Manufacturing method for iron phosphate precursor for battery

Abstract

To provide a manufacturing method for an iron phosphate precursor for batteries that improves product quality while reducing raw material usage, time costs, and manufacturing complexity.SOLUTION: The manufacturing method for an iron phosphate precursor for batteries includes Step (a): preparing phosphoric acid and iron powder, wherein the apparent density of the iron powder is 2.3 g / cm3 to 2.6 g / cm3, the iron powder has a primary particle size and a secondary particle size, the primary particle size is larger than the secondary particle size, and the weight of the iron powder having the secondary particle size is 10% to 30% of the total weight of the iron powder, Step (b): reacting the phosphoric acid with the iron powder to form a first product, and Step (c): sintering the first product in an air or oxygen atmosphere to generate an iron phosphate precursor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a manufacturing method, and particularly to a method for manufacturing an iron phosphate precursor for a battery. Prior art

[0002] Due to the continuous global energy shortage, the soaring crude oil prices, and the increasing environmental protection awareness in recent years, how to supply environmentally friendly, clean, and efficient energy has become the biggest challenge for the related industries. Among various alternative energies, the chemical battery technology is a technology that is currently being actively researched and developed in the industrial circle. As the related industries continue to invest in research and development, the battery technology has not only been continuously refined and improved, but also has been widely used in daily life such as household appliances, medical devices, electric bicycles, electric motorcycles, electric vehicles, and electric buses.

[0003] The lithium iron phosphate (LiFePO 4 , also called LFP) composite material battery has no explosion risk and has the advantages of high current and long cycle life. Therefore, it has been widely accepted in the market as a battery to replace low-power and highly polluting batteries such as lead-acid, nickel-metal hydride, and nickel-cadmium batteries. After years of research and development, the nano metal oxide co-crystalline lithium iron phosphate compound (LFP-NCO) battery has been developed. In addition to forming a single compound formed by a precursor containing lithium, iron, phosphorus, and a metal or metal compound, since the material is a high-purity and non-coated material, it can improve the problems of low conductivity and high impurities of the conventional lithium iron phosphate material, and is also cheaper than the conventional lithium iron phosphate material, with excellent market competitiveness and has become the mainstream material in the current market.

[0004] However, the manufacturing method of the nano metal oxide co-crystalline lithium iron phosphate compound is mainly prepared by the reaction of iron phosphate (FePO 4 ), lithium hydroxide (LiOH), and lithium carbonate (Li 2 CO 3 ). Lithium hydroxide (LiOH) and lithium carbonate (Li 2 CO 3) The form of the iron phosphate precursor before reacting affects the production efficiency of the lithium iron phosphate compound. Since the iron phosphate precursor is mainly prepared from iron and phosphoric acid, it is necessary to consider the reaction rate, the influence of heat generation, and the difficulty of manufacturing operations during the reaction process. The conversion rate of the obtained iron phosphate precursor also affects the product quality.

[0005] Therefore, how to provide a manufacturing method of an iron phosphate precursor for a battery is a problem to be solved in order to improve the product quality, reduce the raw materials, time cost, and the difficulty of manufacturing operations, and solve the drawbacks of the prior art.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to provide a manufacturing method of an iron phosphate precursor for a battery that improves the product quality and reduces the raw materials, time cost, and the difficulty of manufacturing operations.

[0007] Another object of the present invention is to provide a manufacturing method of an iron phosphate precursor for a battery. By controlling the specifications of the raw iron powder, optimizing the manufacturing reaction of the iron phosphate precursor, and suppressing the increase in the difficulty of operation in the manufacturing process due to too fast a reaction rate. Also, in the secondary reaction of phosphoric acid, deionized water, and iron powder, when the iron powder reactant is not completely reacted, the amorphous iron phosphate film adhering to the surface of the iron powder reactant is removed by combining the pulverization process, so that the iron powder reactant can contact phosphoric acid again and react sufficiently, effectively reducing the waste of raw materials and comprehensively improving the conversion rate of the iron phosphate precursor.

[0008] Another object of the present invention is to provide a method for manufacturing an iron phosphate precursor for a battery. Through the secondary reaction of phosphoric acid, deionized water, and iron powder, the reaction between phosphoric acid and iron powder can be completed, effectively reducing waste of raw materials and comprehensively improving the quality of the product. By combining the method for manufacturing the iron phosphate precursor to form a battery composite material, the time required for grinding can be significantly shortened, thereby reducing the unit time and cost. At the same time, the pH value sensitivity during the manufacturing process can be reduced, avoiding sticking and clogging of pipelines, stabilizing the temperature during the control process, and reducing the operational difficulty of the manufacturing process and production line.

Means for Solving the Problems

[0009] To achieve the above object, in a broad embodiment of the present invention, there is provided a method for manufacturing an iron phosphate precursor for a battery, comprising step (a) of preparing phosphoric acid and iron powder, wherein the apparent density of the iron powder is 2.3 g / cm 3 ~2.6 g / cm 3 and the iron powder has a first particle size and a second particle size, the first particle size is larger than the second particle size, and the weight of the iron powder having the second particle size is 10% - 30% of the total weight of the iron powder; step (b) of reacting the phosphoric acid and the iron powder to produce a first product; and step (c) of sintering the first product in an air or oxygen atmosphere to produce an iron phosphate precursor. In an embodiment, the BET surface area of the iron powder is 700 cm 2 / g - 1300 cm 2 / g, the first particle size is larger than 45 μm and less than 212 μm, and the second particle size is 45 μm or less. In an embodiment, step (c) is continuously sintered for at least 1 hour within a temperature range of 610°C to 670°C. In an embodiment, the first particle size is larger than 45 μm and less than 212 μm, the second particle size is 45 μm or less, and the weight of the iron powder having the second particle size is 10% - 25% of the total weight of the iron powder. In one embodiment, the first product is amorphous iron phosphate, with the chemical formula a-FePO 4 ·xH 2 O, and x > 0. In one embodiment, step (b) includes step (b11) of dissolving a first quantity of phosphoric acid in deionized water to produce a first phosphoric acid solution in a first temperature environment, step (b12) of reacting the first phosphoric acid solution with iron powder in a second temperature environment, cooling the temperature to a third temperature after reaching the second temperature, and maintaining it for a first period of time, and step (b13) of cooling the temperature to a fourth temperature, adding a second phosphoric acid solution containing a second quantity of phosphoric acid, and reacting the first phosphoric acid solution, the second phosphoric acid solution, and the iron powder for a second period of time to produce a first product. In one embodiment, the weight ratio of the first quantity to the second quantity is 3:1. In one embodiment, the first temperature is 35°C to 45°C, the second temperature is 60°C or less, the third temperature is 50°C or less, and the fourth temperature is 30°C or less. In one embodiment, the first period of time is at least 3 hours, and the second period of time is 5 hours to 9 hours. In one embodiment, step (b) includes step (b21) of performing a first grinding so that the D99 particle size of the particles of the first product is smaller than a first length, and step (b22) of continuously reacting for a third period of time. In one embodiment, the first length is less than 100 μm, and the third period of time is 6 hours to 12 hours. In one embodiment, step (b) includes step (b31) of adding a carbon source and a metal compound, and the carbon source, the metal compound, and the first product form a precursor solution and perform a second grinding, and step (b32) of performing a spray drying operation on the precursor solution when the D70 particle size of the particles in the precursor solution is smaller than a second length in the second grinding. In one embodiment, the spray drying operation is realized by a rotary disk spray dryer. The inlet temperature of the rotary disk spray dryer is 210°C, the outlet temperature is 95°C, and the rotation speed of the rotary disk is 300 Hz to 400 Hz. In one embodiment, the second length is 1 μm to 10 μm. In one embodiment, the rotational speeds of the first pulverization and the second pulverization are 450 rpm to 650 rpm. In one embodiment, the metal compound and the iron phosphate precursor form an iron phosphate precursor composite material in step (c), and then are sintered to form a battery composite material, and the chemical formula of the battery composite material is LiFePO 4 and the metal compound is a lithium-containing compound In one embodiment, the lithium-containing compound is selected from lithium hydroxide, lithium carbonate, and mixtures thereof, and the battery composite material is a nanometal oxide co-crystalline lithium iron phosphate compound (LFP-NCO). In one embodiment, step (c) includes maintaining at 325 °C for 0.5 hour, maintaining at 550 °C for 0.5 hour, and maintaining at 650 °C for 1 hour.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

[0011] Some exemplary embodiments embodying the features and advantages of the present invention will be described in detail below. The present invention can be variously modified without departing from its scope. The following description and drawings are used to explain the present invention and are not intended to limit it. In the detailed description of the present invention, the statement that a first feature is disposed above or over a second feature includes embodiments where the first and second features are directly connected and embodiments where the first and second features are not directly connected but are connected via other structures therebetween. Also, different embodiments in this specification use repeated reference numerals and / or markings. These repeated reference numerals and markings are for simplicity and clarity and are not intended to limit the relationship between each embodiment and / or external structure. Although the numerical ranges and parameters in this specification are approximations, the values are described as accurately as possible in specific examples. Also, terms such as "first," "second," "third," etc. are used to describe different components described in the claims, and these components are not limited to these terms. In the context of embodiments, although the corresponding components are denoted by different reference signs, the first component may be denoted as the second component, and the second component may be denoted as the first component without departing from the embodiments of the present invention. Also, the term "and / or" means one and more related elements or all combinations thereof. Unless clearly defined in the embodiments regarding operations / actions, all numerical ranges, amounts, numbers, percentages, etc. (e.g., angles, durations, temperatures, operating conditions, ratios, and corresponding percentages, etc.) described in this specification should be understood as being "about" or "substantially" in all embodiments. Also, unless otherwise stated in the content, the numerical values of the present invention and the claims can be taken as approximate values that can change as needed. For example, each parameter may be interpreted by applying the normal rounding principle in light of at least the significant digits described. Also, the numerical ranges in this specification can be expressed as from one endpoint to the other endpoint or as the range between the two endpoints.Note that all ranges described in this specification include the endpoints unless otherwise defined.

[0012] Figure 1 is a flowchart of a method for manufacturing an iron phosphate precursor for a battery in a preferred embodiment of the present invention. As shown in Figure 1, the steps of the method for manufacturing the battery composite material of the present invention are as follows. First, as shown in step S100, phosphoric acid and iron powder are prepared. Here, the chemical formula of phosphoric acid is H 3 PO 4 and the chemical formula of iron powder is Fe. Specific specifications of iron powder are used to optimize the production reaction of the iron phosphate precursor and prevent the reaction rate from being too fast, which may increase the difficulty of process operation or cause safety problems. In this embodiment, the range of the apparent density of the iron powder is 2.3 g / cm 3 ~2.6 g / cm 3 . The particle size of the iron powder includes a first particle size and a second particle size. For example, by a screening method, it is divided into two ranges. In this embodiment, the first particle size is a coarse powder less than 212 μm and larger than 45 μm, and the second particle size is a fine powder of 45 μm or less, that is, the first particle size is larger than the second particle size (the first particle size is larger than the second particle size). The weight of the iron powder with the first particle size accounts for 90% - 70% of the total weight of the iron powder, and the weight of the iron powder with the second particle size accounts for 10% - 30% of the total weight of the iron powder. In other words, by the screening method, the maximum particle size of the iron powder is less than 212 μm, and iron powder ≤ 45 μm (that is, iron powder with a particle size of 45 μm or less) can obtain iron powder that meets the predetermined requirement that the weight of the fine powder is 10% - 30% of the total weight of the iron powder. Preferably, the weight of the iron powder with the first particle size is 90% - 75% of the total weight of the iron powder, and the weight of the iron powder with the second particle size is 10% - 25% of the total weight of the iron powder, that is, the weight of the iron powder ≤ 45 μm is 10% - 25% of the total weight of the iron powder. In this embodiment, the BET surface area of the iron powder is 700 cm 2 / g ~ 1300 cm 2It is / g. Note that the first particle size and the second particle size can be selected according to actual needs. For example, sieving can be divided into two ranges: coarse powder and fine powder. Hereinafter, the first particle size and the second particle size will be described by taking, as an example, the coarse powder with a particle size less than 212 μm and greater than 45 μm obtained by sieving and the fine powder with a particle size of ≦ 45 μm (that is, 45 μm or less), but the present invention is not limited thereto.

[0013] As shown in step S200, phosphoric acid and iron powder are reacted to form a first product. In this embodiment, the first product is amorphous iron phosphate, and its chemical formula is a-FePO 4 ·xH 2 O (x > 0).

[0014] As shown in step S300, in an air or oxygen atmosphere, the first product is sintered to produce an iron phosphate precursor. In this embodiment, when the first product is continuously sintered at a temperature in the range of 610 °C to 670 °C for at least 1 hour, an iron phosphate precursor can be obtained. Note that the present invention is not limited thereto.

[0015] Please refer to FIGS. 1 and 2. FIG. 2 is a detailed flowchart of the method for manufacturing the iron phosphate precursor for a battery according to the present invention. As shown in FIGS. 1 and 2, the detailed process of step S200 of the method for manufacturing the iron phosphate precursor for a battery according to the present invention includes the following steps. As shown in step S201, in a first temperature environment (for example, an environment preheated to 35°C to 45°C), a first quantity of phosphoric acid is dissolved in deionized water to form a first phosphoric acid solution. It is preferably preheated to 42°C, but the present invention is not limited thereto. Then, as shown in step S202, in a second temperature environment, the first phosphoric acid solution and iron powder are reacted. After reaching the second temperature, the temperature is decreased to a third temperature and maintained for a first period of time. According to the technical idea of the present invention, after mixing, it is also possible to titrate the iron powder aqueous solution with other compounds that release phosphate ions into the aqueous solution, but the present invention is not limited thereto. The second temperature is 60°C or less, preferably 60°C. The third temperature is 50°C or less, preferably 50°C. The first period of time is at least 3 hours, preferably 3 hours.

[0016] In an embodiment, the preferred step S202 is to react the first phosphoric acid solution and iron powder in an environment of 60°C. After reaching 60°C, the temperature is decreased to 50°C and maintained at the same temperature for 3 hours. However, the present invention is not limited thereto. Then, as shown in step S203, the temperature is decreased to a fourth temperature, and a second phosphoric acid solution having a second quantity of phosphoric acid is added. The first phosphoric acid solution, the second phosphoric acid solution, and the iron powder continuously react for a second period of time to form a first product.

[0017] In this embodiment, the first product is an amorphous form of iron phosphate with a chemical formula of a-FePO 4 ·xH 2 O (x>0). The fourth temperature is 30°C or less, preferably 30°C. The second period of time is 5 hours to 9 hours. The weight ratio of the first quantity to the second quantity is 3:1, that is, the first quantity is 75% and the second quantity is 25%.

[0018] Please refer to FIG. 3 in combination with FIG. 1. FIG. 3 is another detailed flowchart of the method for manufacturing the iron phosphate precursor for a battery according to the present invention. As shown in FIGS. 1 and 3, the details of step S200 of the method for manufacturing the iron phosphate precursor for a battery according to the present invention include the following steps. As shown in step S211, after the reaction is completed in 5 to 9 hours, first grinding is performed so that the D99 particle size of the particles of the first product is smaller than the first length. Then, as shown in step S212, in order to promote the reaction and further complete the reaction between phosphoric acid and iron powder, the reaction is continued for 3 hours. In this embodiment, the iron powder has a specific specification (being iron powder with a specific specification), and the powder metal has the characteristic of a fast reaction rate. However, if the reaction rate is too fast, a shielding layer (barrier) is likely to be formed on the surface of the powder. In this embodiment, when the iron powder has not completely reacted with phosphoric acid, by appropriate grinding, the amorphous iron phosphate film adhering to the surface of the iron powder can be removed, whereby the iron powder reactant can be brought into contact with phosphoric acid, so that the entire reaction can proceed more completely.

[0019] In this embodiment, the first length is less than 100 μm, and the range of the 3 hours is 6 to 12 hours. In this embodiment, the first grinding is performed, for example, by performing a grinding operation at a first rotation speed, and the first rotation speed is 450 to 650 revolutions per minute (450 rpm to 650 rpm), preferably 550 revolutions per minute (550 rpm). Through the secondary reaction of phosphoric acid, deionized water and iron powder, the phosphoric acid solution and iron powder can react sufficiently, effectively reducing the waste of raw materials and achieving the effect of comprehensively improving the quality of the product.

[0020] Incidentally, the preparation of the iron phosphate precursor for the battery of the present invention can be combined with the preparation of the battery composite material. FIG. 4 is a detailed flowchart of a method for manufacturing a battery composite material combined with the iron phosphate precursor for the battery of the present invention. FIG. 5 is another detailed flowchart of a method for manufacturing a battery composite material combined with the iron phosphate precursor for the battery of the present invention. In the present embodiment, as shown in step S221, a carbon source (carbon material) and a metal compound required for the battery composite material are added to the first product formed after the phosphoric acid solution and iron powder have sufficiently reacted, and the carbon source, the metal compound, and the first product form a precursor solution, and a second grinding is performed. In the present embodiment, the carbon source is a saccharide, an organic compound, a polymer or a polymeric material. In some embodiments, the saccharide includes fructose, sucrose, lactose, galactose, etc., but the present invention is not limited thereto. Further, the polymeric material is polyvinylpyrrolidone (PVP, chemical formula (C 6 H 9 NO) n ), but the present invention is not limited thereto. In the present embodiment, the metal compound is lithium carbonate (chemical formula Li 2 CO 3 ), lithium hydroxide (chemical formula LiOH), or another compound containing lithium atoms, or a mixture of a plurality of compounds containing lithium atoms, but the present invention is not limited thereto.

[0021] Next, as shown in step S222, the particles in the precursor solution are pulverized by the second pulverization. When the D70 particle size becomes less than the second length, a spray drying operation is performed on the precursor solution. In this embodiment, the rotation speed range of the second pulverization may be the same as the rotation speed range of the first pulverization, and is 450 to 650 rotations per minute. The second length range is 1 μm to 10 μm. In this embodiment, the spray drying operation is performed using a rotary disk spray dryer. The inlet temperature of the rotary disk spray dryer is 210°C, the outlet temperature is 95°C, and the rotation speed of the rotary disk is 300 Hz to 400 Hz, but the present invention is not limited thereto. In this embodiment, the carbon source is mainly added to prevent the growth of particles and avoid excessive melting. The dispersant used in the well-known spray drying operation is a dispersant for metal ions. In the present invention, a carbon source is used instead of the well-known dispersant. Since the carbon source is an organic compound, it not only functions as an auxiliary dispersant, but can also be removed by firing in air or oxygen thereafter, so that no other metal ions remain and the purity of the product can be further improved. Note that the present invention is not limited thereto.

[0022] In step S301, the metal compound after spray drying and the iron phosphate precursor are sintered at a high temperature. In this embodiment, the metal compound after spray drying and the iron phosphate precursor are placed in an air or oxygen atmosphere and maintained at 325°C for 0.5 hours, 550°C for 0.5 hours, and 650°C for 1 hour. Finally, as shown in step S302, the iron phosphate precursor composite material formed by the metal compound and the iron phosphate precursor is sintered to form a battery composite material (for example, LiFePO 4 ).) In other embodiments, in step S221, for example, metal oxides such as V 2 O 5 , MgO are added to obtain a LiFePO 4 material containing the metal oxide. The LiFePO 4 material of the metal oxide can be called "nano metal oxide co-crystalline lithium iron phosphate compound (LFP-NCO)".

[0023] According to the above content, in the secondary reaction of phosphoric acid, deionized water and iron powder, the present invention can fully react phosphoric acid and iron powder, effectively reduce waste, and comprehensively improve the quality of products. By combining the method for manufacturing the iron phosphate precursor to form a battery composite material, the time required for grinding can be significantly shortened, and the unit time and cost can be reduced. At the same time, by combining the change of the plurality of parameters, the pH value sensitivity of the manufacturing process can be reduced, adhesion and retention of raw materials and clogging of pipelines can be avoided, the temperature of the control process can be stabilized, and the operation difficulty of the manufacturing process and production line can be reduced.

[0024] The following describes the method for manufacturing the iron phosphate precursor for a battery according to the present invention with reference to exemplary embodiments.

[0025] Example 1

[0026] First, prepare 12.385 g of phosphoric acid (purity 85% or more), 50 cc of deionized water, and 6 g of iron powder (purity 99% or more). The apparent density range of the iron powder is 2.3 g / cm 3 ~2.6 g / cm 3 . The maximum particle size of the iron powder is less than 212 μm, and the weight of the fine powder with iron powder ≤ 45 μm accounts for 21.6% of the total weight of the iron powder. The phosphoric acid and iron powder are put into a water jacket reaction tank in the above-mentioned steps S201 and S202 for secondary reaction and stirring. After the second phosphoric acid solution of the second quantitative phosphoric acid is added and the reaction continues for 5 hours, as shown in the above-mentioned steps S211 and S212, grinding is performed using a horizontal grinding sand mill (rotation speed 550 rpm), and the first grinding is performed so that the D99 particle size of the particles of the first product is less than 100 μm, and the reaction is carried out for 6 hours at the third hour. When the first product after spray drying is continuously sintered at a temperature range of 610 °C to 670 °C for at least 1 hour, an iron phosphate precursor can be obtained. The X-ray Diffraction (XRD) analysis results are shown in FIG. 6. As a result of comparison with the standard diffraction pattern (JCPDS Card), its structure was confirmed to be FePO 4 .

[0027] Example 2

[0028] In Example 2, 12.385 g of phosphoric acid (purity 85% or higher), 50 cc of deionized water, and 6 g of iron powder (purity 99% or higher) are prepared. The range of the apparent density of the iron powder used for manufacturing the iron phosphate precursor for batteries is 2.3 g / cm 3 ~2.6 g / cm 3 . The maximum particle size of the iron powder is less than 212 μm, and the weight of the fine powder with iron powder ≤ 45 μm is 13.3% of the total weight of the iron powder. The phosphoric acid and the iron powder are put into a water jacket reaction tank in the aforementioned steps S201 and S202 to perform a secondary reaction and stirring. The initial reaction rate between the phosphoric acid and the iron powder is appropriately medium (the initial temperature rising rate is 1.54 °C / min), the operability during the reaction process is excellent, and peptization is performed using phosphoric acid. The relative conversion rate of the obtained first product is about 90.3%, the final particle size D99 is 110.2 μm, and the final pH value is 2.41.

[0029] Example 3

[0030] In Example 3, 12.385 g of phosphoric acid (purity 85% or higher), 50 cc of deionized water, and 6 g of iron powder (purity 99% or higher) are prepared. The range of the apparent density of the iron powder used for manufacturing the iron phosphate precursor for batteries is 2.3 g / cm 3 ~2.6 g / cm 3 . The maximum particle size of the iron powder is less than 212 μm, and the weight of the fine powder with iron powder ≤ 45 μm accounts for 25.0% of the total weight of the iron powder. The phosphoric acid and the iron powder are put into a water jacket reaction tank in the aforementioned steps S201 and S202 to perform a secondary reaction and stirring. The initial reaction rate between the phosphoric acid and the iron powder is appropriately medium (the initial temperature rising rate is 1.54 °C / min), and manual assistance is required to perform peptization during the reaction process. The relative conversion rate of the obtained first product is about 98.1%, the final particle size D99 is 133.4 μm, and the final pH value is 2.35.

[0031] Example 4

[0032] In Example 4, 12.385 g of phosphoric acid (purity 85% or more), 50 cc of deionized water, and 6 g of iron powder (purity 99% or more) are prepared. The range of the apparent density of the iron powder used for manufacturing the iron phosphate precursor for batteries is 2.3 g / cm 3 ~2.6 g / cm 3 . The maximum particle size of the iron powder is less than 212 μm, and the weight of the fine powder with iron powder ≤ 45 μm is 16.4% of the total weight of the iron powder. In the aforementioned steps S201 and S202, phosphoric acid and iron powder are put into a water jacket reaction tank for secondary reaction and stirring. The initial reaction rate between phosphoric acid and iron powder is gentle (initial temperature rise rate 1.40 °C / min), and manual assistance is required for peptization during the reaction process. The relative conversion rate of the obtained first product is about 95.9%, the final particle size D99 is 119.4 μm, and the final pH value is 2.23.

[0033] Comparative Example 1

[0034] In Comparative Example 1, 12.385 g of phosphoric acid (purity 85% or more), 50 cc of deionized water, and 6 g of iron powder (purity 99% or more) are prepared. The range of the apparent density of the iron powder is 2.3 g / cm 3 ~2.6 g / cm 3 . The maximum particle size of the iron powder is less than 212 μm, and the weight of the fine powder with iron powder ≤ 45 μm accounts for 5.0% of the total weight of the iron powder. In the aforementioned steps S201 and S202, phosphoric acid and iron powder are put into a water jacket reaction tank for secondary reaction and stirring. The initial reaction rate between phosphoric acid and iron powder is fast (initial temperature rise rate 1.71 °C / min), the operability during the reaction process is excellent, and there is no need to perform peptization using phosphoric acid. The relative conversion rate of the obtained first product is about 85.1%, the final particle size D99 is 100.0 μm, and the final pH value is 2.51.

[0035] Table 1 shows the comparison of the reaction processes and final results of Comparative Example 1, Example 2, Example 3, and Example 4. JPEG2025083271000002.jpg57142

[0036] FIG. 7 is a diagram showing the relationship between the ratio of fine powder of raw iron powder ≤ 45 μm and the relative conversion rate of the obtained first product. FIG. 8 is a diagram showing the relationship between the ratio of fine powder of raw iron powder ≤ 45 μm and the final particle size D99 of the obtained first product. From the results shown in Table 1 and FIGS. 7 to 8, as the ratio of fine powder of iron powder ≤ 45 μm increases, the relative conversion rate of the first product also increases, and the final particle size D99 is also relatively large. When the ratio of fine powder of iron powder ≤ 45 μm approaches 30%, the increase in the relative conversion rate tends to level off. The ratio of fine powder of iron powder ≤ 45 μm has no relation with the final pH value. By increasing the ratio of fine powder of iron powder ≤ 45 μm, the relative conversion rate and the final particle size of the first product can be effectively increased, but in the reaction process, the gelation expansion is intense, and it is necessary to increase the usage amount of phosphoric acid for peptization. Also, human assistance is required for peptization, and the operability is not good. Therefore, the present invention controls the specifications of the raw iron powder, and provides those with an apparent density range of 2.3 g / cm 3 ~2.6 g / cm 3 , a BET surface area range of 700 cm 2 / g to 1300 cm 2 / g, a maximum particle size of less than 212 μm, and the weight of fine powder of iron powder ≤ 45 μm accounting for 10% to 30% of the total weight of the iron powder, optimizing the reaction for producing the iron phosphate precursor, avoiding the increase in the difficulty of operation in the manufacturing process due to the reaction rate being too fast, and at the same time, being able to improve the quality of the product.

[0037] In this embodiment, the gelation reaction during the above-described reaction process can be regarded as the initial reaction degree (heat release degree). The gelation reaction can be suppressed by increasing the holding temperature of the water jacket reaction tank or increasing the ratio of iron powder with a certain particle size. The holding temperature of the water jacket reaction tank is controlled at 45°C to 60°C and does not affect the conversion rate of the first product in the subsequent process. However, when the holding temperature of the water jacket reaction tank rises to 65°C, the conversion rate of the first product decreases.

[0038] In other embodiments, in the secondary reaction of phosphoric acid, deionized water, and iron powder, if the iron powder reactant has not completely reacted, the grinding process is further combined to remove the amorphous iron phosphate film adhering to the surface of the iron powder reactant, and the iron powder reactant is brought into contact with phosphoric acid again to react sufficiently. Thereby, waste of raw materials can be effectively reduced, and the conversion rate of the iron phosphate precursor can be improved as a whole. The method for manufacturing the iron phosphate precursor can be combined with the manufacturing of the battery composite material, significantly shortening the time required for grinding, and accordingly, the unit time and cost can also be reduced. At the same time, by combining the changes in the plurality of parameters, the pH value sensitivity of the manufacturing process can be reduced, adhesion and retention of raw materials and clogging of pipelines can be avoided, the temperature of the control process can be stabilized, and the operation difficulty of the manufacturing process and the production line can be reduced. It should be noted that the application of the iron phosphate precursor of the present invention is not limited thereto, and the details are omitted.

[0039] As described above, the present invention provides a method for manufacturing an iron phosphate precursor for a battery, which can improve product quality, reduce raw materials, time costs, and the difficulty of manufacturing operations. By controlling the specifications of the raw material iron powder, an optimized manufacturing reaction of the iron phosphate precursor is realized, and it is avoided that the reaction rate is too fast and the operation of the manufacturing process becomes difficult. Further, in the secondary reaction of phosphoric acid, deionized water, and iron powder, if the iron powder reactant has not completely reacted, the grinding process is combined to remove the amorphous iron phosphate film adhering to the surface of the iron powder reactant, and the iron powder reactant can come into contact with phosphoric acid again and react sufficiently, effectively reducing waste of raw materials and improving the conversion rate of the iron phosphate precursor as a whole. Further, in the secondary reaction of phosphoric acid, deionized water, and iron powder, phosphoric acid and iron powder are made to react sufficiently, effectively reducing waste of raw materials and comprehensively improving the quality of the product. By combining the method for manufacturing the iron phosphate precursor to form a battery composite material, the time required for grinding can be significantly shortened, and the unit time and cost can be reduced. At the same time, the pH value sensitivity of the manufacturing process can be reduced, adhesion and retention and pipeline clogging can be avoided, the temperature of the control process can be stabilized, and the operation difficulty of the manufacturing process and the production line can be reduced.

[0040] The present invention has been described in detail by the above-described embodiments and can be changed, improved, and modified in various ways according to the desires of those skilled in the art. Any such changes, improvements, and modifications are all included in the scope of the claims of the present invention.

Description of Reference Numerals

[0041] S100, S200, S201, S202, S203, S211, S212, S221, S222, S300, S301, S302: Steps

Claims

1. A method for producing an iron phosphate precursor for a battery, comprising the steps of: (a) providing phosphoric acid and iron powder, the iron powder having an apparent density of 2.3 g / cm ３ ~2.6g / cm ３ step (a), wherein the particle size of the iron powder has a first particle size and a second particle size, the first particle size is larger than the second particle size, and a weight of the iron powder having the second particle size is 10% to 30% of a total weight of the iron powder; (b) reacting the phosphoric acid with the iron powder to form a first product; and (c) sintering the first product in an air or oxygen atmosphere to produce an iron phosphate precursor.

2. The BET surface area of ​​the iron powder is 700 cm ２ / g to 1300 cm ２ 2. The method for producing an iron phosphate precursor for batteries according to claim 1, wherein the first particle size is greater than 45 μm and less than 212 μm, and the second particle size is 45 μm or less.

3. 2. The method for producing an iron phosphate precursor for batteries according to claim 1, wherein the step (c) comprises continuously sintering at a temperature in the range of 610° C. to 670° C. for at least 1 hour.

4. 2. The method for producing an iron phosphate precursor for batteries according to claim 1, wherein the first particle size is greater than 45 μm and less than 212 μm, the second particle size is 45 μm or less, and a weight of the iron powder having the second particle size is 10% to 25% of a total weight of the iron powder.

5. The first product is an amorphous iron phosphate having the chemical formula a-FePO ４ ・xH ２ 2. The method for producing an iron phosphate precursor for batteries according to claim 1, wherein x is O and x>0.

6. The step (b) (b11) dissolving a first amount of the phosphoric acid in deionized water at a first temperature environment to form a first phosphoric acid solution; Step (b12) of reacting the first phosphoric acid solution with the iron powder in a second temperature environment, and after the second temperature is reached, lowering the temperature to a third temperature and maintaining the temperature for a first time; and (b13) decreasing the temperature to a fourth temperature, adding a second phosphoric acid solution containing a second amount of the phosphoric acid, and reacting the first phosphoric acid solution, the second phosphoric acid solution, and the iron powder for a second time to produce the first product.

7. 7. The method for producing an iron phosphate precursor for batteries according to claim 6, wherein a weight ratio of the first amount to the second amount is 3:

1.

8. 7. The method for producing an iron phosphate precursor for batteries according to claim 6, wherein the first temperature is 35° C. to 45° C., the second temperature is 60° C. or less, the third temperature is 50° C. or less, and the fourth temperature is 30° C. or less.

9. 7. The method for producing an iron phosphate precursor for batteries according to claim 6, wherein the first time is at least 3 hours, and the second time is 5 to 9 hours.

10. The step (b) (b21) performing a first grinding such that the D99 particle size of the particles of the first product is smaller than a first length; and (b22) continuously reacting for a third time.

11. 11. The method for producing an iron phosphate precursor for batteries according to claim 10, wherein the first length is less than 100 μm, and the third time is 6 to 12 hours.

12. The step (b) Step (b31) of adding a carbon source and a metal compound, the carbon source, the metal compound and the first product forming a precursor solution and performing a second grinding; 11. The method for producing an iron phosphate precursor for batteries according to claim 10, further comprising the step (b32) of spray-drying the precursor solution when the D70 particle size of the particles in the precursor solution becomes smaller than a second length in the second grinding.

13. 13. The method for producing an iron phosphate precursor for batteries according to claim 12, wherein the spray drying operation is achieved by a rotary disk spray dryer, the inlet temperature of the rotary disk spray dryer is 210° C., the outlet temperature is 95° C., and the rotation speed of the rotary disk is 300 Hz to 400 Hz.

14. The method for producing an iron phosphate precursor for batteries according to claim 12, wherein the second length is 1 μm to 10 μm.

15. 13. The method for producing an iron phosphate precursor for batteries according to claim 12, wherein a rotation speed of the first pulverization and the second pulverization is 450 rpm to 650 rpm.

16. The metal compound and the iron phosphate precursor are used in step (c) to form an iron phosphate precursor composite, which is then sintered to form a battery composite, the chemical formula of which is LiFePO ４ and the metal compound is a lithium-containing compound.

17. 17. The method for preparing an iron phosphate precursor for a battery according to claim 16, wherein the lithium-containing compound is selected from lithium hydroxide, lithium carbonate and a mixture thereof, and the battery composite material is a nano-metal oxide co-crystal lithium iron phosphate compound (LFP-NCO).

18. 17. The method of claim 16, wherein the step (c) comprises maintaining at 325°C for 0.5 hours, maintaining at 550°C for 0.5 hours, and maintaining at 650°C for 1 hour.

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