A method for synthesizing phosphogypsum-modified lithium iron phosphate materials

Abstract

This invention discloses a method for synthesizing phosphogypsum-modified lithium iron phosphate material, comprising the following steps: 1) preparing a calcium sulfate aqueous solution using phosphogypsum; 2) adding lithium iron phosphate and thoroughly mixing with the calcium sulfate aqueous solution prepared in step 1) to obtain a composite; 3) subjecting the composite obtained in step 2) to high-temperature calcination at 600–900°C for 4–6 hours, obtaining a sample after high-temperature calcination; 4) subjecting the sample obtained after high-temperature calcination in step 3) to low-temperature calcination at 400–450°C for 1–2 hours. Calcium sulfate can be thoroughly mixed with lithium iron phosphate to form a composite, achieving modification of lithium iron phosphate. The resulting product exhibits high performance in lithium-ion batteries, achieving advantages such as high-rate discharge and good cycle stability.

Description

Technical Field

[0001] This invention relates to the technical field of modified lithium iron phosphate material synthesis methods, and particularly to a method for synthesizing phosphogypsum-modified lithium iron phosphate material. Background Technology

[0002] With increasing global attention to environmental protection and new energy sources, lithium-ion batteries have received growing attention due to their high energy density and good low-temperature performance. Among them, cathode materials are one of the most critical components of lithium-ion batteries, directly determining their performance and lifespan. Therefore, developing low-cost, high-efficiency, and high-cycle-stability cathode materials has become one of the core research directions in the field of lithium-ion batteries.

[0003] Currently, lithium iron phosphate (LFP) is a highly regarded cathode material with advantages such as high energy density, low cost, and environmental friendliness. However, LFP has low electronic conductivity, which limits the improvement of lithium-ion battery performance. Therefore, modification is necessary. Developing an efficient modification method that can improve the conductivity of LFP while maintaining its excellent performance is of great significance to the field of lithium-ion batteries. Summary of the Invention

[0004] This invention provides a method for synthesizing phosphogypsum-modified lithium iron phosphate materials to solve the problems mentioned in the background art.

[0005] The solution of the present invention is:

[0006] A method for synthesizing phosphogypsum-modified lithium iron phosphate material includes the following steps:

[0007] 1) Prepare calcium sulfate aqueous solution using phosphogypsum, with a concentration of 0.008586–0.0111 g / ml;

[0008] 2) The lithium iron phosphate solution prepared in 1) is thoroughly mixed to obtain the complex;

[0009] 3) The composite obtained in 2) is subjected to high-temperature calcination at a temperature of 600-900℃ for 4-6 hours. After the high-temperature calcination is completed, the sample is obtained.

[0010] 4) The sample obtained after high-temperature calcination in 3) is then subjected to low-temperature roasting at a temperature of 400-450℃ for 1-2 hours.

[0011] As a preferred technical solution, the concentration of the calcium sulfate aqueous solution in step 1) is 0.01 g / ml.

[0012] As a preferred technical solution, the amount of lithium iron phosphate added in step 2) is 10 to 11 times the mass of the prepared calcium sulfate aqueous solution.

[0013] As a preferred technical solution, the lithium iron phosphate and calcium sulfate aqueous solution in step 2) are mechanically mixed to obtain a complex.

[0014] As a preferred technical solution, in step 2), lithium iron phosphate and calcium sulfate aqueous solution are added to a spray dryer and mixed. The liquid material is then fed into a pressure atomizer at a high pressure of 0.5 to 2 MPa and atomized into small droplets. After atomization, the droplets come into contact with hot air and the drying process is completed rapidly within 30 seconds, resulting in a uniform fine particle composite.

[0015] As a preferred technical solution, the composite obtained in 2) is subjected to high-temperature calcination at a temperature of 700–800°C.

[0016] As a preferred technical solution, the high-temperature calcination in step 3) is carried out using a tubular furnace.

[0017] The addition of phosphogypsum can help stabilize the crystal structure of lithium iron phosphate, preventing structural changes or deactivation, thereby improving battery cycle life. Simultaneously, the calcium ions in phosphogypsum can provide additional conductive pathways, improving the charge transport efficiency of lithium iron phosphate materials and thus enhancing battery performance. Therefore, a small amount of phosphogypsum can be used to modify lithium iron phosphate, improving its electrochemical performance, including increasing its discharge capacity and cycle life. In addition, phosphogypsum also contains trace amounts of other ions, such as PO42-. 3- ,F - When modifying lithium iron phosphate with anions, a complex is prepared. This complex is a lithium iron phosphate / calcium sulfate complex, which improves the stability of the crystal structure, thereby enhancing the electrochemical stability of the material, widening the diffusion channels of Li+, and improving the high-rate performance of the material.

[0018] A method for synthesizing phosphogypsum-modified lithium iron phosphate material using the above technical solution includes: 1) preparing a calcium sulfate aqueous solution using phosphogypsum, with a concentration of 0.008586–0.0111 g / ml; 2) thoroughly mixing lithium iron phosphate with the calcium sulfate aqueous solution prepared in 1) to obtain a composite; 3) subjecting the composite obtained in 2) to high-temperature calcination at 600–900℃ for 4–6 hours, and obtaining a sample after high-temperature calcination; 4) subjecting the sample obtained after high-temperature calcination in 3) to low-temperature roasting at 400–450℃ for 1–2 hours.

[0019] Advantages of this invention:

[0020] 1. Calcium sulfate can be fully mixed with lithium iron phosphate to form a complex, thereby modifying lithium iron phosphate. The resulting product exhibits high performance in lithium-ion batteries, with advantages such as high-rate discharge and good cycle stability.

[0021] 2. The main raw material used in this method is phosphogypsum, which is a solid waste generated in the wet phosphoric acid process. Therefore, it has the characteristics of low production cost and simple operation. Attached Figure Description

[0022] Figure 1 The product rate performance curve is shown in Embodiment 1 of the invention. Detailed Implementation

[0023] This invention provides a method for synthesizing phosphogypsum-modified lithium iron phosphate materials.

[0024] To make the technical means, creative features, objectives and effects of this invention easier to understand, the invention will be further described below with reference to specific embodiments.

[0025] Example 1:

[0026] (1) Preparation of calcium sulfate aqueous solution using phosphogypsum: The specific preparation process is to take 10g of phosphogypsum (W(CaSO4*2H2O)=85%), add it to 1000ml of deionized water, and stir until it is completely dissolved to obtain calcium sulfate aqueous solution;

[0027] (2) Add lithium iron phosphate at a mass of 10 times that of the calcium sulfate aqueous solution prepared in step (1) and mix thoroughly with the calcium sulfate aqueous solution prepared in step (1) to obtain lithium iron phosphate / calcium sulfate complex;

[0028] (3) The composite obtained in step (2) is subjected to high-temperature calcination at a temperature of 700°C for 4 hours. After the high-temperature calcination is completed, a sample is obtained.

[0029] (4) The sample obtained after high-temperature calcination in step (3) is then subjected to low-temperature roasting at a temperature of 450°C for 2 hours.

[0030] Through the above operations, after completing all the steps, a phosphogypsum-modified lithium iron phosphate material was obtained, which exhibited excellent performance such as high-rate discharge and cycle stability.

[0031] Example 2:

[0032] (1) Preparation of calcium sulfate aqueous solution using phosphogypsum: The specific preparation process is to take 9.1g of phosphogypsum (W(CaSO4*2H2O)=85%), add it to 1000ml of deionized water, and stir until it is completely dissolved to obtain calcium sulfate aqueous solution;

[0033] (2) Add lithium iron phosphate at a mass of 10 times that of the calcium sulfate aqueous solution prepared in step (1) and mix thoroughly with the calcium sulfate aqueous solution prepared in step (1) to obtain lithium iron phosphate / calcium sulfate complex;

[0034] (3) The composite obtained in step (2) is subjected to high-temperature calcination at a temperature of 700°C for 4 hours. After the high-temperature calcination is completed, a sample is obtained.

[0035] (4) The sample obtained after high-temperature calcination in step (3) is then subjected to low-temperature roasting at a temperature of 450°C for 2 hours.

[0036] Through the above operations, after completing all the steps, a phosphogypsum-modified lithium iron phosphate material was obtained, which also showed excellent performance such as high-rate discharge and cycle stability, but its performance was lower than that of Specific Example 1.

[0037] Example 3:

[0038] (1) Preparation of calcium sulfate aqueous solution using phosphogypsum: The specific preparation process is to take 11.1g of phosphogypsum (W(CaSO4*2H2O)=85%), add it to 1000ml of deionized water, and stir until it is completely dissolved to obtain calcium sulfate aqueous solution;

[0039] (2) Add lithium iron phosphate at a mass of 10 times that of the calcium sulfate aqueous solution prepared in step (1) and mix thoroughly with the calcium sulfate aqueous solution prepared in step (1) to obtain lithium iron phosphate / calcium sulfate complex;

[0040] (3) The composite obtained in step (2) is subjected to high-temperature calcination at a temperature of 700°C for 4 hours. After the high-temperature calcination is completed, a sample is obtained.

[0041] (4) The sample obtained after high-temperature calcination in step (3) is then subjected to low-temperature roasting at a temperature of 450°C for 2 hours.

[0042] Through the above operations, after completing all the steps, a phosphogypsum-modified lithium iron phosphate material was obtained, which also showed excellent performance such as high-rate discharge and cycle stability, but its performance was lower than that of Specific Example 1.

[0043] Example 4:

[0044] (1) Preparation of calcium sulfate aqueous solution using natural gypsum: The specific preparation process is to take 8.586g of natural gypsum (W(CaSO4*2H2O)=99%), add it to 1000ml of deionized water, and stir until it is completely dissolved to obtain calcium sulfate aqueous solution;

[0045] 2) Add lithium iron phosphate at a mass of 10 times that of the calcium sulfate aqueous solution prepared in step (1) and mix thoroughly with the calcium sulfate aqueous solution prepared in step (1) to obtain lithium iron phosphate / calcium sulfate complex;

[0046] (3) The composite obtained in step (2) is subjected to high-temperature calcination at a temperature of 700°C for 4 hours. After the high-temperature calcination is completed, a sample is obtained.

[0047] (4) The sample obtained after high-temperature calcination in step (3) is then subjected to low-temperature roasting at a temperature of 450°C for 2 hours.

[0048] Through the above operations, after completing all the steps, a phosphogypsum-modified lithium iron phosphate material was obtained, which also showed excellent performance such as high-rate discharge and cycle stability, but its performance was lower than that of Specific Example 1.

[0049] The average discharge specific capacity of the products obtained in Examples 1 to 4 is shown in Table 1; the rate performance curve of the product in Example 1 is shown in Table 4. Figure 1 Examples 1-3 investigate the effect of calcium ion concentration in phosphogypsum on the electrical properties of the synthesized product; Example 4 investigates the effect of calcium ion concentration in natural gypsum on the electrical properties of the synthesized product.

[0050] Table 1. Average discharge specific capacity of products obtained from specific examples 1-4

[0051] Example 1 Example 2 Example 3 Example 4 0.1C average discharge specific capacity / mAh / g 164 156 158 159 0.2C average discharge specific capacity / mAh / g 140 136 138 138 0.5C average discharge specific capacity / mAh / g 125 121 122 123 1C average discharge specific capacity / mAh / g 100 96 98 97

[0052] As can be seen from the above, the product prepared with a calcium ion concentration of 0.05 mol / L exhibits the best electrical properties. Additionally, phosphogypsum contains trace amounts of other ions, such as PO42-. 3 -,F - These methods can also improve the electrochemical stability of crystals, broaden the diffusion channels of Li+, and enhance the high-rate performance of materials.

[0053] Example 5:

[0054] (1) Preparation of calcium sulfate aqueous solution using phosphogypsum: The specific preparation process is to take 10g of phosphogypsum (W(CaSO4*2H2O)=85%), add it to 1000ml of deionized water, and stir until it is completely dissolved to obtain calcium sulfate aqueous solution;

[0055] (2) Add lithium iron phosphate at a mass of 10 times that of the calcium sulfate aqueous solution prepared in step (1) and mix thoroughly with the calcium sulfate aqueous solution prepared in step (1) to obtain lithium iron phosphate / calcium sulfate complex;

[0056] (3) The composite obtained in step (2) is subjected to high-temperature calcination at a temperature of 600°C for 4 hours. After the high-temperature calcination is completed, a sample is obtained.

[0057] (4) The sample obtained after high-temperature calcination in step (3) is then subjected to low-temperature roasting at a temperature of 400°C for 2 hours.

[0058] Through the above operations, after completing all the steps, a phosphogypsum-modified lithium iron phosphate material was obtained, which also showed excellent performance such as high-rate discharge and cycle stability, but its performance was lower than that of Specific Example 1.

[0059] Example 6:

[0060] (1) Preparation of calcium sulfate aqueous solution using phosphogypsum: The specific preparation process is to take 10g of phosphogypsum (W(CaSO4*2H2O)=85%), add it to 1000ml of deionized water, and stir until it is completely dissolved to obtain calcium sulfate aqueous solution;

[0061] (2) Add lithium iron phosphate at a mass of 10 times that of the calcium sulfate aqueous solution prepared in step (1) and mix thoroughly with the calcium sulfate aqueous solution prepared in step (1) to obtain lithium iron phosphate / calcium sulfate complex;

[0062] (3) The composite obtained in step (2) is subjected to high-temperature calcination at a temperature of 900°C for 4 hours. After the high-temperature calcination is completed, a sample is obtained.

[0063] (4) The sample obtained after high-temperature calcination in step (3) is then subjected to low-temperature roasting at a temperature of 400°C for 2 hours.

[0064] Through the above operations, after completing all the steps, a phosphogypsum-modified lithium iron phosphate material was obtained, which also showed excellent performance such as high-rate discharge and cycle stability, but its performance was lower than that of Example 1.

[0065] The average discharge specific capacity of the products obtained in Examples 1, 5, and 6 is shown in Table 2.

[0066] Table 2. Average discharge specific capacity of products obtained from specific examples 1, 5, and 6

[0067] Example 1 Example 5 Example 6 0.1C average discharge specific capacity / mAh / g 164 151 159 0.2C average discharge specific capacity / mAh / g 140 132 136 0.5C average discharge specific capacity / mAh / g 125 118 121 1C average discharge specific capacity / mAh / g 100 93 96

[0068] As shown in Table 2, both excessively high and low calcination temperatures will affect the electrochemical properties of the final product. Specifically, excessively high and low temperatures will prevent calcium ions from entering the corresponding crystal lattice effectively, resulting in insufficient calcium ion concentration and thus failing to achieve the best modification effect.

[0069] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for synthesizing phosphogypsum-modified lithium iron phosphate material, characterized in that, Includes the following steps: 1) Prepare calcium sulfate aqueous solution using phosphogypsum, with a concentration of 0.008586–0.0111 g / ml; 2) The lithium iron phosphate solution prepared in 1) is thoroughly mixed to obtain the complex; 3) The composite obtained in 2) is subjected to high-temperature calcination at a temperature of 600-900℃ for 4-6 hours. After the high-temperature calcination is completed, the sample is obtained. 4) The sample obtained after high-temperature calcination in 3) is then subjected to low-temperature roasting at a temperature of 400-450℃ for 1-2 hours. In step 2), the amount of lithium iron phosphate added is 10 to 11 times the mass of the prepared calcium sulfate aqueous solution; in step 2), the lithium iron phosphate and calcium sulfate aqueous solution are mechanically mixed to obtain a complex; in step 2), the lithium iron phosphate and calcium sulfate aqueous solution are added to a spray dryer and mixed, and the liquid is sent into a pressure atomizer at a high pressure of 0.5 to 2 MPa to atomize into small droplets. After atomization, the droplets come into contact with hot gas and the drying process is completed rapidly within 30 seconds, resulting in a uniform fine particle complex.

2. The method for synthesizing a phosphogypsum-modified lithium iron phosphate material as described in claim 1, characterized in that: The concentration of the calcium sulfate aqueous solution in 1) is 0.01 g / ml.

3. The method for synthesizing a phosphogypsum-modified lithium iron phosphate material as described in claim 1, characterized in that: The high-temperature calcination in step 3) is carried out using a tubular furnace.

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