Hydrothermal method for preparing battery-grade iron phosphate by taking iron oxide as neutralizer and application of battery-grade iron phosphate

Abstract

The invention discloses a method for preparing battery-grade iron phosphate by using ferric oxide as a neutralizer through a hydrothermal method and application, and belongs to the field of batteries. The method comprises the following steps: S1, mixing ferric oxide, ferric trichloride, phosphoric acid and water, putting the mixture into a hydrothermal reaction kettle, and reacting to obtain a reaction product; and S2, carrying out solid-liquid separation on the reaction product to obtain a solid product, and calcining to obtain the battery-grade iron phosphate. According to the method, raw materials are prepared into a mixed solution with a certain concentration, ferric oxide is used as a neutralizer to neutralize acidity in a system, generation of ferric phosphate is promoted, and the method has the advantages of being simple in process, mild in reaction condition, high in product purity, environmentally friendly and the like and is suitable for preparing high-end battery-grade ferric phosphate.

Description

Technical Field

[0001] This invention relates to a method and application for preparing battery-grade iron phosphate using iron oxide as a neutralizing agent via a hydrothermal process, and belongs to the field of batteries. Background Technology

[0002] Iron phosphate, as an important precursor for lithium-ion battery cathode materials, can be prepared using various methods, such as precipitation, hydrothermal methods, and sol-gel methods. Among these, the hydrothermal method has attracted widespread attention due to its ability to achieve thorough mixing and reaction of reactants under high temperature and pressure, resulting in high-purity products with uniform particle size. However, traditional hydrothermal methods for preparing iron phosphate often require the use of large amounts of acid and alkali for adjustment, which not only increases production costs but also causes environmental pollution problems. Furthermore, the purity and particle size distribution of the product are difficult to control precisely. Summary of the Invention

[0003] The purpose of this invention is to provide a method for preparing battery-grade iron phosphate using iron oxide, ferric chloride, and phosphoric acid as main raw materials via a hydrothermal process, thereby solving the problems existing in the prior art.

[0004] According to the first aspect of this application, a method for preparing battery-grade iron phosphate using a hydrothermal process with iron oxide as a neutralizing agent is provided. This method uses iron oxide, ferric chloride, and phosphoric acid as main raw materials, avoiding the use of traditional iron sources such as ferrous sulfate and simplifying the raw material pretreatment process. Using iron oxide as a neutralizing agent neutralizes the acidity in the system, promoting the formation of iron phosphate, avoiding the use of neutralizing agents such as sodium hydroxide and potassium hydroxide, and preventing the introduction of impurity metal ions. The hydrothermal process, combined with the rotation of the hydrothermal reactor, achieves efficient synthesis of iron phosphate, resulting in a product with high purity and uniform particle size.

[0005] A method for preparing battery-grade iron phosphate using iron oxide as a neutralizing agent via a hydrothermal process, the method comprising the following steps:

[0006] S1 mixes iron oxide, ferric chloride, phosphoric acid and water, places them in a hydrothermal reactor, and reacts to obtain the reaction product;

[0007] S2 separates the reaction products into solid and liquid phases to obtain a solid product, which is then calcined to obtain battery-grade iron phosphate.

[0008] Optionally, in step S1, the molar ratio of iron oxide to ferric chloride is 1:1 to 8, and the molar ratio of iron to phosphate is 1:1 to 1.5.

[0009] Optionally, in step S1, the reaction temperature is 120℃~180℃, and the temperature is maintained for 2h~12h.

[0010] Optionally, in step S1, the temperature is increased to the reaction temperature at a heating rate of 2℃ / min to 10℃ / min.

[0011] Optionally, in step S1, the reaction is carried out under stirring at a speed of 10 rpm to 20 rpm.

[0012] Optionally, in step S2, the calcination temperature is 400℃~800℃ and the time is 2h~12h.

[0013] Optionally, in step S2, calcination is carried out in an air atmosphere.

[0014] In one preferred embodiment, the method includes the following steps:

[0015] (1) Raw material preparation: Prepare iron oxide (Fe2O3), ferric chloride (FeCl3) and phosphoric acid (H3PO4) as the main raw materials.

[0016] (2) Preparation of mixed solution: Add iron oxide, ferric chloride and phosphoric acid to a hydrothermal reactor, wherein the molar ratio of iron oxide to ferric chloride is 1:1 to 8, and the molar ratio of iron to phosphoric acid is 1:1 to 1.5. Add an appropriate amount of deionized water, and fill the reactor with liquid to no more than 2 / 3 of its volume. Stir evenly to obtain a mixed solution.

[0017] (3) Hydrothermal reaction: After the hydrothermal reactor is sealed, it is transferred to the internal rotatable high-temperature oven and fixed. It is rotated at 10 rpm to 20 rpm and heated to 120 ℃ to 180 ℃ at a heating rate of 2 ℃ / min to 10 ℃ / min, and kept for 2 h to 12 h.

[0018] (4) Product processing: After the reaction is complete, the mixture is allowed to cool naturally to room temperature. The reaction vessel is then opened to obtain the reaction product. The reaction product is subjected to solid-liquid separation to obtain a solid product and a mother liquor. The solid product is washed three times with deionized water and dried to obtain hydrated ferric phosphate. The hydrated ferric phosphate is then calcined in an air atmosphere at a temperature of 400℃~800℃ for 2h~12h to obtain battery-grade ferric phosphate.

[0019] According to a second aspect of this application, an application of battery-grade iron phosphate prepared by a hydrothermal method using iron oxide as a neutralizing agent is provided.

[0020] Application of battery-grade iron phosphate prepared by the above method in battery materials.

[0021] Compared with the prior art, the present invention has the following beneficial effects:

[0022] This invention provides a hydrothermal method for preparing battery-grade iron phosphate using iron oxide as a neutralizing agent. The method uses iron oxide, ferric chloride, and phosphoric acid as main raw materials and employs a hydrothermal process. This method prepares the raw materials into a mixed solution of a certain concentration, utilizes iron oxide as a neutralizing agent to neutralize the acidity in the system, and promotes the formation of iron phosphate. It has advantages such as simple process, mild reaction conditions, high product purity, and environmental friendliness, and is suitable for preparing high-end battery-grade iron phosphate. Attached Figure Description

[0023] Figure 1 The image shows the SEM image of hydrated iron phosphate obtained in Example 1.

[0024] Figure 2 The image shows the XRD pattern of hydrated iron phosphate obtained in Example 1.

[0025] Figure 3 The image shows a SEM image of the battery-grade iron phosphate obtained in Example 1.

[0026] Figure 4 The image shows the XRD pattern of battery-grade iron phosphate obtained in Example 1. Detailed Implementation

[0027] The present application is described in detail below with reference to the embodiments, but the present application is not limited to these embodiments.

[0028] Unless otherwise specified, all raw materials used in the embodiments of this application were purchased through commercial channels.

[0029] Unless otherwise specified, all test methods are standard and all instrument settings are those recommended by the manufacturer.

[0030] The analysis method in the embodiments of this application is as follows:

[0031] The scanning electron microscopy (SEM) analysis was performed using a SU-8010 field emission scanning electron microscope with an elemental analysis probe.

[0032] The instrument used for phase structure (XRD) analysis was MiniFlex II.

[0033] Example 1

[0034] 1) Raw material preparation: 15.97g of iron oxide (Fe2O3), 54.06g of ferric chloride hexahydrate (FeCl3·6H2O), and 55.34g of 85% phosphoric acid.

[0035] 2) Preparation of the mixed solution: Add ferric oxide, ferric chloride, and phosphoric acid to a hydrothermal reactor, wherein the molar ratio of ferric oxide to ferric chloride is 1:2, and the molar ratio of iron to phosphoric acid is 1:1.2. Add 200 mL of deionized water, select a 300 mL hydrothermal reactor, and fill the reactor to no more than 2 / 3 of its volume with liquid. Stir well to obtain a mixed solution.

[0036] 3) Hydrothermal reaction: After the hydrothermal reactor is sealed, it is transferred to the internal rotatable high-temperature oven and fixed. It is rotated at 10 rpm and heated to 120°C at a heating rate of 2°C / min, and held for 12 hours.

[0037] 4) Product Processing: After the reaction is complete, allow it to cool naturally to room temperature. Open the reactor to obtain the reaction product. Separate the reaction product into solid and liquid components to obtain a solid product and mother liquor. Wash the solid product three times with deionized water and dry it to obtain hydrated ferric phosphate. Calcine the hydrated ferric phosphate in an air atmosphere at 800℃ for 2 hours to obtain battery-grade ferric phosphate.

[0038] Example 2

[0039] 1) Raw material preparation: 15.97g of iron oxide (Fe2O3), 27.03g of ferric chloride hexahydrate (FeCl3·6H2O), and 41.50g of 85% phosphoric acid.

[0040] 2) Preparation of the mixed solution: Add ferric oxide, ferric chloride, and phosphoric acid to a hydrothermal reactor, wherein the molar ratio of ferric oxide to ferric chloride is 1:1, and the molar ratio of iron to phosphoric acid is 1:1.2. Add 200 mL of deionized water, select a 300 mL hydrothermal reactor, and fill the reactor to no more than 2 / 3 of its volume with liquid. Stir well to obtain a mixed solution.

[0041] 3) Hydrothermal reaction: After the hydrothermal reactor is sealed, it is transferred to the internal rotatable high-temperature oven and fixed. It is rotated at 10 rpm and heated to 180°C at a heating rate of 2°C / min, and held for 12 hours.

[0042] 4) Product Processing: After the reaction is complete, allow it to cool naturally to room temperature. Open the reactor to obtain the reaction product. Separate the reaction product into solid and liquid components to obtain a solid product and mother liquor. Wash the solid product three times with deionized water and dry it to obtain hydrated ferric phosphate. Calcine the hydrated ferric phosphate in an air atmosphere at 800℃ for 2 hours to obtain battery-grade ferric phosphate.

[0043] Examples 3-5

[0044] The operation is the same as in Example 1, except that the hydrothermal reaction temperature is changed to 130°C, 140°C and 150°C to obtain battery-grade iron phosphate.

[0045] Examples 6-8

[0046] The operation is the same as in Example 1, except that the calcination temperature is changed to 400°C, 500°C and 600°C to obtain battery-grade iron phosphate.

[0047] Characterization tests:

[0048] Taking Example 1 as an example, Figure 1 This is a SEM image of hydrated iron phosphate obtained in Example 1. Figure 3 The image shown is a SEM image of the battery-grade iron phosphate obtained in Example 1. The precursor hydrated iron phosphate mainly has a lamellar structure, and the product still retains the lamellar structure after calcination.

[0049] Figure 2 The XRD pattern of hydrated iron phosphate obtained in Example 1 is shown below. Figure 4 The image shows the XRD pattern of battery-grade iron phosphate obtained in Example 1. The hydrated iron phosphate has high phase purity and fully developed crystals. After calcination, the product is completely converted into iron phosphate.

[0050] The above description is merely a few embodiments of this application and is not intended to limit this application in any way. Although this application discloses preferred embodiments as described above, it is not intended to limit this application. Any changes or modifications made by those skilled in the art without departing from the scope of the technical solution of this application using the disclosed technical content are equivalent to equivalent implementation cases and fall within the scope of the technical solution.

Claims

1. A method for preparing battery-grade iron phosphate via a hydrothermal process using iron oxide as a neutralizing agent, characterized in that, The method includes the following steps: S1 mixes iron oxide, ferric chloride, phosphoric acid and water, places them in a hydrothermal reactor, and reacts to obtain the reaction product; S2 separates the reaction products into solid and liquid phases to obtain a solid product, which is then calcined to obtain battery-grade iron phosphate.

2. The method according to claim 1, characterized in that, In step S1, the molar ratio of iron oxide to ferric chloride is 1:1 to 8, and the molar ratio of iron to phosphate is 1:1 to 1.

5.

3. The method according to claim 1, characterized in that, In step S1, the reaction temperature is 120℃~180℃, and the temperature is maintained for 2h~12h.

4. The method according to claim 3, characterized in that, In step S1, the temperature is increased to the reaction temperature at a heating rate of 2℃ / min to 10℃ / min.

5. The method according to claim 1, characterized in that, In step S1, the reaction is carried out under rotary stirring at a speed of 10 rpm to 20 rpm.

6. The method according to claim 1, characterized in that, In step S2, the calcination temperature is 400℃~800℃, and the time is 2h~12h.

7. The method according to claim 1, characterized in that, In step S2, calcination is carried out in an air atmosphere.

8. The application of battery-grade iron phosphate prepared by the method according to any one of claims 1 to 7 in battery materials.

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