A method for preparing battery-grade iron phosphate

Abstract

The application discloses a preparation method of battery-grade iron phosphate, which comprises the following steps: (1) preparing iron hydroxide powder and phosphoric acid; (2) diluting the phosphoric acid into a phosphoric acid solution by using deionized water, and then stirring the iron hydroxide and the phosphoric acid solution in a reactor; (3) after sufficient stirring, a catalyst is added, and a dispersing agent and a crystal transformation inducer are added within 30-40 minutes after the reaction starts, and the reaction is heated; (4) after the heating reaction is completed, the precipitate is separated out, and then the separated precipitate is washed and dried, and after drying, the precipitate is crushed and screened, so as to obtain the prepared iron phosphate. The preparation method is simple and easy to implement, does not need a large number of equipment and a complex technological process, can be used for large-scale production, has good economic benefits, and can meet the use requirements in the field of new energy batteries, and the prepared product is stable in quality, excellent in quality, and can be prepared in a short time.

Description

Technical Field

[0001] This invention relates to the field of iron phosphate synthesis technology, and more particularly to a method for preparing battery-grade iron phosphate. Background Technology

[0002] Ferric phosphate is an important inorganic compound widely used in the manufacture of steel, ferrites, catalysts, and new energy sources. Currently, the main methods for preparing ferric phosphate include hydrothermal methods, gelation methods, and high-temperature drying methods. However, these methods all suffer from long preparation cycles, complex processes, and high costs. Therefore, a simpler, more practical, and economical preparation method is needed.

[0003] CN112758909A discloses a high-speed iron method for producing battery-grade iron phosphate. First, high-purity iron is reacted with nitric acid to prepare iron nitrate, which is then mixed with phosphoric acid and heated. A certain proportion of iron phosphate inducer is added to prepare iron phosphate. This method is costly and the product quality is unstable. Summary of the Invention

[0004] This invention provides a method for preparing battery-grade iron phosphate to solve the problems of long preparation cycle, complex process and high cost in the existing iron phosphate preparation methods mentioned above.

[0005] The solution of the present invention is:

[0006] A method for preparing battery-grade iron phosphate includes the following steps:

[0007] (1) Prepare ferric hydroxide powder and phosphoric acid;

[0008] (2) Dilute phosphoric acid with deionized water to form a phosphoric acid solution, and then add ferric hydroxide and the phosphoric acid solution into the reactor and stir.

[0009] (3) After stirring thoroughly, add the catalyst. Add the dispersant and crystallization inducer within 30 to 40 minutes after the start of the reaction and heat the reaction.

[0010] (4) After the heating reaction is complete, the precipitate is separated, and then the separated precipitate is washed and dried. After drying, it is crushed and screened to obtain the prepared iron phosphate.

[0011] Ferric hydroxide powder was selected as the iron source and phosphoric acid solution as the phosphorus source. The synthesis mechanism is acid-base neutralization, which makes it easier to convert to high-purity ferric phosphate during the preparation process, thereby reducing the impurity content. The catalyst is used to provide the optimal pH of 1.5-2.5 for product crystal growth during the reaction synthesis. The crystal growth induction agent can induce the crystal growth of the material during the synthesis process, thereby obtaining ferric phosphate products with excellent crystallinity and uniform particle distribution. This facilitates the improvement of the stability of the electrical performance of the product when applied to battery materials. The process is simple, easy to implement, and economically efficient. The product prepared by this process has good crystallinity, is plate-like, and has small primary particle crystals at the nanoscale.

[0012] As a preferred technical solution, in (1), the mass fractions of ferric hydroxide powder and phosphoric acid are 105-110 parts of ferric hydroxide and 115-120 parts of phosphoric acid, respectively.

[0013] As a preferred technical solution, the concentration of phosphoric acid in (1) is 85%.

[0014] As a preferred technical solution, the mass fraction of deionized water added in (2) is 530 to 545 parts.

[0015] As a preferred technical solution, the catalyst in (3) is one or both of sodium hydroxide and ammonia solution, and the amount of catalyst added is 1-2% of the total reaction liquid weight, adjusting the pH to 1.5-2.5. Sodium hydroxide or ammonia solution is used as a catalyst because it is inexpensive and produces only a single byproduct, while also providing a suitable crystal growth environment for iron phosphate.

[0016] As a preferred technical solution, a dispersant is added simultaneously with the catalyst in step 3), and the amount of dispersant added is 1-2‰ of the total reaction liquid weight. Adding a dispersant at this point can make the crystal particles more uniform, which is more conducive to the formation of crystals after the inducing agent is added in the subsequent process, thereby improving the crystallization conversion rate. The dispersant is an anionic surfactant, and the anionic surfactant is sodium dodecyl sulfate.

[0017] As a preferred technical solution, the crystal transformation inducing agent in (3) is the standard reagent ferric phosphate. Ferric phosphate crystals will be formed in the early stage of the reaction, but at this time the ferric phosphate crystals are in the form of unit cells. Therefore, if the crystal inducing agent is added directly at this time, the amount of unit cells is insufficient, and only the generated unit cells can be induced to transform into plate-shaped ferric phosphate crystals. Excessive crystal inducing agent will be consumed in other reactions, resulting in waste of raw materials. Therefore, the crystal inducing agent is added during the period of 30-40 minutes. The number of unit cells generated during this period is sufficient to fully induce the reaction. If it is added after 40 minutes, some of the cellular ferric phosphate crystals will transform into other forms of crystals, which will affect the quality of the final product. This invention can obtain plate-shaped ferric phosphate crystals of better quality.

[0018] As a preferred technical solution, the amount of standard reagent ferric phosphate added in (3) is 1 to 5‰ of the total weight of the reaction solution.

[0019] As a preferred technical solution, the heating reaction conditions in (3) are 200-300°C for 4-12 hours.

[0020] As a preferred technical solution, after the heating reaction in step (4) is completed, the precipitate is separated by centrifugation or filtration; the precipitate needs to be washed before drying, and the drying temperature is 60-80℃. Deionized water at 50-70℃ is used for washing, as deionized water at this temperature has excellent dissolving, washing and removal properties for impurities in the precipitate.

[0021] The above-mentioned technical solution is used to prepare a battery-grade iron phosphate method, which includes the following steps: (1) Prepare iron hydroxide powder and phosphoric acid; (2) Dilute the phosphoric acid with deionized water to form a phosphoric acid solution, and then add the iron hydroxide and phosphoric acid solution to the reactor and stir; (3) After stirring thoroughly, add the catalyst, and add the dispersant and crystal inducing agent within 30 to 40 minutes after the reaction starts, and heat the reaction; (4) After the heating reaction is completed, separate the precipitate, and then wash and dry the separated precipitate. After drying, crush and screen it to obtain the prepared iron phosphate.

[0022] Advantages of this invention:

[0023] 1. The preparation method is simple and easy to implement, and does not require a large amount of equipment or complex processes.

[0024] 2. It can be produced on a large scale and has good economic benefits.

[0025] 3. The products produced have stable and excellent quality, which can meet the needs of the new energy battery field.

[0026] 4. Products can be produced in a relatively short time. Attached Figure Description

[0027] Figure 1 The XRD pattern of the product prepared in Example 2 of this invention;

[0028] Figure 2 The image shows the SEM crystal morphology of the product prepared in Example 2 of this invention.

[0029] Figure 3 This is the XRD analysis diagram of the product prepared in Comparative Example 1 of this invention;

[0030] Figure 4 This is a SEM image of the crystal morphology of the product prepared in Comparative Example 1 of this invention;

[0031] Figure 5 This is the XRD analysis diagram of the product prepared in Comparative Example 3 of the present invention;

[0032] Figure 6 This is a SEM image of the crystal morphology of the product prepared in Comparative Example 3 of this invention.

[0033] Figure 7 This is the XRD analysis diagram of the product prepared in Comparative Example 4 of this invention;

[0034] Figure 8 The image shows the SEM crystal morphology of the product prepared in Comparative Example 4 of this invention. Detailed Implementation

[0035] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0036] Example 1:

[0037] 1. Preparation of raw materials: Prepare 107g of Fe(OH)3 powder and 118g of H3PO4 solution with a concentration of 85%, and dilute with deionized water to 540ml of phosphoric acid solution.

[0038] 2. Reactor preparation: A 1L high-temperature and high-pressure reactor is used as the reactor, and its internal material is made of 314 stainless steel.

[0039] 3. Reaction Process: The prepared Fe(OH)3 powder and H3PO4 solution were added to the reactor and stirred thoroughly. Then, 8.3g of ammonia solution (catalyst) was added, and the reaction was heated. Within 30-40 minutes after the reaction, 0.8g of dispersant and 0.9g of crystallization inducing agent were added. The reaction temperature was maintained at 220℃, and the reaction time was 8 hours. After the reaction was completed, the product was cooled and subjected to solid-liquid separation.

[0040] 4. Product Collection: After the reaction is complete, the precipitate is separated by centrifugation, washed, dried, crushed, screened, and packaged to obtain the prepared ferric phosphate product. The drying temperature is 60℃.

[0041] The crystallization inducing agent is the standard reagent ferric phosphate.

[0042] The dispersant is sodium dodecyl sulfate.

[0043] Example 2:

[0044] 1. Preparation of raw materials: Prepare 107g of Fe(OH)3 powder and 118g of H3PO4 solution with a concentration of 85%, and dilute with deionized water to 540ml of phosphoric acid solution.

[0045] 2. Reactor preparation: A 1L high-pressure steel autoclave was used as the reactor.

[0046] 3. Reaction process: The prepared Fe(OH)3 powder and H3PO4 solution were added to the reactor and stirred thoroughly. Then, 8.3g of ammonia solution (catalyst) was added, and the reaction was heated. Within 30-40 minutes after the reaction, 0.8g of dispersant and 0.9g of crystallization inducing agent were added. The reaction temperature was maintained at 250℃, and the reaction time was 8 hours. After the reaction was completed, the product was cooled and subjected to solid-liquid separation.

[0047] 4. Product Collection: After the reaction is complete, the precipitate is separated by filtration or other methods. The product is washed, dried, crushed, screened, and packaged to obtain the prepared ferric phosphate product. The drying temperature is 70℃.

[0048] The crystallization inducing agent is the standard reagent ferric phosphate.

[0049] The dispersant is sodium dodecyl sulfate.

[0050] Example 3:

[0051] 1. Preparation of raw materials: Prepare 107g of Fe(OH)3 powder and 118g of H3PO4 solution with a concentration of 85%, and dilute with deionized water to 540ml of phosphoric acid solution.

[0052] 2. Reactor preparation: A 1L high-pressure steel autoclave was used as the reactor.

[0053] 3. Reaction process: The prepared Fe(OH)3 powder and H3PO4 solution were added to the reactor and stirred thoroughly. Then, 8.3g of ammonia solution (catalyst) was added, and the reaction was heated. Within 30-40 minutes after the reaction, 0.8g of dispersant and 0.9g of crystallization inducing agent were added. The reaction temperature was maintained at 280℃, and the reaction time was 8 hours. After the reaction was completed, the product was cooled and subjected to solid-liquid separation.

[0054] 4. Product Collection: After the reaction is complete, the precipitate is separated by centrifugation, washed, dried, crushed, screened, and packaged to obtain the prepared iron phosphate product. The drying temperature is 80℃.

[0055] The crystallization inducing agent is the standard reagent ferric phosphate.

[0056] The dispersant is sodium dodecyl sulfate.

[0057] The performance indicators of the samples obtained from the above three sets of examples are as follows:

[0058] The product specifications for iron phosphate and iron phosphate for batteries should conform to the technical specifications of HG / T 4701-2014, as shown in Table 1.

[0059] Table 1. Sample Indicators and Standard Technical Indicators of Ferric Phosphate

[0060]

[0061] Product XRD analysis:

[0062] XRD analysis of the sample from Example 2 revealed that, compared with the standard card COD 9012512 ferric phosphate, this sample exhibited better crystallinity. Figure 1 :

[0063] Product SEM crystal morphology:

[0064] SEM crystal morphology analysis of the product in Example 2 revealed that the material prepared by this process is plate-like, and the primary grains are small, at the nanoscale. Figure 2 .

[0065] Comparative Example 1:

[0066] 1. Preparation of raw materials: Prepare 107g of Fe(OH)3 powder and 118g of H3PO4 solution with a concentration of 85%, and dilute with deionized water to 540ml of phosphoric acid solution.

[0067] 2. Reactor preparation: A 1L high-pressure steel autoclave was used as the reactor.

[0068] 3. Reaction process: Add the prepared Fe(OH)3 powder and H3PO4 solution to the reactor and stir thoroughly. Then add 8.3g of ammonia solution (catalyst) and 0.8g of dispersant. Heat the reactor and maintain the reaction temperature at 250℃ for 8 hours. After the reaction is complete, cool the product and perform solid-liquid separation.

[0069] 4. Product collection: After the reaction is complete, the precipitate is separated by centrifugation or filtration, washed and dried, and then crushed, screened and packaged to obtain the prepared iron phosphate product.

[0070] The difference between this comparative example and Example 2 is that no crystal inducer was introduced. The test results show that the crystal morphology of the product obtained from the reaction is uneven and the crystallinity is poor.

[0071] Samples were subjected to XRD analysis, such as Figure 3 :

[0072] Product SEM crystal morphology as follows Figure 4 .

[0073] Comparative Example 2:

[0074] 1. Preparation of raw materials: Prepare 107g of Fe(OH)3 powder and 118g of H3PO4 solution with a concentration of 85%, and dilute with deionized water to 540ml of phosphoric acid solution.

[0075] 2. Reactor preparation: A 1L high-pressure steel autoclave was used as the reactor.

[0076] 3. Reaction process: The prepared Fe(OH)3 powder and H3PO4 solution were added to the reactor and stirred thoroughly. Then, 8.3 g of ammonia solution (catalyst) and 0.9 g of crystal inducing agent were added. The reactor was heated to maintain the reaction temperature at 250℃ for 8 hours. After the reaction was completed, the product was cooled and subjected to solid-liquid separation.

[0077] 4. Product collection: After the reaction is complete, the precipitate is separated by centrifugation or filtration, washed and dried, and then crushed, screened and packaged to obtain the prepared iron phosphate product.

[0078] The difference between this comparative example and Example 2 is that no dispersant was introduced, and the test results show that the uniformity of the crystal particles of the product obtained from the reaction is poor.

[0079] Comparative Example 3:

[0080] The preparation method of Example 2 was used. The difference between this comparative example and Example 2 is that the crystal inducer was added within 20 to 29 minutes after the heating reaction in step 3.

[0081] Samples were subjected to XRD analysis, such as Figure 5 :

[0082] Product SEM crystal morphology as follows Figure 6 .

[0083] Comparative Example 4:

[0084] The preparation method of Example 2 was used. The difference between this comparative example and Example 2 is that the crystal inducer was added 40 minutes after the heating reaction in step 3.

[0085] Samples were subjected to XRD analysis, such as Figure 7 :

[0086] Product SEM crystal morphology as follows Figure 8 .

[0087] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing battery-grade iron phosphate, characterized in that, Includes the following steps: Step (1) Prepare ferric hydroxide powder and phosphoric acid; Step (2) Dilute phosphoric acid with deionized water to form a phosphoric acid solution, and then add ferric hydroxide and the phosphoric acid solution into the reactor and stir. After stirring thoroughly in step (3), add the catalyst and heat the reaction. 30-40 minutes after the reaction begins, add the dispersant and crystallization inducer. The crystallization inducer is ferric phosphate, and the amount of ferric phosphate added is 1-5‰ of the total reaction solution weight. The catalyst is one or both of sodium hydroxide and ammonia solution, and the amount of the catalyst added is 1-2% of the total reaction solution weight. Adjust the pH to 1.5-2.

5. The amount of dispersant added is 1-2‰ of the total reaction solution weight. The heating conditions are 200-300℃ for 4-12 hours. After the heating reaction in step (4) is completed, the precipitate is separated, and then the separated precipitate is washed and dried. After drying, it is crushed and screened to obtain the prepared nanoscale sheet-like iron phosphate crystals.

2. The method for preparing battery-grade iron phosphate as described in claim 1, characterized in that: In step (1), the mass fractions of ferric hydroxide powder and phosphoric acid are 105-110 parts ferric hydroxide and 115-120 parts phosphoric acid, respectively.

3. The method for preparing battery-grade iron phosphate as described in claim 1 or 2, characterized in that: The concentration of phosphoric acid in step (1) is 85%.

4. The method for preparing battery-grade iron phosphate as described in claim 1, characterized in that: The mass fraction of deionized water added in step (2) is 530 to 545 parts.

5. The method for preparing battery-grade iron phosphate as described in claim 1, characterized in that: After the heating reaction in step (4) is completed, the precipitate is separated by centrifugation or filtration. The precipitate needs to be washed before drying, and the drying temperature is 60-80℃.

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