is 1.3-3; the iron source solution is a ferrous salt solution or a mixture of a ferrous salt solution and a titanyl sulfate solution; S2, preparing a phosphorus source solution, mixing a phosphate salt, an ammonia solution and a hydrogen peroxide solution to obtain a phosphorus source solution; the pH value of the phosphorus source solution is 6 to 8.6; S3, the iron source solution and the phosphorus source solution are flowed into a reactor to react for 0.5 to 3 hours, and then stirred and slurried to obtain iron phosphate slurry; S4, mixing the ferric phosphate slurry and the inorganic acid solution for 0.5 to 2.5 hours to obtain a mixed solution; S5, adding ferrous sulfate solution to the mixed solution, heating to 85-95° C., and keeping warm for 0.5-3 h to obtain a white mixed slurry; S6, adding hydrogen peroxide to the white mixed slurry to oxidize the white mixed slurry until there is no ferrous ion, thereby obtaining a mixed slurry; S7. The mixed slurry is filtered and washed until the conductivity is 500-4000 μs / cm, and calcined to obtain anhydrous ferric phosphate, i.e., finished ferric phosphate; the iron-phosphorus ratio of the anhydrous ferric phosphate is not less than 0.965.
[0006] Moreover, in the step S1, the ferrous salt solution is ferrous sulfate or ferrous chloride.
[0007] Moreover, in the step S1, the concentration of the iron source solution is 0.6-2 mol / L.
[0008] Moreover, in the step S2, the phosphate salt is at least one of industrial grade sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, or agricultural grade monoammonium phosphate; The concentration of the phosphorus source solution is 0.6-2 mol / L.
[0009] Moreover, in the step S3, the temperature of the iron phosphate slurry is 45-69°C; The molar ratio of the phosphorus element in the phosphorus source solution to the iron element in the iron source solution is 0.8 to 1.15.
[0010] Moreover, in step S4, the inorganic acid is sulfuric acid, phosphoric acid or nitric acid.
[0011] Moreover, in the step S5, the heating rate is 1°C / 0.5min to 1°C / 2min; The molar ratio of iron in the ferrous sulfate solution to iron in the mixed solution is 0.02 to 0.2; The ferrous sulfate solution is added by direct pouring.
[0012] Moreover, in step S6, the mass of the hydrogen peroxide is 0.04 of the mixed slurry; the standard of being free of ferrous ions is that the mixed slurry no longer changes color when tested with potassium ferrocyanide.
[0013] Furthermore, in the step S7, the calcination temperature is 500-620°C.
[0014] Furthermore, the mass of the titanyl sulfate solution is such that the titanium content in the anhydrous iron phosphate is 800 to 5000 ppm.
[0015] On the other hand, the present invention provides iron phosphate prepared by a method for preparing iron phosphate with a high iron-to-phosphorus ratio.
[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The present invention comprises the following steps: mixing ferric phosphate slurry and an inorganic acid solution to obtain a mixed solution; adding a ferrous sulfate solution to the mixed solution, heating the mixture to a reaction temperature, and maintaining the mixture at the reaction temperature until the mixed solution turns white; adding hydrogen peroxide to oxidize the whitened mixed solution to be free of ferrous ions to obtain a mixed slurry, and heating the mixed slurry to a heat preservation temperature; after heat preservation for a certain period of time, filtering, washing, and calcining the mixed slurry to obtain anhydrous ferric phosphate having an iron-phosphorus ratio of not less than 0.965.
[0017] 2. The present invention increases the iron content of the slurry by adding ferrous sulfate solution to the ferrous phosphate slurry, and converts Fe 2+ Oxidized to Fe 3+ , Fe 3+ Rapidly and free PO4 in the slurry 3- The reaction generates iron phosphate. Due to the high slurry temperature, the nucleation rate and growth rate are accelerated, and the degree of crystallization is high, which can effectively improve the iron-phosphorus ratio of the prepared iron phosphate.
[0018] 3. Although the addition of titanium usually reduces the iron-phosphorus ratio of iron phosphate, the present invention optimizes the preparation process so that while introducing titanium into iron phosphate, a relatively high iron-phosphorus ratio can be maintained, thereby taking into account both the electrical properties and stability of iron phosphate.
[0019] 4. The preparation method of the present invention has a simple process, convenient operation, and close connection between the steps, which effectively avoids the problems of uneven reaction and low product purity that may occur in traditional preparation methods, and improves production efficiency. BRIEF DESCRIPTION OF THE DRAWINGS
[0020] In order to more clearly illustrate the embodiments of this specification or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this specification. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.
[0021] Figure 1 A schematic flow chart of a method for preparing high iron-phosphorus ratio ferric phosphate provided by the present invention; Figure 2 Schematic diagram of the process of Example 1; Figure 3 This is a SEM image of the iron phosphate provided in Example 1 at a magnification of 5000; Figure 4 This is a SEM image of the iron phosphate provided in Comparative Example 1 at a magnification of 5000. DETAILED DESCRIPTION
[0022] Example 1 S1. Prepare an iron salt solution: add deionized water to a ferrous sulfate solution having a concentration of 1.2 mol / L, and adjust the pH to 1.5 with sulfuric acid to obtain a ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.2 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4, add water to the yellow slurry to dilute it to a concentration of 0.6 mol / L, add 0.6 ratio of phosphoric acid and 0.02 ratio of ferrous sulfate, heat the slurry, set the heating program to heat it to 95°C for 90 minutes, when it reaches a certain temperature and the yellow slurry turns white, add 0.04 ratio of hydrogen peroxide to Fe 2+ Completely oxidized to Fe 3+ After testing the absence of ferrous iron with potassium ferrocyanide, the mixture was kept warm for 1 hour, and then the slurry was taken out, filtered, washed, and the conductivity was washed to 500 μs / cm. The sintering was performed at 580°C / 4h to obtain the anhydrous ferric phosphate.
[0023] Example 2 Compared with Example 1, this example increases the solubility of the iron source and phosphorus source (ie, ferrous sulfate and diammonium hydrogen phosphate), and also dilutes the concentration of the mixed slurry.
[0024] S1. Prepare an iron salt solution: add deionized water to a ferrous sulfate solution having a concentration of 1.7 mol / L, and adjust the pH to 1.5 with sulfuric acid to obtain a ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.7 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4, add water to the yellow slurry to dilute it to a concentration of 1 mol / L, add 0.8 ratio of phosphoric acid and 0.02 ratio of ferrous sulfate, heat the slurry, set the heating program to heat it to 95°C for 90 minutes, when it reaches a certain temperature and the yellow-white slurry turns into white-pink, add 0.04 ratio of hydrogen peroxide to Fe 2+ Completely oxidized to Fe 3+ After testing the absence of ferrous iron using potassium ferrocyanide, the mixture was kept warm for 1 hour, and then the slurry was taken out and washed, and the conductivity was washed to 500 μs / cm. The slurry was sintered at 580°C for 4 hours to obtain the anhydrous ferric phosphate.
[0025] Example 3 The difference between this embodiment and embodiment 1 is that the iron source is doped with titanyl sulfate, that is, the iron source solution is a mixture of a ferrous salt solution and a titanyl sulfate solution, as follows: S1. Prepare an iron salt solution: add ferrous sulfate solution to deionized water to prepare a ferrous sulfate solution with a concentration of 1.2 mol / L, dissolve 5 g of titanyl sulfate in 500 ml of water and add the solution thereto, adjust the pH to 1.5 with sulfuric acid, and obtain ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.2 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4, add water to the yellow slurry to dilute it to a concentration of 0.6 mol / L, add 0.6 ratio of phosphoric acid and 0.02 ratio of ferrous sulfate, heat the slurry, set the heating program to heat it to 95°C for 90 minutes, when it reaches a certain temperature and the yellow-white slurry turns into white-pink, add 0.04 ratio of hydrogen peroxide to Fe 2+ Completely oxidized to Fe 3+ After using potassium ferrocyanide to test the absence of ferrous ions, keep warm for 1 hour, then take out the slurry, wash it, wash the conductivity to 500μs / cm, and sinter it at 580℃ / 4h to obtain the anhydrous ferric phosphate.
[0026] Example 4 The difference between this embodiment and embodiment 2 is that the iron source is doped with titanyl sulfate, that is, the iron source solution is a mixture of a ferrous salt solution and a titanyl sulfate solution, as follows: S1. Prepare an iron salt solution: add ferrous sulfate solution to deionized water to prepare a ferrous sulfate solution with a concentration of 1.7 mol / L, dissolve 5 g of titanyl sulfate in 500 ml of water and add the solution thereto, adjust the pH to 1.5 with sulfuric acid, and obtain ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.7 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4. Add water to the yellow slurry to make a slurry and dilute it to a concentration of 1 mol / L. Add 0.8 ratio of phosphoric acid and 0.1 ratio of ferrous sulfate, heat the slurry, set the heating program to heat it to 95°C for 90 minutes, and when the yellow-white slurry turns into white-pink when heated to a certain temperature, add 0.04 ratio of hydrogen peroxide to completely oxidize Fe2+ to Fe3+. After testing the absence of ferrous iron with potassium ferrocyanide, keep it warm for 1 hour, then take out the slurry, wash it, wash the conductivity to 500μs / cm, and sinter it at 580°C / 4h to obtain the anhydrous iron phosphate.
[0027] Comparative Example 1 The difference between this embodiment and embodiment 1 is that in step S4, no ferrous sulfate solution and hydrogen peroxide are added, specifically as follows: S1. Prepare an iron salt solution: add deionized water to a ferrous sulfate solution containing titanium dioxide to prepare a ferrous sulfate solution with a concentration of 1.2 mol / L, and adjust the pH to 1.5 with sulfuric acid to obtain a ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.2 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4. Add water to the yellow slurry to dilute it to a concentration of 0.6 mol / L, add 0.6 ratio of phosphoric acid, heat the slurry, set the heating program to heat to 95°C for 90 minutes, keep warm for 1 hour, then take out the slurry, wash it, wash the conductivity to 500 μs / cm, and sinter it at 580°C / 4h to obtain the anhydrous iron phosphate.
[0028] Comparative Example 2 The difference between this embodiment and embodiment 2 is that in step S4, no ferrous sulfate solution and hydrogen peroxide are added, specifically as follows: S1. Prepare an iron salt solution: add deionized water to a ferrous sulfate solution containing titanium dioxide to prepare a ferrous sulfate solution with a concentration of 1.7 mol / L, and adjust the pH to 1.5 with sulfuric acid to obtain a ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.7 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4. Add water to the yellow slurry to dilute it to a concentration of 1 mol / L, add 0.8 ratio of phosphoric acid, heat the slurry, set the heating program to heat to 95°C for 90 minutes, keep warm for 1 hour, then take out the slurry, wash it, wash the conductivity to 500 μs / cm, and sinter it at 580°C / 4h to obtain the anhydrous iron phosphate.
[0029] Comparative Example 3 The difference between this embodiment and embodiment 3 is that in step S4, no ferrous sulfate solution and hydrogen peroxide are added, specifically as follows: S1. Prepare an iron salt solution: add deionized water to a ferrous sulfate solution containing titanium dioxide to prepare a ferrous sulfate solution with a concentration of 1.2 mol / L, dissolve 5 g of titanyl sulfate in 500 ml of water and add the solution thereto, adjust the pH to 1.5 with sulfuric acid, and obtain a ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.2 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously flowed into the reactor for 60 minutes, and after potassium ferrocyanide is used to test the absence of ferrous ions, the slurry is filtered and washed to obtain a yellow slurry; S4. Add water to the yellow slurry to dilute it to a concentration of 0.6 mol / L, add 0.6 ratio of phosphoric acid, heat the slurry, set the heating program to heat to 95°C for 90 minutes, keep warm for 1 hour, then take out the slurry, wash it, wash the conductivity to 500 μs / cm, and sinter it at 580°C / 4h to obtain the anhydrous iron phosphate.
[0030] Comparative Example 4 The difference between this embodiment and embodiment 4 is that in step S4, no ferrous sulfate solution and hydrogen peroxide are added, specifically as follows: S1. Prepare an iron salt solution: add deionized water to a ferrous sulfate solution containing titanium dioxide to prepare a ferrous sulfate solution with a concentration of 1.7 mol / L, dissolve 5 g of titanyl sulfate in 500 ml of water and add the solution thereto, adjust the pH to 1.5 with sulfuric acid, and obtain a ferrous sulfate solution A1; S2. Prepare a mixed solution of phosphate and ammonia water: weigh monoammonium phosphate and add deionized water to prepare a diammonium hydrogen phosphate solution with a concentration of 1.7 mol / L, add ammonia water to adjust the pH to 7.0, add 0.65 ratio of hydrogen peroxide, and stir evenly; S3, the prepared iron salt and phosphate salt are simultaneously fed into the reactor to react for 60 minutes, and after testing with potassium ferrocyanide to find out that there is no ferrous ion, the slurry is filtered and washed to obtain a yellow slurry; S4. Add water to the yellow slurry to dilute it to a concentration of 0.6 mol / L, add 0.6 ratio of phosphoric acid, heat the slurry, set the heating program to heat to 95°C for 90 minutes, keep warm for 1 hour, then take out the slurry, wash it, wash the conductivity to 500 μs / cm, and sinter it at 580°C / 4h to obtain the anhydrous iron phosphate.
[0031] Experimental Section
[0032] Experiment 1 The physical and chemical properties of the iron phosphate obtained in Examples 1-4 and Comparative Examples 1-4 were measured, and the results are shown in Table 1 below.
[0033] Table 1 Physical and chemical data results of iron phosphate of Examples 1-4 and Comparative Examples 1-4
[0034] As can be seen from Table 1, the iron-phosphorus ratios of the finished ferric phosphate products prepared in Examples 1-4 are relatively high, ranging from 0.965 to 0.975, with the highest being Example 1, which has an iron-phosphorus ratio of 0.975; while in the comparative examples, no ferrous sulfate solution and hydrogen peroxide were added, and the obtained iron phosphate phosphorus ratios were basically below 0.96 (0.947-0.958).
[0035] In addition, from the comparison between Comparative Example 3 and Example 3 (doped with titanium element), and the comparison between Comparative Example 4 and Example 4 (doped with titanium element), it can be seen that after the addition of titanium element (doping usually reduces the iron-phosphorus ratio, for example, Examples 3 and 4 have lower iron-phosphorus ratios than Examples 1 and 2), the scheme of the present application can still effectively improve the iron-phosphorus ratio, and the iron-phosphorus ratio of Comparative Examples 3 and 4 is increased from about 0.950 to more than 0.963 of Examples 3 and 4; in the subsequent electrical performance test of lithium iron phosphate batteries, it was confirmed that the electrical performance of lithium iron phosphate batteries prepared using Examples 3 and 4 as precursors was improved.
[0036] At the same time, all samples in the embodiments and comparative examples have BET values of about 7-10, and the sulfur content is relatively low, but the sulfur content in the embodiments is at a lower level than that in the comparative example; a higher sulfur content will affect the formation of spherical particles in the later preparation process of lithium iron phosphate, resulting in agglomeration of small lithium iron phosphate particles, and the agglomeration phenomenon will increase the internal resistance of the material, causing the discharge capacity and cycle performance of the lithium iron phosphate battery to decrease significantly, and the sulfur impurities in iron phosphate may increase the charge transfer impedance of the battery, affecting the charge and discharge rate and efficiency of the battery.
[0037] Experiment 2 The iron phosphate prepared in Example 1 and Comparative Example 1 was scanned by electron microscope. The results are as follows: Figure 3-4 As shown, Figure 3 The SEM image of the iron phosphate provided in Example 1 at 5000 times magnification is as follows: Figure 4 The SEM image of the iron phosphate provided in Comparative Example 1 at 5000 times magnification shows that: Figure 3 The primary particles of Example 1 are relatively large, with obvious single crystals and high iron and phosphorus content. Figure 4 The primary particles of Comparative Example 1 are smaller, so the iron-phosphorus ratio is lower.
Claims
1. A method for preparing ferric phosphate with a high iron-to-phosphorus ratio, characterized in that: The steps include: S1. Prepare an iron source solution, wherein the pH value of the iron source solution is 1.3-3; the iron source solution is a ferrous salt solution or a mixture of a ferrous salt solution and a titanyl sulfate solution; S2, preparing a phosphorus source solution, mixing a phosphate salt, an ammonia solution and a hydrogen peroxide solution to obtain a phosphorus source solution; the pH value of the phosphorus source solution is 6 to 8.6; S3, the iron source solution and the phosphorus source solution are flowed into a reactor to react for 0.5 to 3 hours, and then stirred and slurried to obtain iron phosphate slurry; S4, mixing the ferric phosphate slurry and the inorganic acid solution for 0.5 to 2.5 hours to obtain a mixed solution; S5, adding ferrous sulfate solution to the mixed solution, heating to 85-95° C., and keeping warm for 0.5-3 h to obtain a white mixed slurry; S6, adding hydrogen peroxide to the white mixed slurry to oxidize the white mixed slurry until there is no ferrous ion, thereby obtaining a mixed slurry; S7, filter-pressing the mixed slurry, washing it until the conductivity is 500-4000 μs / cm, and calcining it to obtain anhydrous iron phosphate.
2. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In step S1, the ferrous salt solution is ferrous sulfate or ferrous chloride; The concentration of the iron source solution is 0.6-2 mol / L.
3. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In the step S2, the phosphate salt is at least one of industrial grade sodium phosphate, sodium dihydrogen phosphate, disodium hydrogen phosphate, potassium phosphate, ammonium phosphate, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, or agricultural grade monoammonium phosphate; The concentration of the phosphorus source solution is 0.6-2 mol / L.
4. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In step S3, the temperature of the iron phosphate slurry is 45-69° C.; The molar ratio of the phosphorus element in the phosphorus source solution to the iron element in the iron source solution is 0.8 to 1.
15.
5. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In step S4, the inorganic acid is sulfuric acid, phosphoric acid or nitric acid.
6. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In step S5, the heating rate is 1°C / 0.5min to 1°C / 2min; The molar ratio of the iron in the ferrous sulfate solution to the iron in the mixed solution is 0.02 to 0.2; The ferrous sulfate solution is added by direct pouring.
7. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In step S6, the mass of the hydrogen peroxide is 0.04 of the mixed slurry; the standard of being free of ferrous ions is that the mixed slurry no longer changes color when tested with potassium ferrocyanide.
8. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: In the step S7, the calcination temperature is 500-620°C.
9. The method for preparing high iron-to-phosphorus ratio ferric phosphate according to claim 1, characterized in that: The mass of the titanyl sulfate solution is such that the titanium content in the anhydrous ferric phosphate is 800 to 5000 ppm.
10. Ferric phosphate prepared by the method for preparing ferric phosphate with a high iron to phosphorus ratio as claimed in any one of claims 1 to 9.