Iron phosphate as well as preparation method and application thereof

Abstract

The invention provides iron phosphate as well as a preparation method and application thereof, and relates to the technical field of lithium ion batteries. Specifically, the method comprises the following steps: preparing a raw material solution from a ferrous sulfate crude salt of a titanium dioxide production by-product, heating the raw material solution to boil, and cooling to obtain a mixed solution; then carrying out solid-liquid separation to obtain recrystallized ferric salt and preparing into a ferric salt solution; adjusting the pH value of the ferric salt solution to be lower than 1.80, repeatedly boiling, cooling and crystallizing to obtain secondary crystallized ferric salt, and preparing into a second ferric salt solution; preparing a phosphorus salt solution from monoammonium phosphate and ammonia water; mixing the second ferric salt solution, the phosphorus salt solution and hydrogen peroxide, reacting, and separating to obtain an iron phosphate precursor; and preparing the iron phosphate precursor into slurry, adjusting the pH value, and sequentially carrying out heating reaction, solid-liquid separation and calcination after the slurry becomes white to obtain iron phosphate. According to the method, resource utilization of the ferrous sulfate crude salt byproduct is realized, and meanwhile, the defects of high impurity content and low product purity during resource product preparation are overcome.

Description

Technical Field

[0001] The present invention relates to the technical field of lithium ion batteries, and in particular to iron phosphate and a preparation method and application thereof. Background Art

[0002] At present, most titanium dioxide enterprises in my country use sulfuric acid method or chlorination method to produce titanium dioxide. Among them, sulfuric acid method can use low-grade ilmenite as raw material, with relatively low production cost, mature technology and simple equipment, so it has been widely used. Specifically, the sulfuric acid method for producing titanium dioxide mainly includes the following processes: ore pretreatment (grinding, drying and magnetic separation of ilmenite or titanium slag to remove impurities and refine particles), acid hydrolysis (the pretreated ilmenite or titanium slag is subjected to acid hydrolysis reaction with concentrated sulfuric acid at a certain temperature to generate ferrous sulfate and titanic acid), sedimentation and filtration (the cooled acid hydrolysis liquid is subjected to sedimentation and filtration to remove solid inert substances and unreacted raw material residues), hydrolysis (the soluble sulfate titanium oxide is hydrolyzed to obtain water-insoluble titanium precipitate and separated), calcination (the hydrolyzed titanium solid phase is converted or purified by calcination to obtain titanium dioxide), post-treatment (including wet grinding, drying, air flow crushing and coating). A large amount of ferrous sulfate crystals are obtained during the acid hydrolysis and filtration stages, and about 2.5 to 3.5 tons of ferrous sulfate crystals are produced as byproducts for every ton of titanium dioxide produced. However, the purity of such ferrous sulfate crystals is generally less than 90%, and they contain a lot of impurities (such as Ti, Mg, Al, Mn, etc.), which cannot be used directly. They are piled up as waste for a long time, which wastes resources and harms the environment.

[0003] For example, patent CN202311002905.8 discloses a method for purifying, refining and crystallizing ferrous sulfate, a byproduct of titanium dioxide, comprising: 1) under stirring conditions, dissolving the titanium dioxide raw material containing the byproduct ferrous sulfate in a mixed solution of ferrous sulfate heptahydrate at 60 to 80°C, then adding iron powder for reduction, adding acid to adjust the pH to 1 to 3, adding a flocculant for flocculation, and obtaining a clear liquid; 2) under stirring conditions, the obtained clear liquid is divided into three stages for cooling crystallization and solid-liquid separation to obtain a primary crystallization crude product; 3) under stirring conditions, the obtained primary crystallization crude product is dissolved in water at 60 to 80°C, and cooled and crystallized in three stages to obtain ferrous sulfate, a byproduct of titanium dioxide. This process can continuously, stably and efficiently prepare ferrous sulfate heptahydrate products in large quantities, so as to be used for the preparation of battery-grade ferrous oxalate. However, the cooling and crystallization method involved in its purification process is relatively complicated, and a large amount of crystal seeds need to be added in the first cooling of the three cooling stages. This method is not suitable for large-scale application in actual production.

[0004] In view of this, the present invention is proposed. Summary of the invention

[0005] The first object of the present invention is to provide a preparation method of iron phosphate, which is used to realize the resource utilization of ferrous sulfate crude salt as a by-product of titanium dioxide production, and at the same time solve the defects of high impurities and low product purity existing in the preparation of resource-based products from ferrous sulfate crude salt.

[0006] The second object of the present invention is to provide an iron phosphate with high purity, which effectively removes high-content and various impurities in the raw material crude salt.

[0007] The third object of the present invention is to provide a lithium iron phosphate, which has better safety, stability and electrical properties in the field of cathode materials based on high-purity iron phosphate raw materials.

[0008] The fourth object of the present invention is to provide a lithium ion battery.

[0009] The fifth object of the present invention is to provide an electrical equipment.

[0010] In order to achieve the above objects of the present invention, the following technical solutions are specifically adopted:

[0011] A preparation method of iron phosphate includes the following steps:

[0012] (1) Prepare the ferrous sulfate crude salt as a by-product of titanium dioxide production into a raw material solution;

[0013] (2) After heating the raw material solution to boiling and then cooling it, obtain a mixed solution; separate the solid and liquid of the mixed solution to obtain recrystallized iron salt;

[0014] (3) Prepare the recrystallized iron salt into an iron salt solution, adjust the pH of the iron salt solution to less than 1.80, and then repeat step (2) to obtain secondary crystallized iron salt;

[0015] (4) Prepare the secondary crystallized iron salt into a second iron salt solution; prepare a phosphate solution with monoammonium phosphate and ammonia water; mix and react the second iron salt solution, the phosphate solution and hydrogen peroxide, and then separate the solid and liquid to obtain an iron phosphate precursor;

[0016] (5) Prepare the iron phosphate precursor into a precursor slurry, adjust the pH to 1.6 ± 0.2, and after it turns white, carry out a temperature-rising reaction, solid-liquid separation and calcination in sequence to obtain iron phosphate.

[0017] An iron phosphate is prepared by using the preparation method of iron phosphate described above.

[0018] A lithium iron phosphate is prepared by using the iron phosphate described above.

[0019] A lithium ion battery is prepared by using the iron phosphate or the lithium iron phosphate described above.

[0020] An electrical device includes the lithium-ion battery described above.

[0021] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0022] The present invention provides a method and application for preparing high-purity iron phosphate from by-product ferrous sulfate crystals of titanium dioxide. On the one hand, from the perspective of crude iron salts, its purification method is simpler than the reported experimental processes and is more suitable for industrial applications. On the other hand, from the perspective of iron phosphate preparation, the iron phosphate prepared by the present invention has lower impurity content, meeting the strict requirements for the impurity content of iron phosphate in the battery field. Specific embodiments

[0023] The technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments. However, those skilled in the art will understand that the following described embodiments are some embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention and should not be construed as limiting the scope of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the scope of protection of the present invention. For those conditions not specified in the embodiments, they shall be carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase. In addition, the terms "first", "second", and "third" are only used for descriptive purposes and cannot be construed as indicating or implying relative importance.

[0024] The first aspect of the present invention is to provide a method for preparing iron phosphate, which mainly includes the following processes: preparing a solution, heating and dissolving, recrystallization, secondary crystallization, reaction of an iron source and a phosphorus source, and purification. Specifically, it includes the following steps (1) to (5).

[0025] (1) Prepare a raw material solution from the crude ferrous sulfate salt as a by-product of titanium dioxide production.

[0026] The crude ferrous sulfate salt used in the present invention is mainly produced in the acidolysis stage of the sulfuric acid method for titanium dioxide production. Specifically, it is a by-product obtained by subjecting pretreated ilmenite or titanium slag to an acidolysis reaction with concentrated sulfuric acid at a certain temperature. Due to the limitation of the initial raw material ilmenite, impurity elements such as calcium, magnesium, manganese, silicon, aluminum, vanadium, and chromium may inevitably exist in the ilmenite, and most of them are discharged together with the mother liquor after acidolysis. After concentration and separation, salt crystals mainly composed of ferrous sulfate are obtained by combination.

[0027] As a preferred embodiment, the crude ferrous sulfate contains the following impurity components: Ca 20 ppm to 100 ppm, Cd < 10 ppm, Cr < 10 ppm, Mg 2000 ppm to 4000 ppm, Mn 400 ppm to 1500 ppm, Ni < 50 ppm, Pb < 10 ppm, Zn < 100 ppm, Al < 100 ppm, Ti < 4180 ppm.

[0028] As a preferred embodiment, the total iron content in the crude ferrous sulfate is 12 wt.% to 24 wt.%; specifically, the total iron content mainly exists in the form of divalent iron, but there is also a very small amount of trivalent iron. In some alternative embodiments, the content ratio of divalent iron to total iron is ≥ 95%.

[0029] As a preferred embodiment, the solvent of the raw material liquid is deionized water; in the raw material liquid, the total iron content is 80 g / L to 100 g / L.

[0030] (2) After heating the raw material liquid to boiling and then cooling it, a mixed liquid is obtained; the mixed liquid is subjected to solid-liquid separation to obtain recrystallized iron salt.

[0031] As a preferred embodiment, for the heating to boiling, the time of maintaining boiling is based on the volume change of the raw material liquid. When the volume of the mixed liquid is reduced to 40% to 60%, heating is stopped.

[0032] As a preferred embodiment, for the cooling, the temperature is reduced and the mixture is left standing at room temperature, and the room temperature can refer to 20°C to 30°C; in some more preferred embodiments, the time for temperature reduction is 2 min to 4 min, and the time for standing is 3 h to 5 h.

[0033] In the present invention, through the treatment of heating to boiling and cooling reaction, on the one hand, the ferrous crude salt reacts to be converted into iron ions in the solution, and on the other hand, the iron salt solution is concentrated during the heating reaction process to increase the iron salt concentration.

[0034] As a preferred embodiment, in the present invention, the solid-liquid separation includes but is not limited to decantation, filtration, centrifugal separation, filter screen or membrane separation, etc.; in a more preferred embodiment, the solid-liquid separation in this step is carried out by suction filtration in a low-production mode or a laboratory scenario, while in a batch production mode, the solid-liquid separation can be carried out through a filter screen.

[0035] (3) The recrystallized iron salt is formulated into an iron salt solution. After adjusting the pH of the iron salt solution to be lower than 1.80, step (2) is repeated to obtain a secondary crystallized iron salt.

[0036] As a preferred embodiment, the solvent of the iron salt solution is deionized water; in the iron salt solution, the total iron content is 80 g / L to 100 g / L.

[0037] As a preferred embodiment, the pH of the iron salt solution is 1.0 to 1.78, including but not limited to any one or any numerical range composed of any two of 1.0, 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.7, 1.75.

[0038] As a preferred embodiment, the acid reagent used for pH adjustment includes at least one of hydrochloric acid, sulfuric acid, nitric acid, etc.

[0039] As a preferred embodiment, repeatedly performing step (2) includes the following steps: heating the iron salt solution after pH adjustment to boiling and then cooling to obtain a second mixed solution; performing solid-liquid separation on the second mixed solution to obtain secondary crystalline iron salt.

[0040] (4) Prepare the secondary crystalline iron salt into a second iron salt solution; prepare a phosphate salt solution with ammonium dihydrogen phosphate and ammonia water; mix and react the second iron salt solution, the phosphate salt solution and hydrogen peroxide, and then perform solid-liquid separation to obtain a ferric phosphate precursor.

[0041] As a preferred embodiment, the solvent of the second iron salt solution is deionized water; in the second iron salt solution, the total iron content is 50 g / L to 70 g / L; in some more preferred embodiments, the total iron content is 58 g / L to 62 g / L.

[0042] As a preferred embodiment, the preparation method of the phosphate salt solution includes the following steps: mix the ammonium dihydrogen phosphate with water, and then add ammonia water until the pH of the solution is 6.8 to 7.2 to obtain the phosphate salt solution.

[0043] As a preferred embodiment, the phosphorus content of the phosphate salt solution is 2.3 wt.% to 2.7 wt.%.

[0044] As a preferred embodiment, based on the iron atoms of the second iron salt solution, based on the phosphorus atoms of the phosphate salt solution, and based on the molecules of hydrogen peroxide in hydrogen peroxide, the molar ratio of the second iron salt solution, the phosphate salt solution and hydrogen peroxide is 1:1:(0.75 to 1).

[0045] As a preferred embodiment, the temperature of the mixing reaction is 55°C to 65°C, and the time of the mixing reaction is 1.8 h to 2 h; in some alternative embodiments, the temperature of the mixing reaction includes, but is not limited to, any one or any numerical range formed by any two of 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65 (°C), and the time of the mixing reaction includes, but is not limited to, any one or any numerical range formed by any two of 1.8, 1.82, 1.85, 1.88, 1.9, 1.92, 1.95, 1.98, 2 (h).

[0046] As a preferred embodiment, after the solid-liquid separation, it further includes a process of washing the iron phosphate precursor with deionized water; and those skilled in the art can adaptively adjust parameters such as the flow rate and number of times of the water washing according to the actual situation.

[0047] (5) Prepare the iron phosphate precursor into a precursor slurry, adjust the pH to 1.6 ± 0.2, and after it turns white, carry out a temperature-raising reaction, solid-liquid separation, and calcination in sequence to obtain iron phosphate.

[0048] As a preferred embodiment, the solvent of the precursor slurry is deionized water, and the solid content of the precursor slurry is 10% to 15%.

[0049] As a preferred embodiment, phosphoric acid is used as the acid reagent for adjusting the pH to avoid introducing impurities due to the type of acid.

[0050] As a preferred embodiment, the temperature of the temperature-raising reaction is 80°C to 95°C, and the time of the temperature-raising reaction is 0.5 h to 2 h; in some alternative embodiments, the temperature of the temperature-raising reaction includes, but is not limited to, any one or any numerical range formed by any two of 80, 82, 85, 88, 90, 92, 95 (°C), and the time of the temperature-raising reaction includes, but is not limited to, any one or any numerical range formed by any two of 0.5, 0.6, 0.8, 1, 1.2, 1.5, 1.8, 2 (h).

[0051] As a preferred embodiment, the temperature of the calcination is 550°C to 600°C, and the time of the calcination is 1.5 h to 2.5 h; in some alternative embodiments, the temperature of the calcination includes, but is not limited to, any one or any numerical range formed by any two of 550, 555, 560, 565, 570, 575, 580, 585, 590, 595, 600 (°C), and the time of the calcination includes, but is not limited to, any one or any numerical range formed by any two of 1.5, 1.6, 1.7, 1.8, 1.9, 2, 2.1, 2.2, 2.3, 2.4, 2.5 (h).

[0052] The second aspect of the present invention is to provide a ferric phosphate, which is prepared by using the preparation method of ferric phosphate described in the first aspect.

[0053] The third aspect of the present invention is to provide a lithium iron phosphate, which is prepared by using the ferric phosphate described in the second aspect. It can be understood that the present invention does not impose any restrictions on the preparation method of the lithium iron phosphate; those skilled in the art can prepare it based on the ferric phosphate as a raw material in a conventional or unconventional manner. Conventional methods include, but are not limited to, solid-phase processes such as carbothermal reduction method and high-temperature solid-phase method, or liquid-phase processes such as hydrothermal method and self-heating evaporation method. At the same time, it can be prepared by grading based on other exogenous ferric phosphates.

[0054] The fourth aspect of the present invention is to provide a lithium-ion battery, which is prepared by using the ferric phosphate described in the second aspect or the lithium iron phosphate described in the third aspect. It can be understood that the lithium-ion battery should include positive and negative electrodes, electrolyte, separator, and other necessary or non-necessary functional elements or packaging components, etc. Those skilled in the art can make any selection and combination thereof; when the lithium-ion battery contains the ferric phosphate or lithium iron phosphate described in the present invention, a lithium-ion battery positive electrode should be prepared first based on the ferric phosphate or lithium iron phosphate. The positive electrode can be a lithium iron phosphate positive electrode or a composite positive electrode containing lithium iron phosphate; that is, regardless of whether other positive electrode active materials are also used in the lithium-ion battery, it can be regarded as an embodiment of the present invention.

[0055] The fifth aspect of the present invention is to provide an electrical equipment, including the lithium-ion battery described in the fourth aspect. The electrical equipment can be any equipment or device that depends on electric energy for work or operation, including but not limited to new energy vehicles, building electrical equipment, industrial electrical appliances, household and agricultural electrical appliances, etc.; when including the lithium-ion battery, any electrical equipment equipped with the lithium-ion battery can belong to an embodiment of the present invention.

[0056] Example 1

[0057] Step S1: Prepare a ferric salt solution A with a total iron content of 90 g / L by using deionized water to dissolve the by-product crude ferric salt crystals from titanium dioxide production by sulfuric acid method; the component content of the crude ferric salt crystals is provided as shown in Table 1 below.

[0058] Table 1

[0059] Impurity elements Crude iron salt crystals Ca (ppm) 49.76 Cd (ppm) 1.46 Cr (ppm) 0.68 K (ppm) 1.28 Mg (ppm) 2772.61 Mn (ppm) 885.50 Ni (ppm) 16.03 Pb (ppm) 1.53 Zn (ppm) 32.99 Al (ppm) 27.38 Co (ppm) 0.00 Na (ppm) 119.18 Cu (ppm) 0.00 Ti (ppm) 3921.94 Total Fe (%) 16.31 <![CDATA[Fe 2+ (%)]]> 16.30

[0060] Step S2: Heat the solution A to boiling, and after the solution volume is reduced by half, remove it from the heating device.

[0061] Step S3: After the above hot solution is cooled for 4 min, stir it at a rate of 500 rpm at room temperature for 4 h to obtain a solid-liquid mixture B.

[0062] Step S4: Filter the mixture B to separate the solid and liquid, and the obtained filter cake is the primary recrystallized iron salt crystal C.

[0063] Step S5: Prepare the crystal C into an iron salt solution D with a total iron content of 90 g / L using deionized water.

[0064] Step S6: Adjust the pH of the solution D to 1.60 using dilute sulfuric acid to obtain a solution E.

[0065] Step S7: Perform secondary recrystallization on the solution E according to Steps S2 - S4 to obtain the secondary recrystallized iron salt crystal F.

[0066] Step S8: Prepare the crystal F into an iron salt solution with a total iron content of 60 g / L to obtain an iron salt solution G.

[0067] Step S9: Prepare a solution with a phosphorus content of 2.5 wt.% using industrial monoammonium phosphate as the phosphorus source, and then adjust the pH to 7.0 ± 0.1 with ammonia water to obtain a phosphate salt H.

[0068] Step S10: Feed the above iron salt solution G, phosphate salt H, and hydrogen peroxide according to a molar ratio of Fe:P:H₂O₂ of 1:1:0.75, with a reaction temperature of 60 °C and a reaction time of 2 h to obtain a mixed slurry I.

[0069] Step S11: After filtering the slurry I, wash it with deionized water, and the obtained filter cake is the amorphous iron phosphate J.

[0070] Step S12: Prepare the filter cake J into a slurry with a solid content of 12%, adjust the reaction pH to 1.6 ± 0.2 using phosphoric acid to obtain a mixed slurry. After it turns white, raise the temperature of the system to 90 °C and stir it at a constant temperature for 1 h to obtain a reaction slurry K.

[0071] Step S13: The solid obtained after filtering, washing, and drying the slurry K is calcined at 575 °C for 1.8 h to obtain the iron phosphate with low impurity content in this example. As shown in Table 2 below, the impurity element content standards for iron phosphate for batteries and the impurity element content of the iron phosphate product in this example are provided.

[0072] Table 2

[0073]

[0074] Example 2

[0075] It is basically the same as Example 1, except that: Step S2: Heat the solution A to boiling, and after the volume of the solution is reduced to 60%, remove it from the heating device.

[0076] Example 3

[0077] It is basically the same as Example 1, except that: In Step S10, the above iron salt solution G, phosphate salt H, and hydrogen peroxide are fed in a molar ratio of Fe:P:H2O2 of 1:1:1.

[0078] Example 4

[0079] It is basically the same as Example 1, except that: In Step S10, the reaction temperature is 65°C and the reaction time is 1.8 h.

[0080] Example 5

[0081] It is basically the same as Example 1, except that: In Step S13, it is calcined at 600°C for 1.5 h.

[0082] Example 6

[0083] It is basically the same as Example 1, except that: In Step S13, it is calcined at 550°C for 2 h.

[0084] Comparative Example 1

[0085] It is basically the same as Example 1, except that: Steps S5 - S7 are cancelled, and the primary recrystallized iron salt crystal C prepared in Step S4 is used to replace crystal F in Step S8.

[0086] Comparative Example 2

[0087] It is basically the same as Example 1, except that: In Step S3, the stirring reaction time is replaced with 1 h.

[0088] Comparative Example 3

[0089] It is basically the same as Example 1, except that: In Step S1, the crude iron salt crystal is formulated into an iron salt solution with a total iron content of 120 g / L.

[0090] The purity parameters of the iron phosphate products obtained in each example and comparative example are provided as shown in Table 3 below.

[0091] Table 3

[0092]

[0093] As can be seen from the results in Table 3, by using the by-product ferrous sulfate crystals of titanium dioxide as the raw material in the embodiments of the present invention, iron phosphate products with low impurities can be prepared. High-content impurity elements such as Ca, Mg, Mn, Na, and Ti introduced based on titanium dioxide by-products are effectively removed, and their contents are reduced below the standard values, meeting the strict requirements for the impurity content of iron phosphate in the battery field.

[0094] Although the present invention has been illustrated and described with reference to specific embodiments, it should be realized that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; those of ordinary skill in the art should understand that: without departing from the spirit and scope of the present invention, the technical solutions recorded in the foregoing embodiments can be modified, or some or all of the technical features can be equivalently replaced; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention; therefore, this means that all such replacements and modifications within the scope of the present invention are included in the appended claims.

Claims

1. A method for preparing ferric phosphate, characterized in that: The steps include: (1) preparing a raw material liquid from ferrous sulfate crude salt which is a by-product of titanium dioxide production; (2) heating the raw material liquid to boiling and cooling it to obtain a mixed liquid; separating the mixed liquid into a solid and a liquid to obtain a recrystallized iron salt; (3) preparing the recrystallized iron salt into an iron salt solution, adjusting the pH of the iron salt solution to less than 1.80, and repeating step (2) to obtain a secondary crystallized iron salt; (4) preparing the secondary crystallized iron salt into a second iron salt solution; preparing a phosphate salt solution with monoammonium phosphate and ammonia water; The second iron salt solution, the phosphorus salt solution and hydrogen peroxide are mixed and reacted, and then the solid and liquid are separated to obtain an iron phosphate precursor; (5) The iron phosphate precursor is prepared into a precursor slurry, the pH value is adjusted to 1.6±0.2, and after it turns white, a temperature-raising reaction, solid-liquid separation and calcination are sequentially performed to obtain iron phosphate.

2. The method for preparing ferric phosphate according to claim 1, characterized in that: The total iron content of the crude ferrous sulfate salt is 12wt.% to 24wt.%; Preferably, the crude ferrous sulfate salt includes the following impurity components: Ca 20ppm-100ppm, Cd <10ppm, Cr <10ppm, Mg 2000ppm-4000ppm, Mn 400ppm-1500pm, Ni <50ppm, Pb <10ppm, Zn <100ppm, Al <100ppm, Ti <4180ppm.

3. The method for preparing ferric phosphate according to claim 1, characterized in that: In the raw material liquid, the total iron content is 80g / L to 100g / L; and / or, in the iron salt solution, the total iron content is 80 g / L to 100 g / L; And / or, in the second iron salt solution, the total iron content is 50 g / L to 70 g / L.

4. The method for preparing ferric phosphate according to claim 1, characterized in that: In step (2), during the heating to boiling, when the volume of the mixed solution decreases to 40% to 60%, the heating is stopped; Preferably, in step (2), for the cooling, the temperature is lowered at 20°C to 30°C for 2min to 4min, and then allowed to stand for 3h to 5h.

5. The method for preparing ferric phosphate according to claim 1, characterized in that: The preparation method of the phosphate solution comprises: The monoammonium phosphate is mixed with water, and then ammonia water is added until the pH value of the solution is 6.8 to 7.2 to obtain the phosphate solution; Preferably, the phosphorus content of the phosphate salt solution is 2.3 wt.% to 2.7 wt.%.

6. The method for preparing ferric phosphate according to claim 1, characterized in that: The molar ratio of the second iron salt solution, the phosphate salt solution and the hydrogen peroxide is 1:1:(0.75-1) based on the iron atoms of the second iron salt solution, the phosphorus atoms of the phosphate salt solution and the molecules of hydrogen peroxide in the hydrogen peroxide. Preferably, the temperature of the mixed reaction is 55°C to 65°C, and the time of the mixed reaction is 1.8h to 2h; Preferably, the temperature of the temperature-raising reaction is 80°C to 95°C, and the time of the temperature-raising reaction is 0.5h to 2h; Preferably, the calcination temperature is 550° C. to 600° C., and the calcination time is 1.5 h to 2.5 h.

7. A kind of iron phosphate, characterized in that: Prepared by the method for preparing iron phosphate according to any one of claims 1 to 6; Preferably, the purity of the ferric phosphate is ≥98%.

8. A lithium iron phosphate, characterized in that: The method is prepared by using the iron phosphate as claimed in claim 7.

9. A lithium ion battery, characterized in that: The method is prepared by using the iron phosphate as described in claim 7 or the lithium iron phosphate as described in claim 8.

10. An electrical device, characterized in that: Comprising the lithium ion battery as claimed in claim 9.

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