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 iron powder, wherein the apparent density of the iron powder ranges from 2.3 g / cm3 to 2.6 g / cm3, the particle size of the iron powder includes 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 with the secondary particle size accounts for 10% to 30% of the total weight of the iron powder, Step (b): preparing phosphoric acid and reacting it with the iron powder to form a first product, and Step (c): sintering the first product in an air or oxygen atmosphere to form an iron phosphate precursor.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a manufacturing method, and more 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 in the related industries. Among various alternative energies, 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, battery technology has been continuously refined, not only improved, but also 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, the material is a high-purity and non-coated material, so 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 may also affect the product quality.

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

Summary of the Invention

Problems to be Solved by the Invention

[0006] The object of the present invention is to provide a manufacturing method for the iron phosphate precursor for batteries, which can improve the product quality, reduce raw materials, time costs, and the difficulty of manufacturing operations.

[0007] Another object of the present invention is to provide a manufacturing method for the iron phosphate precursor for batteries. Control the specifications of the raw iron powder, optimize the manufacturing reaction of the iron phosphate precursor, and suppress 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, phosphoric acid is added to the aqueous iron powder solution formed by mixing iron powder and water in a titration method, and avoid the situation that the reaction rate between phosphoric acid and iron powder is too fast, resulting in too fast a temperature rise of the aqueous solution and affecting the quality of the iron phosphate precursor product. Also, when the iron powder reactant is not completely reacted, by combining the grinding manufacturing process, the amorphous iron phosphate film adhering to the surface of the iron powder reactant can be removed, the iron powder reactant can contact phosphoric acid again and react completely, 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. The secondary reaction of phosphoric acid, deionized water, and iron powder adopts a titration method, with a milder (slower) reaction rate, reacting phosphoric acid with iron powder in a controlled manner, effectively reducing waste of raw materials, comprehensively improving the quality of the product, and during the reaction process of phosphoric acid and iron powder, a large amount of hydrogen is not generated at once, and the safety is excellent. Also, by using the titration method, a violent hydration reaction during the reaction process can be avoided, and the poor operability due to sticking and retention of raw materials can be avoided. 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, sticking 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.

Means for Solving the Problems

[0009] To achieve the above object, in a broad embodiment of the present invention, a method for manufacturing an iron phosphate precursor for a battery is provided, including step (a) of preparing 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 (a); step (b) of preparing phosphoric acid and reacting the phosphoric acid with 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, in step (c), sintering is continuously performed for at least 1 hour within a temperature range of 610°C to 670°C. In one embodiment, the first particle size is greater 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% to 25% of the total weight of the iron powder. In one embodiment, the first product is amorphous iron phosphate, and the chemical formula is a-FePO 4 ·xH 2 O, and x > 0. In one embodiment, step (b) includes step (b11) of mixing deionized water and the iron powder in a first temperature environment to form an iron powder aqueous solution, and step (b12) of adding a first quantity of the phosphoric acid to the iron powder aqueous solution at a constant titration rate in a second temperature environment for reaction, and after reaching the second temperature, cooling to a third temperature and maintaining for a first time, and step (b13) of cooling to a fourth temperature, adding a second quantity of the phosphoric acid, and continuously reacting the phosphoric acid and the iron powder aqueous solution for a second time to form a first product. In one embodiment, the weight ratio of the first quantity to the second quantity is greater than 2.5. 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 35°C or less. In one embodiment, the concentration of the phosphoric acid is 85 wt.%, and the range of the titration rate is 10 mL / min to 40 mL / min. In one embodiment, the first time is at least 3 hours, and the second time is 5 hours to 9 hours. In one embodiment, step (b) includes step (b21) of performing a first grinding, where 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 time. In one embodiment, the first length is less than 100 μm, and the range of the third time is 6 hours to 12 hours. In one embodiment, step (b) includes step (b31) of adding a carbon source and a metal compound, where the carbon source, the metal compound, and the first product form a precursor solution and perform a second grinding, and in the second grinding, when the D70 particle size of the particles in the precursor solution becomes smaller than the second length, performing a spray drying operation on the precursor solution, step (b32). 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 rotation speeds of the first grinding and the second grinding are 450 rotations per minute to 650 rotations per minute. 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. 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 nano metal oxide co-crystalline lithium iron phosphate compound (LFP-NCO). In one embodiment, step (c) includes steps of maintaining at 325°C for 0.5 hours, maintaining at 550°C for 0.5 hours, and maintaining at 650°C for 1 hour.

Brief Description of Drawings

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Figure 1

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Embodiments for Carrying Out the Invention

[0011] Several exemplary embodiments embodying the features and advantages of the present invention are described in detail below. The present invention can be variously modified without departing from its scope, and the following description and drawings are used to explain the present invention and are not intended to limit it. Also, in the detailed description of the present invention, the statement that a first feature is disposed on or above a second feature includes embodiments in which the disposed first feature and the second feature are directly connected, and embodiments in which the first feature and the second feature are not directly connected via another structure between the first feature and the second feature. Also, different embodiments in this specification use duplicate reference numerals and / or markings. These duplicate reference numerals and markings are for the purpose of simplification 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 approximate, their values are described as accurately as possible in specific examples. Also, terms such as "first," "second," "third," etc. are used to describe different configurations described in the claims, and these configurations are not limited to these terms. In the context of embodiments, although the corresponding configurations are denoted by different reference signs, the first configuration may be denoted as the second configuration, and the second configuration may also be denoted as the first configuration without departing from the embodiments of the present invention. Also, the term "and / or" means one and a plurality of related elements or all combinations thereof. Unless clearly defined in the embodiments regarding operations / acts, all numerical ranges, amounts, numbers, percentages, etc. (e.g., angles, holding times, temperatures, operating conditions, ratios, and corresponding percentages, etc.) described in this specification should be understood as the term "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 necessary. 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 ranging from one endpoint to the other endpoint or as the range between the two endpoints.Note that all ranges described in this specification include 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, iron powder is provided. The chemical formula of the 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 iron powder has a first particle size and a second particle size, and is divided into two particle size ranges by, for example, a screening method. In this embodiment, it includes coarse powder with a first particle size of less than 212 μm and greater than 45 μm, and fine powder with a second particle size of 45 μm or less. Here, 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 is 10% - 30% of the total weight of the iron powder. In other words, by the screening method, an iron powder with a maximum particle size of less than 212 μm and the weight of the fine powder of iron powder ≤ 45 μm (that is, iron powder with a particle size of 45 μm or less) satisfying the predetermined requirement of 10% - 30% of the total weight of the iron powder can be obtained. 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 fine powder of 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 the coarse powder with a particle size less than 212 μm and greater than 45 μm and the fine powder with a particle size of ≦ 45 μm (that is, 45 μm or less) obtained by sieving as examples, but the present invention is not limited thereto.

[0013] In step S200, phosphoric acid is provided (prepared), and phosphoric acid and iron powder are reacted to form a first product. Here, the chemical formula of phosphoric acid is H 3 PO 4 This is the case. In this embodiment, the first product is amorphous iron phosphate, and the chemical formula is a-FePO 4 ·xH 2 O (x>0).

[0014] In step S300, the first product is sintered in an air or oxygen atmosphere to form an iron phosphate precursor. In this embodiment, when the first product is continuously sintered for at least 1 hour within the temperature range of 610 °C to 670 °C, 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 batteries of 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 batteries of the present invention includes the following steps. First, in step S201, in a first temperature environment (for example, in an environment preheated to 35°C to 45°C), deionized water and iron powder are mixed to form an iron powder aqueous solution. In an embodiment, an environment preheated to 42°C is preferred, but the present invention is not limited thereto. Next, in step S202, in a second temperature environment, a first quantity of phosphoric acid is added to the iron powder aqueous solution at a constant titration rate for reaction. After reaching the second temperature, the temperature is decreased to the third temperature and maintained for the first hour. According to the technical idea of the present invention, after mixing, other compounds that release phosphate ions into the aqueous solution can also be used to titrate the iron powder aqueous solution, but the present invention is not limited thereto. In this embodiment, the concentration of phosphoric acid is 85 wt.%, and the titration rate is 10 mL / min to 40 mL / min. In another embodiment, the concentration of phosphoric acid is not limited to 85 wt.%, and the titration rate can also be changed according to actual needs, and the present invention is not limited thereto. Also, the second temperature is 60°C or lower, preferably 60°C. The third temperature is 50°C or lower, preferably 35°C. The first hour is at least 3 hours, preferably 3 hours.

[0016] In an embodiment, in step S202, it is preferable to control the titration rate of titrating phosphoric acid with a concentration of 85 wt.% into the iron powder aqueous solution so as to complete the titration within a titration time of 1 hour to 3 hours. Reacting the iron powder aqueous solution by phosphoric acid titration can be adjusted according to the reaction temperature, pH value or gelling state. Titrate and react the iron powder aqueous solution with a first quantity of phosphoric acid, and after the reaction temperature reaches 60°C, lower the temperature. After the titration of the first quantity of phosphoric acid is completed or after peptization, lower the temperature to 35°C and hold for 3 hours. The present invention is not limited thereto. Next, in step S203, lower the temperature to the fourth temperature, add a second quantity of phosphoric acid, and react the phosphoric acid with the iron powder aqueous solution for the second hour to form a first product.

[0017] In addition, for the apparatus that titrates the first quantity of phosphoric acid into the aqueous iron powder solution, it is necessary to consider safety and operability so that a large amount of hydrogen is not generated at once. FIG. 3 shows the titration apparatus used in the method for manufacturing the iron phosphate precursor for a battery according to the present invention. As shown in the figure, the titration apparatus 1 includes a tank body 10, a stirring module 20, and two supply modules 30. The tank body 10 is, for example, a reaction kettle equipped with a water jacket for temperature control, and is configured to provide a space for accommodating the aqueous iron powder solution L and performing a titration reaction. A baffle 11 is provided on the inner peripheral wall of the tank body 10, and cooperates with the stirring operation of the stirring module 20 to uniformly mix the reactants. Phosphoric acid T is titrated into the aqueous iron powder solution L by the two supply modules 30. The supply module 30 is composed of a supply pipe 31 and a peristaltic pump 32. The supply pipe 31 is fixed to the baffle 11, for example, and communicates with the bottom layer of the tank body 10. By driving the peristaltic pump 32, phosphoric acid T can be introduced into the aqueous iron powder solution L from the bottom layer of the tank body 10 at a stable titration rate. In an embodiment, it can be seen that titrating the first quantity of phosphoric acid T into the aqueous iron powder solution L is completed within 1 hour, only bubbles are generated throughout the entire process, gelation does not occur, and the operability is greatly improved. Of course, the number and arrangement method of the supply modules 30 can be changed according to actual needs, and the present invention is not limited thereto.

[0018] In this embodiment, the first product is an amorphous form of iron phosphate, and the chemical formula is a-FePO 4 ·xH 2 O (x>0). The fourth temperature is 30°C or lower, preferably 30°C. The second time is 5 to 9 hours, the weight ratio of the first quantity to the second quantity is greater than 2.5. For example, the weight ratio of the first quantity to the second quantity is 3, that is, the first quantity is 75% and the second quantity is 25%. Note that the present invention is not limited thereto.

[0019] Please refer to FIG. 4 in combination with FIG. 1. FIG. 4 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 4, 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. In step S211, after the reaction is completed in 5 to 9 hours, first grinding is performed so that the particle size of the D99 of the first product is smaller than the first length. Then, step S212 is performed. Specifically, in order to promote the reaction and further complete the reaction between phosphoric acid and iron powder, the reaction is continued for a third hour. In this embodiment, the iron powder has a specific specification (being iron powder of 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, the amorphous iron phosphate film adhering to the surface of the iron powder can be removed by appropriate polishing. As a result, the iron powder reactant can be brought into contact with phosphoric acid, so that the entire reaction can proceed more completely. Of course, in other embodiments, the first grinding operation in step S211 can also be omitted, and the present invention is not limited thereto.

[0020] In this embodiment, the first length is less than 100 μm, and the range of the third hour is 6 to 12 hours. In this embodiment, the first grinding performs a grinding operation, for example, 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). By the secondary reaction of phosphoric acid, deionized water, and iron powder, the phosphoric acid solution and iron powder can react sufficiently, effectively reducing waste of raw materials and realizing the effect of comprehensively improving the quality of the product.

[0021] 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. 5 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. 6 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. 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 a 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 pulverization is performed. In the present embodiment, the carbon source is, for example, a saccharide, an organic compound, a polymer, or a high molecular material. In some embodiments, examples of the saccharide include fructose, sucrose, lactose, galactose, etc., but the present invention is not limited thereto. Further, the high molecular 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 other compounds containing lithium atoms, or a mixture of a plurality of compounds containing lithium atoms, but the present invention is not limited thereto.

[0022] 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 the present 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 the present embodiment, the spray drying operation is performed 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, but the present invention is not limited thereto. In the present embodiment, the carbon source is mainly added to prevent particle growth 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.

[0023] In step S301, the metal compound after spray drying and the iron phosphate precursor are sintered at a high temperature. In the present embodiment, the metal compound after spray drying and the iron phosphate precursor are placed in an air or oxygen atmosphere and held at 325°C for 0.5 hour, 550°C for 0.5 hour, and 650°C for 1 hour. Finally, 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 ) is formed. 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 a metal oxide. The LiFePO 4 material containing a metal oxide can be called "nano metal oxide co-crystalline lithium iron phosphate compound (LFP-NCO)".

[0024] According to the above content, in the secondary reaction of phosphoric acid, deionized water and iron powder, phosphoric acid is added to the aqueous iron powder solution mixed with iron powder and water by a titration method. As a result, since the reaction rate between phosphoric acid and iron powder is too fast, the temperature of the aqueous solution rises too rapidly, affecting the product quality of the iron phosphate precursor, reducing the hydrogen generation rate, suppressing the occurrence of the hydration reaction, and improving safety and the operability of raw materials. Also, when forming a battery composite material by combining the manufacturing method of the iron phosphate precursor, the time required for grinding can be significantly shortened, thereby reducing the unit time and cost. 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 of raw materials and clogging of pipelines can be avoided, the temperature of the control process can be stabilized, and the difficulty of operation of the manufacturing process and the production line can also be reduced.

[0025] The following describes the method for manufacturing an iron phosphate precursor for a battery according to the present invention with reference to exemplary embodiments.

[0026] Example 1

[0027] First, prepare 9000 mL of deionized water and 2476 g of iron powder (purity 99% or more). The range of the apparent density of the iron powder is 2.3 g / cm 3 ~2.6 g / cm 3It is as follows. The maximum particle size of the iron powder is less than 212 μm, and the weight of the fine powder of the iron powder (≤ 45 μm) accounts for 21.6% of the total weight of the iron powder. Deionized water and the iron powder are mixed to form an iron powder aqueous solution, and the iron powder aqueous solution is heated to 42 °C. The first quantitative amount of 3760 g of phosphoric acid (purity 85% or more) is added to the iron powder aqueous solution at a titration rate of 37 mL / min for reaction. The reaction reaches 60 °C after about 54 minutes. When the reaction temperature reaches 60 °C or higher, cooling is performed to prevent the reaction from being too fast and the iron powder from failing to react completely with the phosphoric acid reaction. After the titration of the first quantitative amount of phosphoric acid is completed within 1 hour, the temperature is decreased to 35 °C after peptization is completed. Then, the second quantitative amount of 1467 g of phosphoric acid is directly added, stirred, and left standing for 24 hours, so that the iron powder and phosphoric acid in the aqueous solution can react completely to produce a first product. The aqueous solution containing the first product is spray-dried and sintered continuously for at least 1 hour within the temperature range of 610 °C to 670 °C to obtain an iron phosphate precursor (FePO 4 ).

[0028] Example 2

[0029] First, 9000 mL of deionized water and 2476 g of iron powder (purity 99% or more) are prepared. 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 of the iron powder (≤ 45 μm) accounts for 21.6% of the total weight of the iron powder. Deionized water and the iron powder are mixed to form an iron powder aqueous solution, and the iron powder aqueous solution is heated to 42 °C. The first quantitative amount of 3760 g of phosphoric acid (purity 85% or more) is added to the iron powder aqueous solution at a titration rate of 12.4 mL / min for reaction. After about 146 minutes, the maximum temperature of 56.9 °C is reached. After the titration of the first quantitative amount of phosphoric acid is completed within 3 hours, the temperature is decreased to 35 °C. Then, the second quantitative amount of 1467 g of phosphoric acid is directly added, stirred, and left standing for 24 hours, so that the iron powder and phosphoric acid in the aqueous solution can react completely to produce a first product. The aqueous solution containing the first product is spray-dried and sintered continuously for at least 1 hour within the temperature range of 610 °C to 670 °C to obtain an iron phosphate precursor (FePO 4) can be obtained.

[0030] Comparative Example 1

[0031] First, prepare 9000 mL of deionized water and 2476 g of iron powder (purity 99% or higher). 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 of the iron powder (≤45 μm) accounts for 21.6% of the total weight of the iron powder. Mix the deionized water and the iron powder to form an iron powder aqueous solution, and heat the iron powder aqueous solution to 42°C. Weigh 3760 g of phosphoric acid (purity 85% or higher) as the first quantitative amount, and charge it into the iron powder aqueous solution all at once for reaction. The reaction reaches 60°C after about 9 minutes. When the reaction temperature reaches 60°C or higher, the temperature is lowered to prevent the reaction from being too fast and the iron powder and phosphoric acid from not reacting completely. After the peptization is completed, the temperature is lowered to 35°C. Then, 1467 g of phosphoric acid as the second quantitative amount is directly added, stirred, and left for 24 hours, so that the iron powder and phosphoric acid in the aqueous solution can react completely to produce a first product. The aqueous solution containing the first product is spray-dried and sintered at a temperature in the range of 610°C to 670°C for at least 1 hour to obtain an iron phosphate precursor (FePO 4 ).

[0032] In the temperature-rising reaction after adding the first quantitative amount of phosphoric acid to the iron powder aqueous solution, Comparative Example 1 reaches 60°C after about 9 minutes. Example 1 reaches 60°C after about 54 minutes. Example 2 reaches the highest temperature of 56.9°C after about 146 minutes. In other words, in the reaction of titrating the first quantitative amount of phosphoric acid into the iron powder aqueous solution, the time until reaching 60°C (or the highest temperature) and the titration rate have a negative correlation.

[0033] In this embodiment, after the titration of the iron powder aqueous solution was completed within 1 hour by the first quantitative amount of phosphoric acid in Example 1, the pH value increased to a high value again. This means that the titration consumption amount of the first quantitative amount of phosphoric acid in Example 1 is complete. The change in the pH value after adding the second quantitative amount of phosphoric acid is the same. The increase in the pH value in Example 1 is superior to that in Example 2. In other embodiments, the stability of the pH value is not limited to the control by the titration rate. It should be noted that the titration rate and the total titration time of phosphoric acid can be adjusted according to actual needs and are related to the titration device.

[0034] As described above, in the method for manufacturing an iron phosphate precursor for a battery of the present invention, by controlling the specifications (standards) of the raw material iron powder, phosphoric acid is added to an iron powder aqueous solution formed by mixing iron powder and water using a titration method and a safe method. The titration time is controlled to be completed within 1 hour, and the reaction between phosphoric acid and iron powder is realized at an optimized reaction rate, achieving the purposes of improving the quality of the product, reducing raw materials and time, and suppressing the difficulty of the manufacturing operation. In addition, a carbon source as a dispersant can be added to the amorphous iron phosphate formed by the iron phosphate precursor, pulverized, the viscosity can be adjusted, and the difficulty of the manufacturing operation can be reduced. In the secondary reaction of phosphoric acid, deionized water and iron powder, phosphoric acid and iron powder react completely. By combining the manufacturing method of the iron phosphate precursor to form a battery composite material, the time required for pulverization can be significantly shortened, and the unit time and cost can be reduced. At the same time, by combining the changes of the plurality of parameters, the pH value sensitivity in the manufacturing process can be reduced, adhesion and retention of raw materials and clogging of pipelines can be avoided, the temperature in the control process can be stabilized, and the difficulty of the manufacturing process and the production line operation 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.

[0035] 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 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, phosphoric acid is added to an aqueous iron powder solution formed by mixing iron powder and water using a titration method, avoiding that the reaction rate between phosphoric acid and iron powder is too fast, and avoiding that the rise of the aqueous solution is too fast or too high, which affects the product quality of the iron phosphate precursor and that a large amount of hydrogen is rapidly generated and affects safety. Further, when the iron powder reactant has not completely reacted, the amorphous iron phosphate film adhering to the surface of the iron powder reactant can be removed by combining a pulverization process, and the iron powder reactant can contact phosphoric acid again to perform a complete reaction, effectively reducing waste of raw materials and comprehensively improving the conversion rate of the iron phosphate precursor. Furthermore, through the secondary reaction of phosphoric acid, deionized water, and iron powder, phosphoric acid and iron powder can completely react, 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 pulverization 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 clogging of pipelines can be avoided, the temperature of the control process can be stabilized, and the difficulty of operating the manufacturing process and the production line can also be reduced.

[0036] 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, but any such changes, improvements, and modifications are included in the scope of the claims of the present invention.

Description of Reference Numerals

[0037] 1: Titration device 10: Tank body 11: Baffle 20: Stirring module 30: Supply module 31: Supply pipe 32: Peristaltic pump L: Aqueous iron powder solution T: Phosphoric acid 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) preparing iron powder, the apparent density of the iron powder being 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) providing phosphoric acid, said phosphoric acid reacting with said 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 in the step (c), sintering is continuously performed for at least 1 hour within a temperature range of 610° C. to 670° C.

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% by 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) mixing deionized water and the iron powder in a first temperature environment to form an aqueous iron powder solution; Step (b12) of adding a first amount of the phosphoric acid to the aqueous iron powder solution at a constant titration rate in a second temperature environment to react with the aqueous iron powder solution, 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 amount of the phosphoric acid, and reacting the phosphoric acid with the aqueous iron powder solution continuously for a second period of time to form 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 greater than 2.

5.

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 35° C. or less.

9. 7. The method for producing an iron phosphate precursor for batteries according to claim 6, wherein the concentration of the phosphoric acid is 85 wt. %, and the titration rate is in the range of 10 mL / min to 40 mL / min.

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

11. The step (b) A step (b21) of performing a first grinding, the first product having a particle size D99 smaller than a first length; and (b22) continuously reacting for a third time.

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

13. 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 carrying out a second grinding; 12. The method for producing an iron phosphate precursor for batteries according to claim 11, further comprising: (b32) performing a spray drying operation on 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.

14. The method for producing an iron phosphate precursor for batteries according to claim 13, wherein 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 300Hz to 400Hz.

15. The method for producing an iron phosphate precursor for batteries according to claim 13, wherein the second length is 1 μm to 10 μm.

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

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

18. 18. The method for preparing an iron phosphate precursor for batteries according to claim 17, 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).

19. 18. The method of claim 17, wherein the step (c) includes 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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