Monocrystal-like dense iron phosphate material and preparation method thereof

Abstract

The invention provides a single-crystal-like dense iron phosphate material and a preparation method thereof.The iron phosphate material is prepared through the following steps that S1, a certain amount of pure water is added into a reaction kettle for bottoming, a ferrite solution and a phosphorus salt solution are added at the temperature of 30-60 DEG C, and ferrous phosphate slurry A is obtained; s2, carrying out solid-liquid separation and washing treatment on the ferrous phosphate slurry A to obtain a ferrous phosphate filter cake; s3, pulping the ferrous phosphate filter cake with pure water, uniformly stirring, transferring into a reaction kettle, continuously stirring, heating, mixing a phosphoric acid solution and a hydrogen peroxide solution, and adding to obtain white slurry B; and S4, carrying out solid-liquid separation, washing treatment and flash evaporation drying on the white slurry B to obtain iron phosphate dihydrate, and calcining the iron phosphate dihydrate to obtain the monocrystal-like dense iron phosphate material with the high iron-phosphorus ratio. When the iron phosphate provided by the invention is matched with conventional iron phosphate to prepare lithium iron phosphate, the quantity ratio of small-particle lithium iron phosphate can be effectively controlled.

Description

Technical Field

[0001] The present invention relates to the technical field of batteries, and in particular to a single-crystal-like dense iron phosphate material and a preparation method thereof. Background Art

[0002] In the process of preparing lithium iron phosphate by high-temperature solid-phase method using iron phosphate as a precursor, in order to effectively improve the compaction density of lithium iron phosphate, a commonly used technical means is to use two iron phosphates with different morphologies or different physical and chemical properties as precursors, in order to prepare lithium iron phosphate materials with large and small particle sizes.

[0003] For example, the patent "Method for preparing high energy density lithium iron phosphate, CN 116835559 A" prepares iron phosphate with spherical morphology and flake morphology respectively, mixes them in proportion and grinds them. Due to the different grinding efficiencies of flake iron phosphate and spherical iron phosphate, the grinding stage will produce a slurry with a wide particle size distribution and both large and small particle sizes. After processes such as spray drying and sintering, lithium iron phosphate with large and small particle sizes can be obtained.

[0004] The patent "A method for preparing iron phosphate for high-purity and high-compacted lithium iron phosphate, CN 109775679 A" prepares two types of iron phosphate with different particle size distributions, mixes them in proportion, and then prepares lithium iron phosphate with different particle size distributions.

[0005] Patent "A method for preparing high-compacted lithium iron phosphate, CN 111392705 B" mixes iron phosphate with a high iron-phosphorus ratio (0.980-0.985) and a low iron-phosphorus ratio (0.965-0.970), grinds out two slurries with D50=1200-1300 nm and D50=450-550nm, and after mixing, forms a slurry with a wide particle size distribution and both large and small particle sizes, and obtains lithium iron phosphate with large and small particle sizes through processes such as spray drying and sintering.

[0006] The above-mentioned prior art solutions are to mix two different iron phosphate materials, and form a slurry with large and small particle gradations during grinding, in order to prepare lithium iron phosphate with large and small particle gradations. However, on the one hand, since the particle size of the slurry produced by grinding conforms to the normal distribution, it is actually difficult to effectively control the ratio of large-sized particles and small-sized particles in the slurry. Even according to the solution provided by the patent "A method for preparing high-pressure compacted lithium iron phosphate, CN 111392705 B" - first grind out slurries of different D50 particle sizes separately, and then mix them, the size grading effect of the obtained mixed slurry is also limited, because the particle size distribution of large particle slurry and small particle slurry conforms to the normal distribution, and the particle size of the mixed slurry will still retain the characteristics of the normal distribution to a large extent. On the other hand, since the small particles in the slurry may agglomerate and grow into large particles during the subsequent sintering process, the proportion of small particles in the finished lithium iron phosphate product will be less than the proportion of small particles in the slurry, and the grading characteristics of large and small particles cannot be effectively inherited. Therefore, the existing technical solutions have the disadvantages that the number of large-sized and small-sized lithium iron phosphate particles is difficult to accurately control and the compaction and lifting effect is limited. Summary of the invention

[0007] The present invention provides a single crystal dense iron phosphate material and a preparation method thereof. By using it in combination with conventional iron phosphate, a lithium iron phosphate material with large and small particle grading characteristics can be prepared, and the effective control of the proportion of large and small particles of lithium iron phosphate can be achieved, so as to solve the disadvantage that the proportion of large and small particles in the existing technical solution of mixing two kinds of iron phosphate to prepare large and small particle grading lithium iron phosphate is difficult to effectively control, and the details are as follows: S1. Prepare 0.5-1.5 mol / L phosphate solution and 0.5-1.5 mol / L ferrous salt solution respectively, add a certain amount of pure water into the reactor as the base, add the ferrous salt solution and the phosphate solution at 30-60°C, the feeding time is 0.5-3 h, react for 1-3 h after the feeding is completed, and obtain ferrous phosphate slurry A; S2, subjecting the ferrous phosphate slurry A obtained in step S1 to solid-liquid separation and washing to obtain a ferrous phosphate filter cake; S3, prepare 40-85wt% phosphoric acid solution and 10-25wt% hydrogen peroxide solution respectively, slurry the ferrous phosphate filter cake obtained in step S2 with pure water, stir evenly and transfer into a reactor, continue stirring and heat to 80-100°C, mix the phosphoric acid solution and the hydrogen peroxide solution and add, keep warm and react for 0.5-3 h, and obtain white slurry B; S4. The slurry B obtained in step S3 is subjected to solid-liquid separation, washing treatment, and flash drying to obtain ferric phosphate dihydrate. The ferric phosphate dihydrate is subjected to calcination treatment to obtain the single-crystal-like high iron-phosphorus ratio dense ferric phosphate material.

[0008] Furthermore, the phosphate solution in step S1 is prepared from any one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

[0009] Furthermore, the ferrous salt solution is prepared from any one of ferrous sulfate, ferrous nitrate, ferrous chloride, iron powder, and iron sheet.

[0010] Furthermore, the molar ratio of iron to phosphorus in the ferrous salt solution and the phosphate salt solution is controlled to be 1:0.9-1:1.2.

[0011] Furthermore, in step S3, the molar ratio of the phosphorus element after the phosphoric acid solution and the hydrogen peroxide solution are mixed to the iron element in the ferrous phosphate slurry A obtained in step S1 is n(P):n(Fe)=0.10-0.80:1.

[0012] Furthermore, in step S3, the phosphoric acid solution and the hydrogen peroxide solution are mixed and added within 30-90 minutes.

[0013] Furthermore, the primary particle size of the single-crystal-like dense iron phosphate material is 1-10 μm.

[0014] There is no obvious agglomeration between the primary particles of the iron phosphate material. The iron-phosphorus ratio of the single-crystal dense iron phosphate material is 0.975-0.985, the iron content is 36.5-37.5%, the phosphorus content is 20.55-20.75%, and the specific surface area is 1-4 m2 / g.

[0015] The iron phosphate material provided by the present invention is used in combination with conventional iron phosphate to prepare a high-density lithium iron phosphate material with large and small particle grading characteristics. The principle is that the specific surface area, iron-phosphorus ratio, particle size and other indicators of iron phosphate have a crucial influence on the "activity" of iron phosphate, and will directly affect the size of the sintered lithium iron phosphate particles. Specifically, the activity of high iron-phosphorus ratio and low specific surface iron phosphate is relatively low, and the sintered lithium iron phosphate is not easy to bond and fuse, and the resulting lithium iron phosphate particles are usually small in size. Iron phosphate with a low iron-phosphorus ratio, high specific surface area and a small primary particle size has a relatively high activity. During the sintering process, multiple small particles will bond, agglomerate and fuse to form large-sized lithium iron phosphate particles. The single-crystal-like high iron-phosphorus ratio dense iron phosphate material provided by the present invention has a low specific surface area (1-4 m 2 / g), high iron-phosphorus ratio (0.975-0.985), dense particles, low activity, and can be sintered to form round, monodispersed, small-sized lithium iron phosphate particles. Conventional iron phosphate has a high specific surface area (6-11 m 2 / g), low iron-phosphorus ratio (0.955-0.975), small primary particle size, high activity, and can be sintered to form large-sized lithium iron phosphate particles. Therefore, mixing single-crystal-like high iron-phosphorus ratio dense iron phosphate with conventional iron phosphate to prepare lithium iron phosphate materials can form lithium iron phosphate materials with both small-sized particles and large-sized particles.

[0016] Compared with the prior art, the present invention has the following beneficial effects: 1. The use of the iron phosphate provided by the present invention and conventional iron phosphate to prepare lithium iron phosphate can effectively control the proportion of small-particle lithium iron phosphate. The principle is that the iron phosphate material provided by the present invention has a unique single-crystal dense morphology, and the primary particle size is large enough. In the process of preparing lithium iron phosphate, when the slurry D50 is ground to a degree of several hundred nanometers, in the conventional iron phosphate slurry, the "particles" with D50 of several hundred nanometers are loose and porous secondary agglomerates composed of multiple primary particles with a size of tens of nanometers, while in the single-crystal dense iron phosphate slurry, the "particles" with D50 of several hundred nanometers are dense and compact single particles composed of single primary particles with a size of several hundred nanometers. During sintering, the loose and porous secondary agglomerates are easy to melt and grow to form large-particle lithium iron phosphate, while the dense and compact single particles will only form lithium iron phosphate with a small particle size. Therefore, by controlling the mixed proportion of single-crystal dense iron phosphate, the proportion of small particles in the finished lithium iron phosphate product can be controlled. By controlling the particle size of the single crystal dense iron phosphate during grinding, the size of small particles in the finished lithium iron phosphate product can be controlled.

[0017] 2. The principle of the high iron-phosphorus ratio dense type ferric phosphate with a single crystal provided by the present invention is that the present invention prepares ferric phosphate through a ferrous phosphate intermediate route (Fe3(PO4)2·8H2O), while the prior art usually prepares ferric phosphate through a basic ammonium ferric phosphate intermediate route (NH4Fe2(PO4)2OH·2H2O). The theoretical molar ratio of iron to phosphorus in the ferrous phosphate intermediate (3:2) is significantly higher than the theoretical molar ratio of iron to phosphorus in basic ammonium ferric phosphate (1:1), and the finished ferric phosphate produced by this route has a higher iron-phosphorus ratio. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Scanning electron micrographs of ferric phosphate dihydrate (left), ferric phosphate dihydrate slices (middle), and anhydrous ferric phosphate (right) prepared in Experiment 1; Figure 2 Scanning electron micrographs of ferric phosphate dihydrate (left) and anhydrous ferric phosphate (right) prepared in Experiment 2; Figure 3 Scanning electron micrographs of ferric phosphate dihydrate (left) and anhydrous ferric phosphate (right) prepared in Experiment 3; Figure 4Scanning electron micrographs of dihydrate iron phosphate (left) and anhydrous iron phosphate (right) prepared in Experiment 4. DETAILED DESCRIPTION

[0019] Example 1 A single crystal dense iron phosphate material, the iron phosphate material is prepared by the following steps: S1. Prepare 0.5 mol / L phosphate solution and 0.5 mol / L ferrous salt solution respectively, add a certain amount of pure water into the reactor as a base, add the ferrous salt solution and the phosphate solution at 30°C, the feeding time is 0.5 h, and react for 1 h after the feeding is completed to obtain ferrous phosphate slurry A; S2, subjecting the ferrous phosphate slurry A obtained in step S1 to solid-liquid separation and washing to obtain a ferrous phosphate filter cake; S3, prepare 40wt% phosphoric acid solution and 10wt% hydrogen peroxide solution respectively, slurry the ferrous phosphate filter cake obtained in step S2 with pure water, stir evenly and transfer into a reactor, continue stirring and heat to 80°C, mix the phosphoric acid solution and hydrogen peroxide solution and add, keep warm and react for 0.5 h, and obtain white slurry B; S4. The slurry B obtained in step S3 is subjected to solid-liquid separation, washing treatment, and flash drying to obtain ferric phosphate dihydrate. The ferric phosphate dihydrate is subjected to calcination treatment to obtain the single-crystal-like high iron-phosphorus ratio dense ferric phosphate material.

[0020] Preferably, the phosphate solution in step S1 is prepared from ammonium monohydrogen phosphate.

[0021] Preferably, the ferrous salt solution is prepared from ferrous sulfate.

[0022] Preferably, the molar ratio of iron to phosphorus in the ferrous salt solution and the phosphate salt solution is controlled to be 1:0.9.

[0023] Preferably, in step S3, the molar ratio of the phosphorus element after the phosphoric acid solution and the hydrogen peroxide solution are mixed to the iron element in the ferrous phosphate slurry A obtained in step S1 is n(P):n(Fe)=0.10:1.

[0024] Preferably, in step S3, the phosphoric acid solution and the hydrogen peroxide solution are mixed and added within 30 minutes.

[0025] Preferably, it is characterized in that the primary particle size of the single-crystal-like dense iron phosphate material is 1 μm.

[0026] Example 2 A single crystal dense iron phosphate material, the iron phosphate material is prepared by the following steps: S1. Prepare 1.5 mol / L phosphate solution and 1.5 mol / L ferrous salt solution respectively, add a certain amount of pure water into the reactor as the base, add the ferrous salt solution and the phosphate solution at 60°C, the feeding time is 3 hours, react for 3 hours after the feeding is completed, and obtain ferrous phosphate slurry A; S2, subjecting the ferrous phosphate slurry A obtained in step S1 to solid-liquid separation and washing to obtain a ferrous phosphate filter cake; S3, prepare 85wt% phosphoric acid solution and 25wt% hydrogen peroxide solution respectively, slurry the ferrous phosphate filter cake obtained in step S2 with pure water, stir evenly and transfer into a reactor, continue stirring and heat to 100°C, mix the phosphoric acid solution and the hydrogen peroxide solution and add, keep warm and react for 3 h, and obtain white slurry B; S4. The slurry B obtained in step S3 is subjected to solid-liquid separation, washing treatment, and flash drying to obtain ferric phosphate dihydrate. The ferric phosphate dihydrate is subjected to calcination treatment to obtain the single-crystal-like high iron-phosphorus ratio dense ferric phosphate material.

[0027] Preferably, the phosphate solution in step S1 is prepared from sodium dihydrogen phosphate.

[0028] Preferably, the ferrous salt solution is prepared from ferrous chloride.

[0029] Preferably, the molar ratio of iron to phosphorus in the ferrous salt solution and the phosphate salt solution is controlled to be 1:1.2.

[0030] Preferably, in step S3, the molar ratio of the phosphorus element after the phosphoric acid solution and the hydrogen peroxide solution are mixed to the iron element in the ferrous phosphate slurry A obtained in step S1 is n(P):n(Fe)=0.80:1.

[0031] Preferably, in step S3, the phosphoric acid solution and the hydrogen peroxide solution are mixed and added within 90 minutes.

[0032] Preferably, it is characterized in that the primary particle size of the single-crystal-like dense iron phosphate material is 10 μm.

[0033] Example 3 A single crystal dense iron phosphate material, the iron phosphate material is prepared by the following steps: S1. Prepare 1 mol / L phosphate solution and 1 mol / L ferrous salt solution respectively, add a certain amount of pure water into the reactor as a base, add the ferrous salt solution and the phosphate solution at 40°C, the feeding time is 2 h, react for 2 h after the feeding is completed, and obtain ferrous phosphate slurry A; S2, subjecting the ferrous phosphate slurry A obtained in step S1 to solid-liquid separation and washing to obtain a ferrous phosphate filter cake; S3, prepare 60wt% phosphoric acid solution and 18wt% hydrogen peroxide solution respectively, slurry the ferrous phosphate filter cake obtained in step S2 with pure water, stir evenly and transfer into a reactor, continue stirring and heat to 90°C, mix the phosphoric acid solution and hydrogen peroxide solution and add, keep warm and react for 2 h, and obtain white slurry B; S4. The slurry B obtained in step S3 is subjected to solid-liquid separation, washing treatment, and flash drying to obtain ferric phosphate dihydrate. The ferric phosphate dihydrate is subjected to calcination treatment to obtain the single-crystal-like high iron-phosphorus ratio dense ferric phosphate material.

[0034] Preferably, the phosphate solution in step S1 is prepared from ammonium phosphate.

[0035] Preferably, the ferrous salt solution is prepared from ferrous nitrate.

[0036] Preferably, the molar ratio of iron element to phosphorus element in the ferrous salt solution and the phosphate salt solution is controlled to be 1:1.

[0037] Preferably, in step S3, the molar ratio of the phosphorus element after the phosphoric acid solution and the hydrogen peroxide solution are mixed to the iron element in the ferrous phosphate slurry A obtained in step S1 is n(P):n(Fe)=0.50:1.

[0038] Preferably, in step S3, the phosphoric acid solution and the hydrogen peroxide solution are mixed and added within 60 minutes.

[0039] Preferably, it is characterized in that the primary particle size of the single-crystal-like dense iron phosphate material is 5 μm.

[0040] Experimental Section

[0041] Experiment 1 A single-crystal-like dense iron phosphate material is prepared by using the technical solution of the present invention, comprising the following steps: S1. Weigh 460 g of ammonium dihydrogen phosphate, dissolve and dilute to 4 L to obtain a phosphate solution, weigh 1112 g of ferrous sulfate heptahydrate, dissolve and dilute to 4 L to obtain a ferrous solution. Add the ferrous solution and phosphate together for 0.5 h, heat to 30°C, react for 1 h after adding, and obtain ferrous phosphate slurry A.

[0042] S2. The ferrous phosphate slurry A is subjected to solid-liquid separation and washing to obtain a filter cake.

[0043] S3. Slurry the filter cake, raise the temperature to 85°C, add 230 g phosphoric acid and 270 g hydrogen peroxide, and keep warm for 1 h to obtain white slurry B.

[0044] S4. The white slurry B is subjected to solid-liquid separation and washing to obtain a filter cake, which is flash-dried to obtain dihydrated iron phosphate, which is calcined to obtain anhydrous iron phosphate.

[0045] Figure 1 Scanning electron microscope images of ferric phosphate dihydrate, ferric phosphate dihydrate slices and anhydrous ferric phosphate prepared for this experiment. As shown in the figure, the primary particles of ferric phosphate dihydrate are about 10 μm, and there are almost no pores in the electron microscope of the slice of ferric phosphate dihydrate. The primary particles of anhydrous ferric phosphate are about 30 μm, which is characterized by large and dense particles.

[0046] Experiment 2 A single-crystal-like dense iron phosphate material is prepared by using the technical solution of the present invention, comprising the following steps: S1. Weigh 552 g of ammonium dihydrogen phosphate, dissolve and dilute to 4 L to obtain a phosphate solution, weigh 1334 g of ferrous sulfate heptahydrate, dissolve and dilute to 4 L to obtain a ferrous solution. Add the ferrous solution and phosphate together for 0.5 h, heat to 50 ° C, react for 1 h after adding, and obtain ferrous phosphate slurry A.

[0047] S2. The ferrous phosphate slurry A is subjected to solid-liquid separation and washing to obtain a filter cake.

[0048] S3. Slurry the filter cake, raise the temperature to 90°C, add 277 g phosphoric acid and 354 g hydrogen peroxide, and keep warm for 2 h to obtain white slurry B.

[0049] S4. The white slurry B is subjected to solid-liquid separation and washing to obtain a filter cake, which is flash-dried to obtain dihydrated iron phosphate, which is calcined to obtain anhydrous iron phosphate.

[0050] Figure 2 This is the scanning electron microscope image of the dihydrated ferric phosphate and anhydrous ferric phosphate prepared in this experiment. As shown in the figure, the primary particles of dihydrated ferric phosphate are about 10 μm, the secondary agglomerates are about 30 μm, and the primary particles of anhydrous ferric phosphate are about 30 μm, which are characterized by large and dense particles.

[0051] Experiment 3 This experiment is a method for preparing conventional morphology iron phosphate. The steps are similar to those of Experiment 1, and the reaction ratio is the same. The difference from Experiment 1 is that the position of adding hydrogen peroxide is different, that is, in this experiment, the hydrogen peroxide solution is added to the ferrous phosphate solution during the synthesis stage. The specific steps are as follows: S1. Weigh 460 g of ammonium dihydrogen phosphate, dissolve it and dilute it to 4 L to obtain a phosphate solution. Weigh 1112 g of ferrous sulfate heptahydrate, dissolve it and dilute it to 4 L to obtain a ferrous salt solution. Add the ferrous solution and the phosphate solution together for 0.5 h. Heat to 30°C, add 270 g of hydrogen peroxide, and react for 1 h to obtain slurry A.

[0052] S2. Slurry A is subjected to solid-liquid separation and washing to obtain a filter cake.

[0053] S3. Slurry the filter cake, raise the temperature to 85°C, add 230 g of phosphoric acid, and keep warm for 1 h to obtain white slurry B.

[0054] S4. The white slurry B is subjected to solid-liquid separation and washing to obtain a filter cake, which is flash-dried to obtain dihydrated iron phosphate, which is calcined to obtain anhydrous iron phosphate.

[0055] Figure 3 The morphology of the dihydrated iron phosphate and anhydrous iron phosphate prepared in Experiment 3 is shown. It can be seen from the figure that the primary particles of the dihydrated iron phosphate are significantly smaller than those in Experiment 1, and the primary particles are accumulated into flake-like secondary particles, and the secondary particles are aggregated into spherical aggregates. The reason for the difference in morphology may be that the hydrogen peroxide solution is added to the ferrous phosphate solution, and Fe 2+ Rapidly oxidized to Fe 3+ , Fe 3+ Fast and PO4 3- The nucleation rate is fast and the grain growth rate is slow, so the formed grains are small.

[0056] Experiment 4 This experiment is a method for preparing conventional morphology ferric phosphate, which has the same ratio and reaction conditions as Experiment 2. The difference from Experiment 2 is that this experiment adopts the common feeding method in the prior art, that is, ferrous salt solution is used as the base liquid, and phosphate solution and hydrogen peroxide solution are used as the feeding liquid. The specific steps are as follows: S1. Weigh 552 g of ammonium dihydrogen phosphate and 354 g of hydrogen peroxide, mix and stir evenly and dilute to 4 L to obtain a phosphorus-oxygen mixed solution. Weigh 1334 g of ferrous sulfate heptahydrate, dissolve and dilute to 4 L to obtain a ferrous salt solution. Use the ferrous solution as the base liquid, feed for 0.5 h, and heat to 50°C. Add the phosphorus-oxygen mixed solution, react for 60 min after adding, and obtain slurry A.

[0057] S2. Slurry A is subjected to solid-liquid separation and washing to obtain a filter cake.

[0058] S3. Slurry the filter cake, raise the temperature to 90°C, add 277 g of phosphoric acid, and keep warm for 2 h to obtain white slurry B.

[0059] S4. The white slurry B is subjected to solid-liquid separation and washing to obtain a filter cake, which is flash-dried to obtain dihydrated iron phosphate, which is calcined to obtain anhydrous iron phosphate.

[0060] Figure 4The morphology of dihydrate iron phosphate and anhydrous iron phosphate prepared in this experiment is shown. It can be seen from the figure that the primary particles of dihydrate iron phosphate are not densely stacked, but are orderly arranged and stacked into flaky particles. The flaky particles are cross-stacked at a certain angle to form spherical agglomerates. Anhydrous iron phosphate inherits the morphology of dihydrate iron phosphate, with smaller primary particles and loose stacking between agglomerates.

[0061] Experiment 5 Table 1 shows the iron-phosphorus ratio and tap density of the anhydrous ferric phosphate prepared in Experiments 1-4. Experiments 1 and 2 adopted the technical solution of the present invention. Due to the high density of the particles, the tap density of the ferric phosphate was significantly higher than that of Experiments 3 and 4.

[0062] In experiment 3, a hydrogen peroxide solution was added to a ferrous phosphate solution during the synthesis stage. In experiment 4, a ferrous salt solution was used as a base solution, and a phosphate salt solution and a hydrogen peroxide solution were used as feed solutions. The iron-phosphorus ratio and the tap density of the prepared ferric phosphate were worse than those of experiments 1 and 2 (the present invention).

[0063] Table 1 Indices of iron phosphate prepared in Experiments 1-4

[0064] In summary, the iron phosphate prepared in the present application has the characteristics of quasi-single crystal, high iron-phosphorus ratio, and dense type, and the microscopic primary particle morphology shows dispersion; further, during the calcination process, due to the strong crystallinity of iron phosphate dihydrate, no melting phenomenon occurs after calcination, and the morphological characteristics are maintained.

Claims

1. A single crystal dense iron phosphate material, characterized in that: The iron phosphate material is prepared by the following steps: S1. Prepare 0.5-1.5 mol / L phosphate solution and 0.5-1.5 mol / L ferrous salt solution respectively, add a certain amount of pure water into the reactor as the base, add the ferrous salt solution and the phosphate solution at 30-60°C, the feeding time is 0.5-3 h, react for 1-3 h after the feeding is completed, and obtain ferrous phosphate slurry A; S2, subjecting the ferrous phosphate slurry A obtained in step S1 to solid-liquid separation and washing to obtain a ferrous phosphate filter cake; S3, prepare 40-85wt% phosphoric acid solution and 10-25wt% hydrogen peroxide solution respectively, slurry the ferrous phosphate filter cake obtained in step S2 with pure water, stir evenly and transfer into a reactor, continue stirring and heat to 80-100°C, mix the phosphoric acid solution and the hydrogen peroxide solution and add, keep warm and react for 0.5-3 h, and obtain white slurry B; S4. The slurry B obtained in step S3 is subjected to solid-liquid separation, washing treatment, and flash drying to obtain ferric phosphate dihydrate. The ferric phosphate dihydrate is subjected to calcination treatment to obtain the single-crystal-like high iron-phosphorus ratio dense ferric phosphate material.

2. The single crystal dense iron phosphate material according to claim 1, characterized in that: The phosphate solution in step S1 is prepared from any one of ammonium monohydrogen phosphate, ammonium dihydrogen phosphate, ammonium phosphate, phosphoric acid, sodium monohydrogen phosphate, sodium dihydrogen phosphate, and sodium phosphate.

3. The single crystal dense iron phosphate material according to claim 1, characterized in that: The ferrous salt solution is prepared from any one of ferrous sulfate, ferrous nitrate, ferrous chloride, iron powder and iron sheet.

4. The single crystal dense iron phosphate material according to claim 1, characterized in that: The molar ratio of the iron element to the phosphorus element in the ferrous salt solution and the phosphate salt solution is controlled to be 1:0.9-1:1.

2.

5. The single crystal dense iron phosphate material according to claim 1, characterized in that: In step S3, the molar ratio of the phosphorus element after the phosphoric acid solution and the hydrogen peroxide solution are mixed to the iron element in the ferrous phosphate slurry A obtained in step S1 is n(P):n(Fe)=0.10-0.80:

1.

6. The single crystal dense iron phosphate material according to claim 1, characterized in that: In step S3, the phosphoric acid solution and the hydrogen peroxide solution are mixed and added within 30-90 minutes.

7. A single-crystal-like dense iron phosphate material according to any one of claims 1 to 6, characterized in that: The primary particle size of the single-crystal dense iron phosphate material is 1-10 μm; The single crystal dense iron phosphate material has an iron-phosphorus ratio of 0.975-0.985, an iron content of 36.5-37.5%, a phosphorus content of 20.55-20.75%, and a specific surface area of ​​1-4 m 2 / g.

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