Iron phosphate material, and preparation method therefor and use thereof

Abstract

An iron phosphate material, and a preparation method therefor and the use thereof. In the preparation method for the iron phosphate material, by introducing acetone and C3-C5 alkyl diamines into the reaction process and performing three stages of reactions, the prepared iron phosphate material has a relatively small particle size, a high compaction density, a large specific surface area and a high purity. The preparation method is simple to operate and is thus conducive to actual production.

Description

A kind of iron phosphate material and its preparation method and application Technical Field

[0001] The present disclosure belongs to the technical field of positive electrode materials, and in particular relates to an iron phosphate material and a preparation method and application thereof. Background Art

[0002] The most commonly used positive electrode materials in lithium batteries are lithium iron phosphate and ternary materials. Among them, lithium iron phosphate (LFP) material has become a lithium-ion battery positive electrode material with great application potential due to its advantages such as low cost, good high-temperature performance, large capacity, no memory effect, light weight, and environmental protection. Iron phosphate is an important precursor for the preparation of lithium iron phosphate. Its chemical composition, structure, physicochemical properties, and reactivity largely determine the overall performance of the resulting lithium iron phosphate positive electrode material. Currently, the main methods for preparing iron phosphate include hydrothermal method, sol-gel method, homogeneous precipitation method, and microwave method. These methods have their own advantages and disadvantages. Currently, common problems with existing preparation methods include: a large number of side reactions during the preparation process, a high level of impurities in the produced iron phosphate, low product purity, large primary particle size, small specific surface area, and low compaction density, which affect the performance of the lithium iron phosphate positive electrode material prepared later.

[0003] Summary of the Invention

[0004] The purpose of the present disclosure is to overcome the deficiencies of the above-mentioned prior art and to provide an iron phosphate material with smaller particle size, higher compaction density, larger specific surface area and higher purity, as well as a preparation method and application thereof.

[0005] To achieve the above objectives, in a first aspect of the present disclosure, the present disclosure provides a method for preparing an iron phosphate material, the preparation method comprising the following steps:

[0006] Dissolve the iron salt in an acetone aqueous solution and then add C3-5 alkyl diamine to obtain an iron salt solution;

[0007] After adding the phosphorus source solution to the iron salt solution, a first reaction is carried out. After the first reaction, the temperature is increased at a first rate to carry out a second reaction. After the second reaction, the temperature is increased at a second rate to carry out a third reaction. After the third reaction, the mixture is centrifuged, the precipitate is collected, washed, and dried to obtain an intermediate product.

[0008] The intermediate product is calcined to obtain iron phosphate material.

[0009] The preparation method of the iron phosphate material provided by the present disclosure introduces acetone and C3-C5 alkyl diamine during the reaction process and performs a three-stage reaction; so that the prepared iron phosphate material has a small particle size, high compaction density, large specific surface area, and high purity.

[0010] Specifically, the introduction of C3-C5 alkyl diamine, the nitrogen atom on the amine has a pair of lone electron pairs, and the iron ion has an empty orbital to accept electrons, and the two can form a complex system. C3-C5 alkyl diamine complexes part of the iron ions to regulate the generation rate of iron phosphate. C3-C5 alkyl diamine can also control the growth direction of FePO4, thereby controlling the particle size, uniformity and specific surface area of ​​the generated iron phosphate. Acetone is added during the preparation process. First, acetone can be added as a solvent to enhance the dispersibility of iron ions. Second, the oxygen atoms in the acetone molecules also have lone electron pairs, which can form a complex with iron ions. That is, the oxygen atoms in acetone will participate in the coordination of iron ions with the nitrogen atoms in C3-C5 alkyl diamine at the same time, thereby further regulating the generation rate of iron phosphate, so that the particle size distribution of the product is concentrated, with good consistency and large specific surface area. Third, acetone is volatile, and with the subsequent three-stage programmed reaction, it can further regulate the reaction generation rate. Among them, the first reaction mainly utilizes acetone and C3-C5 alkyl diamine to complex part of the iron ions. ions and form a competitive relationship, slowly reacting to generate nano-iron phosphate; the second and third reactions gradually increase the temperature at a certain heating rate to volatilize the acetone, at this time the complex concentration of the C=O bond and the iron ion in the acetone decreases, releasing more iron ions, and at the same time the particles tend to aggregate, promoting the forward reaction of the iron ions and the phosphate radical, and finally the acetone in the solution is completely volatilized, and the reaction is further promoted by regulating the temperature to complete the final reaction, so that the obtained iron phosphate has a high compaction density; in addition, the slow iron phosphate generation process can also reduce the impurity ions in the product, prevent the impurities adsorbed on the surface from remaining in the product due to too fast precipitation, thereby improving the purity of the final iron phosphate material.

[0011] In one embodiment, the C3-5 alkyl diamine includes at least one of 1,2-propylene diamine and 1,4-butanediamine.

[0012] In one embodiment, the C3-5 alkyl diamine is 1,2-propylene diamine.

[0013] The present disclosure study found that when the C3-5 alkyl diamine is further selected as 1,2-propylene diamine, it can better complex with iron ions, thereby regulating the generation rate of iron phosphate and obtaining a product with smaller particle size and larger specific surface area.

[0014] In one embodiment, the volume ratio of acetone, water and C3-5 alkyl diamine is acetone:water:C3-5 alkyl diamine=(0.5-1):1:(0.5-1).

[0015] The present disclosure study found that when the volume ratio of acetone, water and C3-5 alkyl diamine in the acetone aqueous solution is further selected to be (0.5-1):1:(0.5-1), acetone and C3-5 alkyl diamine have a better synergistic effect in reducing the ferric phosphate formation rate, thereby making the particle size of the ferric phosphate material smaller and the particle size distribution more uniform.

[0016] In one embodiment, rapid stirring is maintained when adding the C3-5 alkyl diamine, with a stirring speed of 700-900 rpm.

[0017] In one embodiment, the C3-5 alkyl diamine is added dropwise at a rate of 0.5-1.5 mL / min. In one embodiment, the phosphorus source solution is stirred at a rate of 300-600 rpm while being added.

[0018] In one embodiment, the phosphorus source solution is added dropwise at a rate of 4-6 mL / min.

[0019] In one embodiment, the mass-to-volume ratio of the iron salt to the acetone aqueous solution is 1 g:(3-5) mL.

[0020] The present disclosure found that a suitable mass-to-volume ratio of iron salt to acetone aqueous solution can make the concentration in the reaction system moderate, thereby improving the particle specific surface area and purity of the reaction product.

[0021] In one embodiment, the iron salt includes at least one of ferric sulfate and its hydrate, ferric chloride and its hydrate, and ferric nitrate and its hydrate.

[0022] In one embodiment, the phosphorus source includes at least one of phosphoric acid and phosphate.

[0023] In one embodiment, the molar ratio of iron in the iron salt to phosphorus in the phosphorus source is 1:1.

[0024] In one embodiment, the phosphorus source solution is an aqueous solution of a phosphorus source; in the phosphorus source solution, the mass percentage of the phosphorus source is 10-30%.

[0025] In one embodiment, the temperature of the first reaction is 20-30° C., and the time of the first reaction is 0.5-1.5 h.

[0026] In one embodiment, the temperature of the second reaction is 70-80° C., and the time of the second reaction is 0.5-1.5 h.

[0027] In one embodiment, the temperature of the third reaction is 100-110° C., and the time of the third reaction is 1.5-2.5 hours.

[0028] In one embodiment, the first heating rate and the second heating rate are each independently 3-5° C. / min.

[0029] In one embodiment, the duration ratio of the first reaction time, the second reaction time, and the third reaction time is first reaction time: second reaction time: third reaction time=1:(1-2):(2-3).

[0030] The present disclosure found that the selection of reaction temperature and time for the three stages and the selection of heating rate for the last two stages can not only help improve the specific surface area of ​​the product, but also improve the compacted density and purity of the product; specifically, the first stage reacts at 20-30°C, mainly using acetone and C3-5 alkyl diamine to complex part of the iron ions and form a competitive relationship, slowly reacting to generate nano-iron phosphate; then the temperature is increased at a certain heating rate, and the acetone will slowly evaporate during the heating process. At this time, the complex concentration of the C=O bond in the acetone and the iron ions decreases, releasing more iron ions. At the same time, the particles tend to aggregate, promoting the forward reaction of the iron ions and phosphate, and finally the acetone in the solution is completely evaporated; then the temperature is controlled by slowly increasing the temperature to further promote the reaction and complete the final reaction.

[0031] In one embodiment, the washing is performed using anhydrous ethanol and deionized water.

[0032] In one embodiment, the calcination temperature is 500-650° C., and the calcination time is 2-4 hours.

[0033] In one embodiment, the calcination is carried out in an inert gas environment; the inert gas includes at least one of nitrogen and a rare gas.

[0034] In a second aspect of the present disclosure, the present disclosure provides an iron phosphate material, which is prepared using the preparation method described in the present disclosure.

[0035] The particle size of the iron phosphate material prepared in the present invention is between 321-394 nm, and the specific surface area is 16.13 m 2 / g or above, compacted density is 2.29g / cm 3 Above, the content of sulfur peroxide in the product is below 45ppm.

[0036] In a third aspect of the present disclosure, the present disclosure provides a use of the iron phosphate material in preparing a positive electrode material.

[0037] Compared with the prior art, the present invention has the following beneficial effects:

[0038] The present invention provides a method for preparing an iron phosphate material. By introducing acetone and a C3-C5 alkyl diamine during the reaction process and conducting a three-stage reaction, the prepared iron phosphate material has a small particle size, a large specific surface area, a high compacted density, and high purity. Furthermore, the method is simple to operate, facilitating practical production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] FIG1 is a SEM image of the iron phosphate material prepared in Example 1. DETAILED DESCRIPTION

[0040] In order to better illustrate the purpose, technical solutions and advantages of the present disclosure, the present disclosure will be further described below in conjunction with specific embodiments.

[0041] Unless otherwise specified, the reagents, methods and equipment used in the present disclosure are conventional reagents, methods and equipment in the art.

[0042] Example 1

[0043] The present disclosure provides an iron phosphate material, and a method for preparing the iron phosphate material includes the following steps:

[0044] (1) Mix 5 mL of acetone and 10 mL of deionized water, then add 4.00 g of ferric sulfate and stir evenly. Then, add 10 mL of 1,2-propylenediamine (the volume ratio of acetone, deionized water and 1,2-propylenediamine is 0.5:1:1) dropwise at a stirring speed of 700 rpm and a rate of 1 mL / min. After the addition is complete, stir for 30 minutes to obtain an iron salt solution.

[0045] (2) adding a phosphoric acid aqueous solution (the mass percentage of phosphoric acid in the phosphoric acid aqueous solution is 20%) to the iron salt solution at a rate of 5 mL / min while stirring at a speed of 500 rpm, wherein the molar ratio of phosphorus in the phosphoric acid solution to iron in the iron salt solution is 1:1;

[0046] (3) After the dropwise addition is completed, the first reaction is carried out at 25°C for 1 hour. After the first reaction is completed, the temperature is raised to 70°C at a heating rate of 3°C / min for a second reaction. The second reaction is carried out for 1 hour. After the second reaction is completed, the temperature is raised to 100°C at a heating rate of 3°C / min for a third reaction. The third reaction is carried out for 2 hours. After the third reaction is completed, the mixture is cooled to room temperature and centrifuged. The precipitate is collected and washed three times with anhydrous ethanol and deionized water. After washing, the mixture is dried at 80°C to obtain an intermediate product.

[0047] (4) The intermediate product is placed under inert gas protection, calcined at 560° C. for 3 h, and cooled after calcination to obtain an iron phosphate material.

[0048] Example 2

[0049] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and embodiment 1 is that in step (1), the volume ratio of acetone, deionized water and 1,2-propylenediamine is 1:1:1.

[0050] Example 3

[0051] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and embodiment 1 is that in step (1), the volume ratio of acetone, deionized water and 1,2-propylenediamine is 1:1:0.5.

[0052] Example 4

[0053] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and embodiment 1 is that in step (1), the volume ratio of acetone, deionized water and 1,2-propylenediamine is 0.5:1:0.1.

[0054] Example 5

[0055] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and embodiment 1 is that in step (1), the volume ratio of acetone, deionized water and 1,2-propylenediamine is 0.5:1:2.

[0056] Example 6

[0057] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and embodiment 1 is that in step (1), 1,4-butanediamine is used instead of 1,2-propylenediamine.

[0058] Example 7

[0059] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and the embodiment 1 is in step (3). Step (3) of the embodiment is:

[0060] After the dropwise addition is completed, the first reaction is carried out at 30°C for 1 hour. After the first reaction is completed, the temperature is raised to 80°C at a heating rate of 5°C / min for the second reaction. The second reaction time is 1 hour. After the second reaction is completed, the temperature is raised to 110°C at a heating rate of 5°C / min for the third reaction. The third reaction time is 2 hours. After the third reaction is completed, it is cooled to room temperature and centrifuged. The precipitate is collected and washed 3 times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0061] Example 8

[0062] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and the embodiment 1 is in step (3). Step (3) of the embodiment is:

[0063] After the dropwise addition is completed, the first reaction is carried out at 35°C for 1 hour. After the first reaction is completed, the temperature is increased to 90°C at a heating rate of 3°C / min for the second reaction. The second reaction time is 1 hour. After the second reaction is completed, the temperature is increased to 120°C at a heating rate of 3°C / min for the third reaction. The third reaction time is 2 hours. After the third reaction is completed, it is cooled to room temperature and centrifuged. The precipitate is collected and washed 3 times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0064] Example 9

[0065] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and the embodiment 1 is in step (3). Step (3) of the embodiment is:

[0066] After the dropwise addition is completed, the first reaction is carried out at 15°C for 1 hour. After the first reaction is completed, the temperature is raised to 60°C at a heating rate of 3°C / min for a second reaction. The second reaction time is 1 hour. After the second reaction is completed, the temperature is raised to 90°C at a heating rate of 3°C / min for a third reaction. The third reaction time is 2 hours. After the third reaction is completed, it is cooled to room temperature and centrifuged. The precipitate is collected and washed 3 times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0067] Example 10

[0068] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and the embodiment 1 is in step (3). Step (3) of the embodiment is:

[0069] After the dropwise addition is completed, the first reaction is carried out at 25°C for 1 hour. After the first reaction is completed, the temperature is raised to 70°C at a heating rate of 8°C / min for the second reaction. The second reaction time is 1 hour. After the second reaction is completed, the temperature is raised to 100°C at a heating rate of 8°C / min for the third reaction. The third reaction time is 2 hours. After the third reaction is completed, it is cooled to room temperature and centrifuged. The precipitate is collected and washed 3 times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0070] Example 11

[0071] The embodiment of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and the embodiment 1 is in step (3). Step (3) of the embodiment is:

[0072] After the dropwise addition is completed, the first reaction is carried out at 25°C for 1 hour. After the first reaction is completed, the temperature is raised to 70°C at a heating rate of 1°C / min for a second reaction. The second reaction time is 1 hour. After the second reaction is completed, the temperature is raised to 100°C at a heating rate of 1°C / min for a third reaction. The third reaction time is 2 hours. After the third reaction is completed, it is cooled to room temperature and centrifuged. The precipitate is collected and washed 3 times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0073] Example 12

[0074] An embodiment of the present disclosure provides an iron phosphate material, the only difference between the iron phosphate material and Example 1 is that in step (3), the time of the first reaction: the time of the second reaction: the time of the third reaction = 1:2:3, and the total duration of the first reaction time, the second reaction time and the third reaction time remains unchanged at 4 hours.

[0075] Example 13

[0076] The embodiment of the present disclosure provides an iron phosphate material, the only difference between the iron phosphate material and Example 1 is that in step (3), the time of the first reaction: the time of the second reaction: the time of the third reaction = 0.5:1:2, and the total duration of the first reaction time, the second reaction time and the third reaction time remains unchanged at 4 hours.

[0077] Example 14

[0078] The embodiment of the present disclosure provides an iron phosphate material, the only difference between the iron phosphate material and Example 1 is that in step (3), the time of the first reaction: the time of the second reaction: the time of the third reaction = 1.5:1:2, and the total duration of the first reaction time, the second reaction time and the third reaction time remains unchanged at 4h.

[0079] Comparative Example 1

[0080] The comparative example of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and Example 1 is that acetone is not added in step (1), and the volume of acetone is supplemented with deionized water and 1,2-propylenediamine, that is, the volume ratio of deionized water and 1,2-propylenediamine is 1:1, and the total volume of the two is 25 mL.

[0081] Comparative Example 2

[0082] The comparative example of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and Example 1 is that 1,2-propylenediamine is not added in step (1), and the volume of 1,2-propylenediamine is supplemented with acetone aqueous solution, that is, the acetone aqueous solution is 25 mL in total, and the volume of acetone and deionized water is 0.5:1.

[0083] Comparative Example 3

[0084] The comparative example of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and Example 1 is step (3). Step (3) of this comparative example is:

[0085] After the dropwise addition is completed, the first reaction is carried out at 25°C for 1 hour. After the first reaction is completed, the temperature is increased to 100°C at a heating rate of 3°C / min for a second reaction. The second reaction time is 3 hours. After the second reaction is completed, it is cooled to room temperature and centrifuged. The precipitate is collected and washed three times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0086] Comparative Example 4

[0087] The comparative example of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and Example 1 is step (3). Step (3) of this comparative example is:

[0088] After the dropwise addition is completed, the first reaction is carried out at 25°C for 1 hour. After the first reaction is completed, the temperature is raised to 70°C at a heating rate of 3°C / min for a second reaction. The second reaction time is 3 hours. After the second reaction is completed, it is cooled to room temperature and centrifuged, and the precipitate is collected and washed three times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0089] Comparative Example 5

[0090] The comparative example of the present disclosure provides an iron phosphate material. The only difference between the iron phosphate material and Example 1 is step (3). Step (3) of this comparative example is:

[0091] After the dropwise addition is completed, the temperature is first raised to 70°C at a heating rate of 3°C / min for a first reaction, and the first reaction time is 2 hours. After the first reaction is completed, the temperature is raised to 100°C at a heating rate of 3°C / min for a second reaction, and the second reaction time is 2 hours. After the second reaction is completed, it is cooled to room temperature and centrifuged, and the precipitate is collected and washed three times with anhydrous ethanol and deionized water. After washing, it is dried at 80°C to obtain an intermediate product.

[0092] Effect Examples

[0093] The particle size, specific surface area, compacted density and sulfate content of the iron phosphate materials prepared in Examples 1-14 and Comparative Examples 1-5 were tested in the present disclosure, wherein the particle size was tested using a laser particle size analyzer; the compacted density was tested using a compacted density meter, the specific surface area was tested using the BET test method, and the sulfate content was tested using ICP-OES; the results obtained are shown in Table 1; in addition, the SEM image of the iron phosphate material prepared in Example 1 is shown in Figure 1, from which it can be seen that the prepared iron phosphate has no obvious agglomeration and good dispersibility;

[0094] Table 1

[0095] As can be seen from Table 1, the phosphoric acid material prepared by the technical solution of the present disclosure has a smaller particle size and a larger specific surface area, and also has a higher compaction density and purity. Specifically, the compaction density of the obtained product is 2.29 g / cm 3 Above, the particle size is between 321-394nm, and the specific surface area is 16.13m 2 / g or more, and the sulfur peroxide content is below 45ppm;

[0096] It can be seen from Examples 1-5 that the volume ratio of acetone, deionized water, and 1,2-propylene diamine added will affect the performance of the product. When the volume ratio of acetone, deionized water, and 1,2-propylene diamine is further preferably (0.5-1):1:(1-2), the comprehensive performance of the obtained product is better, wherein the compacted density is 2.35 g / cm 3 Above, the specific surface area is 21.63m 2 / g or more, and the sulfur peroxide content is below 18ppm;

[0097] It can be seen from Example 1 and Examples 7-11 that the temperature and heating rate of the three reaction stages during the reaction process will affect the overall performance of the product; it can be seen from Example 1 and Examples 12-14 that the reaction time ratio of the three reaction stages will also affect the overall performance of the product;

[0098] It can be seen from Example 1 and Comparative Examples 1-2 that acetone and C3-5 alkyl diamine are indispensable. Regardless of whether either of them is added, the compacted density of the obtained product is significantly reduced, the sulfur peroxide content is significantly increased, and the particle size distribution uniformity of the product is also significantly reduced. Compared with Example 1, the compacted density of Comparative Examples 1-2 decreased by 11.11-12.76%, the sulfur peroxide content increased by 238.89-316.67%, and the specific surface area decreased by 35.38-38.88%.

[0099] It can be seen from Example 1 and Comparative Examples 3-5 that the three-stage reaction is indispensable. If any one of the reaction stages is missing, the performance of the obtained product will be significantly reduced. Compared with Example 1, the compacted density of Comparative Examples 1-2 decreased by 6.58-8.23%, the sulfur peroxide content increased by 150.00-188.89%, and the specific surface area decreased by 31.06-32.40%.

Claims

1. A method for preparing a lithium iron phosphate material, characterized in that, The preparation method comprises the following steps: Dissolve an iron salt in an aqueous acetone solution, and then add a C3-5 alkylenediamine to obtain an iron salt solution; Add a phosphorus source solution to the iron salt solution and conduct a first reaction. After the first reaction ends, raise the temperature at a first rate to conduct a second reaction. After the second reaction ends, raise the temperature at a second heating rate to conduct a third reaction. After the third reaction ends, centrifuge, collect the precipitate, wash, and dry to obtain an intermediate product; Calcine the intermediate product to obtain an iron phosphate material.

2. The preparation method according to claim 1, characterized in that, The C3-5 alkylenediamine includes at least one of 1,2-propanediamine and 1,4-butanediamine.

3. The preparation method according to claim 1, wherein The volume ratio of acetone, water, and C3-5 alkylenediamine is acetone: water: C3-5 alkylenediamine = (0.5-1): 1: (0.5-1).

4. The preparation method according to claim 1, wherein The mass-volume ratio of the iron salt to the aqueous acetone solution is 1 g: (3-5) mL.

5. The preparation method according to claim 1, characterized in that, The iron salt includes at least one of iron sulfate and its hydrate, iron chloride and its hydrate, and iron nitrate and its hydrate.

6. The preparation method according to claim 1, characterized in that, The phosphorus source includes at least one of phosphoric acid and phosphate.

7. The preparation method according to claim 1, characterized in that The molar ratio of iron in the iron salt to phosphorus in the phosphorus source is 1:

1.

8. The preparation method according to claim 1, wherein The temperature of the first reaction is 20-30 °C, and the time of the first reaction is 0.5-1.5 h.

9. The preparation method according to claim 1, characterized in that, The temperature of the second reaction is 70-80 °C, and the time of the second reaction is 0.5-1.5 h.

10. The preparation method according to claim 1, characterized in that, The temperature of the third reaction is 100-110 °C, and the time of the third reaction is 1.5-2.5 h.

11. According to the preparation method described in claim 1, characterized in that, The first heating rate and the second heating rate are each independently 3-5 °C / min.

12. The preparation method according to claim 1, wherein The duration ratio of the time of the first reaction, the time of the second reaction, and the time of the third reaction is the time of the first reaction: the time of the second reaction: the time of the third reaction = 1: (1-2): (2-3).

13. According to the preparation method described in claim 1, characterized in that, The calcination temperature is 500-650 °C, and the calcination time is 2-4 h.

14. A lithium iron phosphate material, characterized in that, The iron phosphate material is prepared by using the preparation method described in any one of claims 1-13.

15. Use of the iron phosphate material according to claim 14 in the preparation of a cathode material.

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