A method for synthesizing carbon-coated sodium iron pyrophosphate phosphate based on a microwave method

Abstract

The application discloses a method for synthesizing carbon-coated sodium iron pyrophosphate phosphate based on a microwave method and belongs to the technical field of sodium ion battery positive electrode materials. The steps are as follows: 1) dissolving an iron source, a phosphorus source, a sodium source and a complexing agent in water to obtain a mixed aqueous solution; 2) subjecting the prepared mixed aqueous solution obtained in the step 1) to microwave treatment under the protection of an inert atmosphere, wherein the heating rate of the microwave treatment is 100-300 DEG C / min, and the microwave treatment time is 1-6 min; 3) after the reaction is completed, post-treatment is performed to obtain the carbon-coated sodium iron pyrophosphate phosphate. The method has the advantages of simple process, few steps, extremely short synthesis time, high efficiency, no need of high-temperature calcination, low energy consumption, and the like. The obtained carbon-coated sodium iron pyrophosphate phosphate is used as a sodium ion battery positive electrode material and exhibits high energy density and good cycle stability.

Description

Technical Field

[0001] This invention belongs to the field of sodium ion cathode material technology, specifically relating to a method for synthesizing carbon-coated iron sodium pyrophosphate based on microwave method. Background Technology

[0002] The rapid increase in the use of lithium-ion batteries has led to a shortage of lithium resources. In contrast, sodium is abundant, widely distributed, and inexpensive. Therefore, sodium-ion batteries have received widespread attention as a substitute for lithium-ion batteries.

[0003] In sodium-ion battery systems, the cathode material is the most critical factor affecting the battery's energy density. Among them, sodium iron pyrophosphate (Na4Fe3(PO4)2P2O7) is one of the most commercially promising cathode materials for sodium-ion batteries due to its strong structural stability, excellent rate performance, and cycle performance.

[0004] The synthesis of sodium iron pyrophosphate cathode materials is a complex material system, commonly using solid-state synthesis or sol-gel methods. Solid-state synthesis involves preparing the cathode material for sodium-ion batteries through a solid-state reaction at high temperatures. Typically, appropriate proportions of raw materials are mixed together in solid form and then calcined at high temperatures to form the desired cathode material. Its advantages include mature equipment and high production capacity; however, the disadvantages are that the resulting materials generally have poor performance and consistency. Sol-gel synthesis is typically used to prepare cathode materials with high specific surface area and good electrochemical performance. The sol-gel process involves converting a metal-organic or inorganic compound into a sol through a solution, then dehydrating it under certain conditions (such as heating). The fluid sol gradually becomes viscous, forming a slightly elastic solid gel. The gel is then dried and calcined to obtain the nanoscale product. Although the cathode material obtained by the sol-gel process has good performance, the reaction rate is slow, usually requiring a long time, and it also requires high-temperature calcination, resulting in high energy consumption and low efficiency, which is not conducive to industrial applications. Summary of the Invention

[0005] The purpose of this invention is to provide a method for synthesizing carbon-coated iron pyrophosphate sodium based on microwave method. This method is simple, has few steps, extremely short synthesis time, high efficiency, and does not require high-temperature calcination, resulting in low energy consumption. The obtained carbon-coated iron pyrophosphate sodium exhibits high energy density and good cycle stability when used as a cathode material for sodium-ion batteries.

[0006] To solve the above-mentioned technical problems, the present invention adopts the following technical solution:

[0007] A method for synthesizing carbon-coated iron pyrophosphate sodium based on microwave method is provided, comprising the following steps:

[0008] 1) Dissolve the iron source, phosphorus source, sodium source and complexing agent in water to prepare a mixed aqueous solution;

[0009] 2) The mixed aqueous solution prepared in step 1) is subjected to microwave treatment under an inert atmosphere, wherein the heating rate of microwave treatment is 100-300℃ / min and the microwave treatment time is 1-6min.

[0010] 3) After the reaction is complete, post-processing yields carbon-coated iron pyrophosphate sodium.

[0011] According to the above scheme, in step 1), the iron salt, phosphorus source, sodium source and complexing agent are all water-soluble.

[0012] According to the above scheme, in step 1), the molar ratio of Fe element and complexing agent in the iron source is 1:1 to 2.

[0013] According to the above scheme, in step 1), the iron element in the iron source, the phosphorus element in the phosphorus source, and the sodium element in the sodium source are added according to the stoichiometric ratio in Na4Fe3(PO4)2P2O7.

[0014] According to the above scheme, in step 1), the concentration of Fe element in the iron source in the mixed aqueous solution is 0.8-1.2 mol / L.

[0015] According to the above scheme, in step 1), the iron source is selected from ferrous sulfate, ferric chloride, ferrous acetate, ferric nitrate, ferric bromide, ferric iodide, and ferric fluoride; the phosphorus source is selected from phosphoric acid; the sodium source is selected from sodium carbonate, sodium dihydrogen phosphate, and sodium oxalate; and the complexing agent is selected from sodium aminotriacetate (NTA), ethylenediaminetetraacetic acid, diethylenetriaminepentacarboxylic acid, glucose, sucrose, oxalic acid, citric acid, and tartaric acid.

[0016] According to the above scheme, in step 2), the power of microwave processing is 600-800W.

[0017] According to the above scheme, in step 2), the microwave treatment time is 3-5 minutes.

[0018] According to the above scheme, in step 2), the inert atmosphere protection is nitrogen protection.

[0019] According to the above scheme, in step 3), the post-processing is as follows: after the reaction is completed, the mixture is cooled, and then solid-liquid separation is performed. The separated solid product is then washed and dried.

[0020] The beneficial effects of this invention are as follows:

[0021] This invention discloses a microwave-based method for synthesizing carbon-coated iron pyrophosphate sodium. The method involves dissolving soluble iron salt, phosphorus source, sodium source, and complexing agent in water, mixing them, and then subjecting the mixture to microwave treatment. This allows for the one-step synthesis of carbon-coated iron pyrophosphate sodium within 6 minutes. This method features low raw material costs, a simple process, few steps, extremely short synthesis time, high efficiency, and eliminates the need for high-temperature calcination, resulting in low energy consumption. It is environmentally friendly, safe, and non-toxic, making it suitable for large-scale production. The resulting carbon-coated iron pyrophosphate sodium, when used as a cathode material in sodium-ion batteries, exhibits high energy density and good cycle stability, demonstrating broad application prospects. Attached Figure Description

[0022] Figure 1 The image shows the SEM image of the composite sodium iron phosphate prepared in Example 1.

[0023] Figure 2 The image shows the XRD pattern of the composite sodium iron phosphate prepared in Example 1.

[0024] Figure 3 The image shows the electrical properties of the composite sodium iron phosphate prepared in Example 1.

[0025] Figure 4 The image shows the SEM image of the composite sodium iron phosphate prepared in Example 2.

[0026] Figure 5 The image shows the XRD pattern of the composite sodium iron phosphate prepared in Example 2.

[0027] Figure 6 The image shows the electrical properties of the composite sodium iron phosphate prepared in Example 2. Detailed Implementation

[0028] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0029] Example 1

[0030] This embodiment provides a method for synthesizing carbon-coated iron pyrophosphate sodium based on microwave method, including the following steps:

[0031] A mixed aqueous solution was prepared by mixing iron source, phosphorus source, sodium source, and complexing agent with water according to the elemental molar ratio Fe:Na:P:complexing agent = 3:4:4:3. The Fe source was ferrous acetate, the Na source was sodium acetate, the P source was phosphoric acid, and the complexing agent was citric acid. The molar concentration of Fe in the mixed aqueous solution was 1 mol / L. The solution was placed in a microwave oven under a nitrogen atmosphere and microwaved at a power of 700 W and a heating rate of 170 °C / min for 5 min. Afterward, it was cooled to room temperature with the oven, and solid-liquid separation was performed. The separated solid product was washed three times with hot water, filtered, and dried to obtain carbon-coated iron pyrophosphate sodium.

[0032] The obtained positive electrode material was subjected to half-cell charge-discharge testing. The method was as follows: CR2032 button cells were assembled in an argon-filled glove box with sodium metal sheets as the negative electrode, and glass fiber membrane (GF / AWhat-man) was used as the separator. The electrolyte was a mixture of NP-009 (1M NaPF6 in (PC) with 5% (FEC)) with a slurry ratio of NFPP:SP:PVDF = 8:1:1. The mixture was coated on carbon-coated aluminum foil and dried at 60°C for ten hours. The active material loading was approximately 3.52 mg / cm³. -2 Test: After resting for 4 hours, the voltage range of the multiplier (0.1C) is 2.0V-4.6V.

[0033] Figure 1-3 The images show the SEM, XRD, and electrical properties of the composite material prepared in Example 1.

[0034] The figure shows that the material synthesized by the microwave method has uniform and small primary particles in the range of 50-100 nm, and good dispersibility, which is beneficial to the material's performance. XRD shows characteristic peaks consistent with the standard card for sodium iron pyrophosphate. The charging capacity is 111 mAh / g and the discharging capacity is 99 mAh / g at 0.1C (1C = 129 mAh).

[0035] Example 2

[0036] This embodiment provides a method for synthesizing carbon-coated iron pyrophosphate sodium based on microwave method, including the following steps:

[0037] A mixed aqueous solution was prepared by mixing iron source, phosphorus source, sodium source, and complexing agent with water according to the elemental molar ratio Fe:Na:P:complexing agent = 3:4:4:4.5. The Fe source was ferrous sulfate, the Na source was sodium oxalate, the P source was phosphoric acid, and the complexing agent was tartaric acid. The molar concentration of Fe in the mixed aqueous solution was 1 mol / L. The solution was placed in a microwave oven under a nitrogen atmosphere and microwaved at a power of 700 W and a heating rate of 170 °C / min for 5 min. Afterward, the solution was cooled to room temperature with the oven, and solid-liquid separation was performed. The separated solid product was washed three times with hot water, filtered, and dried to obtain carbon-coated iron pyrophosphate sodium.

[0038] The obtained positive electrode material was subjected to half-cell charge-discharge testing. The method was as follows: CR2032 button cells were assembled in an argon-filled glove box with sodium metal sheets as the negative electrode, and glass fiber membrane (GF / AWhat-man) was used as the separator. The electrolyte was a mixture of NP-009 (1M NaPF6 in (PC) with 5% (FEC)) with a slurry ratio of NFPP:SP:PVDF = 8:1:1. The mixture was coated on carbon-coated aluminum foil and dried at 60°C for ten hours. The active material loading was approximately 3.52 mg / cm³. -2 Test: After resting for 4 hours, the voltage range of the multiplier (0.1C) is 2.0V-4.0V.

[0039] Figure 4-6 The images show the SEM, XRD, and electrical properties of the composite material prepared in Example 2.

[0040] The figure shows that the material synthesized by the microwave method has uniform and small primary particles in the 50-100 nm range, with good dispersibility, which is beneficial to the material's performance. XRD shows characteristic peaks consistent with the standard card for sodium iron pyrophosphate. The charging capacity is 112 mAh / g and the discharging capacity is 103 mAh / g at 0.1C (1C = 129 mAh).

[0041] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A method for synthesizing carbon-coated iron pyrophosphate sodium based on microwave method, characterized in that, Includes the following steps: 1) Dissolve the iron source, phosphorus source, sodium source and complexing agent in water to prepare a mixed aqueous solution; wherein the complexing agent is selected from sodium triacetate, ethylenediaminetetraacetic acid, diethylenetriaminepentacarboxylic acid, glucose, sucrose, oxalic acid, citric acid and tartaric acid; 2) The mixed aqueous solution prepared in step 1) is subjected to microwave treatment under an inert atmosphere, wherein the heating rate of microwave treatment is 100-300℃ / min and the microwave treatment time is 1-6min. 3) After the reaction is complete, post-processing yields carbon-coated iron pyrophosphate sodium.

2. The method according to claim 1, characterized in that, In step 1), the molar ratio of Fe element to complexing agent in the iron source is 1:1~2.

3. The method according to claim 1, characterized in that, In step 1), iron from the iron source, phosphorus from the phosphorus source, and sodium from the sodium source are added in the stoichiometric ratio of Na4Fe3(PO4)2P2O7.

4. The method according to claim 1, characterized in that, In step 1), the concentration of Fe element in the iron source in the mixed aqueous solution is 0.8-1.2 mol / L.

5. The method according to claim 1, characterized in that, In step 1), the iron source is selected from ferrous sulfate, ferric chloride, ferrous acetate, ferric nitrate, ferric bromide, ferric iodide, and ferric fluoride; the phosphorus source is selected from phosphoric acid; and the sodium source is selected from sodium carbonate, sodium dihydrogen phosphate, and sodium oxalate.

6. The method according to claim 1, characterized in that, In step 2), the power of microwave processing is 600-800W.

7. The method according to claim 1, characterized in that, In step 2), the microwave treatment time is 3-5 minutes.

8. The method according to claim 1, characterized in that, In step 2), the inert atmosphere protection is nitrogen protection.

9. The method according to claim 1, characterized in that, In step 3), the post-processing is as follows: after the reaction is completed, the mixture is cooled, and then solid-liquid separation is performed. The separated solid product is then washed and dried.

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