Preparation method for synthesizing ferric phosphate from ferric chloride

Abstract

The invention discloses a preparation method for synthesizing ferric phosphate from ferric chloride, and relates to the technical field of preparation of ferric phosphate, the technical key point of the preparation method comprises the following steps: S1, dissolving and heating: adding ferric chloride and ammonium dihydrogen phosphate into a three-neck flask, pouring deionized water, stirring and dissolving, heating to 100 DEG C, and keeping for 3 hours; s2, pH adjustment: gradually adding ammonia water, controlling the pH value to 4-5, stopping heating, continuously and slowly adding ammonia water until the pH value reaches 5, heating to 100 DEG C, and keeping the temperature for 2 hours; and S3, washing: after the reaction is finished, washing the precipitate with warm water for three times. And S4, dehydration treatment: dehydrating the dried iron phosphate in a muffle furnace. And S5, preparation of lithium iron phosphate: mixing iron phosphate with a lithium source, carrying out ball milling and spray drying, and carrying out a sintering reaction at a high temperature to prepare the lithium iron phosphate. The method is simple and convenient to operate through mild liquid phase reaction, high-purity iron phosphate can be generated, and the method has relatively high production efficiency and low energy consumption.

Description

Technical Field

[0001] The invention relates to the technical field of ferric phosphate preparation, and in particular to a method for preparing ferric phosphate by synthesizing ferric chloride. Background Art

[0002] Iron phosphate (FePO4) is an important inorganic material, which is widely used in many fields due to its unique physical and chemical properties, especially in lithium-ion batteries, catalysts, pigments, adsorbents, etc. In recent years, with the rapid development of the new energy industry, iron phosphate has received more and more attention as a precursor of lithium iron phosphate (LiFePO4) battery cathode material.

[0003] The existing method for preparing iron phosphate has the following technical problems:

[0004] Harsh reaction conditions: Some preparation methods used in existing technologies (such as solid phase method or hydrothermal method) require higher temperature or pressure, which increases the complexity and energy consumption of the equipment and is not conducive to large-scale production.

[0005] Product purity is low: The reaction control in the existing technology is not precise enough, which easily leads to a high impurity content in the iron phosphate, thereby affecting its performance as a positive electrode material for lithium iron phosphate batteries.

[0006] Low energy utilization rate: Some existing technical methods have low energy utilization rate during sintering or heating, resulting in excessively high process energy consumption, which is not conducive to energy conservation and environmental protection. Summary of the invention

[0007] The purpose of the present invention is to solve the above problems and provide a method for preparing ferric phosphate by using ferric chloride.

[0008] In order to achieve the above object, the technical scheme of the present invention is as follows: a method for preparing ferric phosphate by synthesizing ferric chloride, comprising the following steps:

[0009] S1. Dissolving and heating: Add ferric chloride and ammonium dihydrogen phosphate into a three-necked flask, then pour in deionized water to stir and dissolve, turn on the heating device, heat the solution to 100° C., and maintain this temperature for 3 hours;

[0010] S2. pH adjustment: gradually add ammonia water to start adjusting the pH value of the solution. With the addition of ammonia water, the pH value of the solution will gradually rise. When the pH value reaches 4-5, stop heating and continue to slowly add ammonia water. When the pH value reaches 5, stop adding ammonia water. Then turn on the heating device to heat the solution to 100° and keep this temperature for 2 hours.

[0011] S3, washing: after the heat preservation reaction is completed, use warm water to wash, separate the precipitate from the solution, and wash it three times with 1L of warm water;

[0012] S4, drying: placing the wet ferric phosphate material into a drying oven and drying it at 120°C;

[0013] S5, dehydration treatment: placing the dried iron phosphate into a muffle furnace for dehydration treatment;

[0014] S6. Preparation of lithium iron phosphate: Mix the iron phosphate with a lithium source, evenly disperse them through a ball milling process, then spray dry them, and finally perform a sintering reaction at a high temperature to prepare lithium iron phosphate.

[0015] Preferably, the mass ratio of the ferric chloride to diammonium hydrogen phosphate and deionized water is 2.7:1:11.5.

[0016] Compared with the prior art, this solution has the following beneficial effects:

[0017] Mild reaction conditions: The liquid phase method is used, the reaction conditions are mild, the operation is simple, and it is suitable for large-scale industrial production.

[0018] High-purity products: Through strict pH adjustment and temperature control, the purity of ferric phosphate products is ensured and the generation of impurities is reduced.

[0019] Higher yield and uniform dispersion: Ball milling and spray drying processes help to improve the uniform dispersion of iron phosphate and lithium source, and enhance the electrochemical performance of the final product.

[0020] Strong repeatability: The conditions of each step are clear and easy to control, which is conducive to maintaining consistency in product performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is a discharge curve diagram of lithium iron phosphate prepared in Example 1 of the present invention;

[0022] Figure 2 is a discharge curve diagram of lithium iron phosphate prepared in Example 2 of the present invention;

[0023] Figure 3 This is a discharge curve diagram of the lithium iron phosphate prepared in Example 3 of the present invention. DETAILED DESCRIPTION

[0024] In order to enable those skilled in the art to better understand the solution of the present invention, the technical solution of the present invention will be further described in detail below in conjunction with the embodiments of the present invention and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0025] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present invention can be combined with each other. The present invention will be described in detail below in conjunction with the embodiments.

[0026] Embodiment 1:

[0027] 1 Experimental materials

[0028] Table 1 Material list

[0029] Sample name Weight / g Remark Ferric chloride 310.28 Ammonium dihydrogen phosphate 115.02 Deionized water 1320 ammonia 160 For pH adjustment

[0030] 2 Preparation process

[0031] 1) Add 310.28 g of ferric chloride, 115.02 g of ammonium dihydrogen phosphate and 1320 mL of deionized water, put into a three-necked flask and stir, turn on the heating temperature and control it at 100° for 3 hours.

[0032] 2) Gradually add ammonia water to start adjusting the pH value of the solution. With the addition of ammonia water, the pH value of the solution will gradually rise. When the pH value reaches 4-5, stop heating and continue to slowly add ammonia water. When the pH value reaches 5, stop adding ammonia water. At this time, the amount of ammonia water is 160g; then turn on the heating device to heat the solution temperature to 100° and maintain this temperature for 2 hours;

[0033] 3) After the reaction is completed, use warm water (40-50°) to wash, separate the precipitate from the solution, and wash it three times with 1L of warm water;

[0034] 4) placing the wet ferric phosphate material into a drying oven and drying it at 120°C;

[0035] 5) The dried ferric phosphate was placed in a muffle furnace (600°, 4 h) for dehydration treatment, and 98 g of material was collected. The dehydration rate was measured to be 19.5%;

[0036] 6) Ingredients (ratio): Iron phosphate is mixed with a lithium source, evenly dispersed by ball milling, spray dried, and finally sintered at high temperature to prepare lithium iron phosphate.

[0037] 3 Electrochemical test

[0038] Table 2 Battery performance test table (voltage range 2.5-4.2V)

[0039]

[0040] 4 Physical properties

[0041] Table 3 Battery physical properties

[0042]

[0043] 5. Discharge curve

[0044] like Figure 1 As shown, the lithium iron phosphate battery prepared this time has a battery capacity of 160mAh / g at a discharge rate of 0.2C. At the same time, it can still maintain a high capacity at a high rate of discharge, with small capacity attenuation. The operating voltage of the battery remains stable, and the battery discharge curve maintains a long stable voltage platform during the discharge process.

[0045] Embodiment 2:

[0046] The experimental materials and preparation method of this example are the same as those of Example 1. However, there is a difference in the dehydration treatment stage. This time, 100 g of material was collected and the dehydration rate was measured to be 20%.

[0047] 6 Electrochemical test

[0048] Table 4 Battery performance test table (voltage range 2.5-4.2V)

[0049]

[0050] 7 Physical properties

[0051] Table 5 Battery physical properties

[0052]

[0053] 8Discharge curve diagram:

[0054] like Figure 2 As shown, the lithium iron phosphate battery prepared this time is not much different from that of Example 1. At a discharge rate of 0.2C, the battery capacity has reached 160mAh / g. At the same time, it can still maintain a high capacity during high-rate discharge, with little capacity decay. The operating voltage of the battery remains stable, and the battery discharge curve maintains a relatively long stable voltage platform during the discharge process.

[0055] Embodiment 3:

[0056] The experimental materials and preparation method of this example are the same as those of Example 1. The dehydration treatment stage is also the same, this time the material collected is 98g, and the measured dehydration rate is 19.5%.

[0057] 9 Electrochemical test

[0058] Table 6 Battery performance test table (voltage range 2.5-4.2V)

[0059]

[0060] 10 Physical properties

[0061] Table 7 Battery physical properties

[0062]

[0063] 11Discharge curve diagram:

[0064] As shown in Table 6 and Figure 3 As shown, the prepared lithium iron phosphate battery is slightly inferior to Example 1 and Example 2 in terms of battery capacity. At a discharge rate of 0.2C, the battery capacity is less than 160mAh / g, but its capacity decay is small at different discharge rates. At the same time, the operating voltage of the battery can remain stable, and the battery discharge curve can maintain a relatively long stable voltage platform during the discharge process.

[0065] The above specific embodiments are merely explanations of the present invention and are not limitations of the present invention. After reading this specification, those skilled in the art may make modifications to the embodiments without any creative contribution as needed. However, such modifications are protected by the patent law as long as they are within the scope of the claims of the present invention.

Claims

1. A method for preparing ferric phosphate by using ferric chloride, characterized in that: The following steps are involved: S1. Dissolving and heating: Add ferric chloride and ammonium dihydrogen phosphate into a three-necked flask, then pour in deionized water to stir and dissolve, turn on the heating device, heat the solution to 100° C., and maintain this temperature for 3 hours; S2. pH adjustment: gradually add ammonia water to start adjusting the pH value of the solution. With the addition of ammonia water, the pH value of the solution will gradually rise. When the pH value reaches 4-5, stop heating and continue to slowly add ammonia water. When the pH value reaches 5, stop adding ammonia water. Then turn on the heating device to heat the solution to 100° and keep this temperature for 2 hours. S3, washing: after the heat preservation reaction is completed, use warm water to wash, separate the precipitate from the solution, and wash it three times with 1L of warm water; S4, drying: placing the wet ferric phosphate material into a drying oven and drying it at 120°C; S5, dehydration treatment: placing the dried iron phosphate into a muffle furnace for dehydration treatment; S6. Preparation of lithium iron phosphate: Mix the iron phosphate with a lithium source, evenly disperse them through a ball milling process, then spray dry them, and finally perform a sintering reaction at a high temperature to prepare lithium iron phosphate.

2. The method for preparing ferric phosphate from ferric chloride according to claim 1 is characterized in that the mass ratio of the ferric chloride to diammonium phosphate and deionized water is: 2.7:1:11.5。

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