Preparation method and application of highly stable sodium iron pyrophosphate material

Abstract

The present invention discloses a method for preparing a highly stable sodium ferric pyrophosphate material. The chemical formula of the highly stable sodium ferric pyrophosphate material is Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5‑x (PO4)2(P2O7) / C composite material, wherein x is 0.1-0.5; the Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5‑x The (PO4)2(P2O7) / C composite material is prepared via a sol-gel method. This simple synthesis process involves low-cost, clean, and pollution-free elements. The resulting material exhibits high specific capacity between 1.5 and 4.2V in sodium-ion batteries and exhibits a high Na+ diffusion coefficient, making it suitable for industrial production and promotion. The invention also discloses the use of a highly stable sodium iron pyrophosphate material in sodium-ion batteries.

Description

Technical Field

[0001] The invention relates to a preparation method and application of a highly stable sodium ferric pyrophosphate material. Background Art

[0002] In recent years, with the development of electric vehicles, the demand for lithium batteries has surged. Unfortunately, lithium (Li) is extremely rare (20 ppm) and unevenly distributed on Earth. Sodium (Na) shares similar physical and chemical properties with lithium (Li) and is the fifth most abundant element in the Earth's crust. These properties make sodium-ion batteries (SIBs) an ideal alternative to lithium-ion batteries, especially in large-scale energy storage systems (ESSs), such as smart grids and electric vehicles. However, many technical challenges remain to be overcome in the field of Na-ion batteries, particularly the development of low-cost, high-performance cathode materials. Sodium ferric pyrophosphate (NFPP), Na₄Fe₃(PO₄)₂(P₂Oₐ) (NFPP), has emerged as an ideal cathode material for Na-ion batteries due to its low cost, environmental friendliness, excellent structural stability, and long cycle life. However, its low intrinsic electronic conductivity and the presence of impurities (NaFP and NFPP) hinder its practical application. Doping with different metal elements not only improves its electronic conductivity and sodium ion diffusion coefficient, but also effectively inhibits the formation of sodium iron phosphate and sodium iron pyrophosphate hybrid phases during the synthesis process, effectively ensuring the NASCION structure of sodium iron phosphate pyrophosphate. Furthermore, doping with different metal elements can also reduce the migration barrier of Na ions and improve the sodium ion diffusion coefficient. Therefore, the development of new and efficient doped sodium iron phosphate pyrophosphate cathode materials is of practical significance. Summary of the Invention

[0003] The purpose of the present invention is to overcome the defects of the prior art and provide a method for preparing a highly stable sodium iron pyrophosphate material. The synthesis process is simple, the cost of the elements involved is low, and the material is clean and pollution-free. The obtained material is applied to sodium ion batteries and exhibits a high specific capacity between 1.5 and 4.2V, and has a high Na+ diffusion coefficient, which is suitable for industrial production and promotion.

[0004] Another object of the present invention is to provide a highly stable sodium iron pyrophosphate material for use as a positive electrode in a sodium ion battery.

[0005] A technical solution to achieve the above purpose is: a method for preparing a highly stable sodium iron pyrophosphate material, wherein the chemical formula of the highly stable sodium iron pyrophosphate material is Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5-x(PO4)2(P2O7) / C composite material, wherein x is 0.1-0.5; the Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5-x The (PO4)2(P2O7) / C composite material is prepared by a sol-gel method, specifically, sodium source material, iron source material, phosphorus source material, manganese acetate, copper acetate, magnesium acetate, nickel acetate, zinc acetate, phosphoric acid and citric acid are dissolved in deionized water, then heated in an oil bath to 100-120°C, reacted for 8-12 hours to form a gel-like substance, then the gel-like substance is transferred to a drying oven, dried at 200-250°C, and then ground; the powdered product obtained by grinding is sintered in a tubular atmosphere furnace, and the sintered product is cooled and crushed to obtain Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5-x (PO4)2(P2O7) / C composite material.

[0006] The above-mentioned method for preparing a highly stable sodium iron pyrophosphate material, wherein the molar ratio of Na:Fe:P in the sodium source material, iron source material and phosphorus source material is 1:(2.5+x):4, ​​wherein x is 0.1-0.5.

[0007] The above-mentioned method for preparing a highly stable sodium ferric pyrophosphate material, wherein the sodium source material is one or more of sodium carbonate, sodium hydroxide, sodium sulfate and sodium dihydrogen phosphate;

[0008] The iron source material is one or more of ferric acetate monohydrate, ferric nitrate nonahydrate, ferrous oxalate monohydrate, ferric oxide and ferric phosphate dihydrate;

[0009] The phosphorus source material is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphorus pentoxide.

[0010] The above-mentioned method for preparing a highly stable sodium iron pyrophosphate material, wherein the manganese acetate, copper acetate, magnesium acetate, nickel acetate and zinc acetate are salts corresponding to the respective doping elements, and are all soluble salts.

[0011] The above-mentioned method for preparing a highly stable sodium iron pyrophosphate material, wherein the molar ratio of Mn:Cu:Mg:Ni:Zn in the manganese acetate, copper acetate, magnesium acetate, nickel acetate and zinc acetate is 3:3:2:1:1.

[0012] The above-mentioned method for preparing a highly stable sodium iron pyrophosphate material, wherein the sintering conditions are first keeping warm at 300-350°C for 3-7 hours, then keeping warm at 500-600°C for 10-15 hours, and the heating rate during the sintering process is 2-5°C / min.

[0013] The present invention also provides an application of a highly stable sodium iron pyrophosphate material in a sodium ion battery.

[0014] The above-mentioned high-stable sodium iron pyrophosphate material is used, wherein the high-stable sodium iron pyrophosphate material is used as a positive electrode material.

[0015] The preparation method and application technical solution of the highly stable sodium iron pyrophosphate material of the present invention have a simple synthesis process, low cost of the elements involved, and are clean and pollution-free. The obtained material is applied to sodium ion batteries and exhibits a high specific capacity between 1.5 and 4.2 V, and has a high Na+ diffusion coefficient, which is suitable for industrial production and promotion. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Na4Fe of Example 1 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 The first charge and discharge curves of (PO4)2(P2O7) / C composite material at 0.1C rate when used as the positive electrode of sodium ion battery;

[0017] Figure 2 Na4Fe of Example 1 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 GITT curve at 0.1C rate when (PO4)2(P2O7) / C composite material is used as the positive electrode of sodium ion battery;

[0018] Figure 3 Na4Fe of Example 2 2.6 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.31 The first charge and discharge curve at 0.1C rate when (PO4)2(P2O7) / C composite material is used as the positive electrode of sodium ion battery;

[0019] Figure 4 Na4Fe of Comparative Example 1 2.91 The first charge and discharge curves of (PO4)2P2O7 / C composite material at 0.1C rate when used as the positive electrode of sodium ion battery;

[0020] Figure 5 Na4Fe of Comparative Example 1 2.91 GITT curve at 0.1C rate when (PO4)2P2O7 / C composite material is used as the positive electrode of sodium ion battery;

[0021] Figure 6 Na4Fe of Comparative Example 1 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 The first charge and discharge curve at a rate of 0.1C when the (PO4)2(P2O7) / C (the doped element raw material is a metal oxide) composite material is used as the positive electrode of a sodium ion battery. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the technical solution of the present invention, the specific implementation methods thereof are described in detail below with reference to the accompanying drawings:

[0023] Example 1

[0024] See also Figure 1 and Figure 2 , a highly stable sodium iron pyrophosphate material, the chemical formula is Na4Fe 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 The (PO4)2(P2O7) / C composite material was prepared by the sol-gel method, specifically:

[0025] Add 12.61g of citric acid, 9.05g of ferrous acetate monohydrate, 0.6g of manganese acetate, 0.49g of copper acetate, 0.35g of magnesium acetate, 0.2g of nickel acetate, 0.15g of zinc acetate and 12.48g of sodium dihydrogen phosphate to 200mL of deionized water, stir for 1 hour to completely dissolve it, then transfer it to an oil bath and heat and stir at 120°C for 10 hours to form a gel-like substance, then transfer the gel-like substance to a blast drying oven and dry it at 200°C for 10 hours and grind it. The light yellow powder obtained by grinding is placed in a tubular gas furnace for sintering, and is kept at 300°C for 5 hours and 570°C for 10 hours in sequence. The heating rate during the sintering process is 2-5°C / min; the sintered powder is cooled and ground to finally obtain Na4Fe 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 (PO4)2(P2O7) / C composite material.

[0026] In the voltage range of 1.5~4.2V, the Na4Fe 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 The sodium ion battery with (PO4)2(P2O7) / C composite material as the positive electrode was subjected to charge and discharge tests and GITT tests. Figure 1 The charge and discharge characteristic curve at 0.1C rate shows that the material has a charge and discharge capacity of 112.4 mAh g at 0.1C. -1 reversible discharge capacity. Figure 2 Na4Fe 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 The GITT test curve of (PO4)2(P2O7) / C shows that its Na ion diffusion coefficient is 10 -8 ~10 -10 cm 2 s -1 between.

[0027] Example 2

[0028] See also Figure 3 , a highly stable sodium iron pyrophosphate material, the chemical formula is Na4Fe 2.6(Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.31 The (PO4)2(P2O7) / C composite material was prepared by the sol-gel method, specifically:

[0029] Add 12.61g of citric acid, 9.4g of ferrous acetate monohydrate, 0.46g of manganese acetate, 0.37g of copper acetate, 0.26g of magnesium acetate, 0.15g of nickel acetate, 0.11g of zinc acetate and 12.48g of sodium dihydrogen phosphate to 200mL of deionized water, stir for 1 hour to completely dissolve it, then transfer it to an oil bath and heat and stir at 120°C for 10 hours to form a gel-like substance, then transfer the gel-like substance to a blast drying oven and dry it at 200°C for 10 hours and grind it. The obtained light yellow powder is placed in a tubular gas furnace for sintering, and is kept at 300°C for 5 hours and 570°C for 10 hours in sequence. The heating rate during the sintering process is 2-5°C / min; the sintered powder is cooled and ground to finally obtain Na4Fe 2.6 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.31 (PO4)2(P2O7) / C composite material.

[0030] In the voltage range of 1.5~4.2V, the Na4Fe 2.6 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.31 Charge and discharge tests were carried out on sodium ion batteries with (PO4)2(P2O7) / C composite material as the positive electrode. Figure 3 The charge and discharge characteristic curve at 0.1C rate shows that the material has a charge and discharge capacity of 109.8 mAh g at 0.1C. -1 reversible discharge capacity.

[0031] Comparative Example 1

[0032] See also Figure 4 and Figure 5 , Na4Fe 2.91 The (PO4)2P2O7 / C composite material is prepared by the sol-gel method, specifically:

[0033] Add 12.61g of citric acid, 10.53g of ferrous acetate monohydrate and 12.48g of sodium dihydrogen phosphate to 200mL of deionized water, stir for 1 hour to completely dissolve, then transfer to an oil bath and heat and stir at 120°C for 10 hours to form a gel-like substance, then transfer the gel-like substance to a blast drying oven and dry at 200°C for 10 hours and grind. The obtained powder is placed in a tubular gas furnace for sintering, and kept at 300°C for 5 hours and 570°C for 10 hours, respectively. The heating rate during the sintering process is 2-5°C / min; the sintered powder is cooled and ground to finally obtain Na4Fe 2.91 (PO4)2P2O7 / C composite material.

[0034] In the voltage range of 1.5~4.2V, the Na4Fe 2.91 Sodium ion batteries with (PO4)2P2O7 / C composite material as positive electrode were subjected to charge and discharge tests and constant current intermittent titration (GITT) tests. Figure 4 The charge and discharge characteristic curve at 0.1C rate shows that the material has a charge and discharge capacity of 100.3 mAh g at 0.1C. -1 reversible discharge capacity. Figure 5 Na4Fe 2.91 The GITT test curve of (PO4)2P2O7 / C shows that its Na ion diffusion coefficient is 10 -9 ~10 -11 cm 2 s -1 between.

[0035] Comparative Example 2

[0036] See also Figure 6 According to the experimental steps described in Example 2, the soluble salts corresponding to the doping elements were replaced with the corresponding metal oxides, that is, manganese acetate, copper acetate, magnesium acetate, nickel acetate and zinc acetate were replaced with the corresponding metal oxides, and the molar ratio did not change, to obtain the material Na4Fe 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 (PO4)2(P2O7) / C (the raw material of the doping element is a metal oxide), a sodium ion battery with the material prepared in Comparative Example 2 as the positive electrode was charged and discharged in the voltage range of 1.5 to 4.2 V at a rate of 0.1C. Figure 6 The charge-discharge characteristic curve at 0.1C rate shows that the material of Comparative Example 2 has a charge-discharge capacity of 91.8 mAh g at 0.1C. -1reversible discharge capacity.

[0037] The specific capacities and sodium ion diffusion coefficients of the materials of Example 1, Example 2, Comparative Example 1 and Comparative Example 2 are summarized in Table 1.

[0038] Table 1, performance parameters of materials of Example 1, Example 2, Comparative Example 1 and Comparative Example 2:

[0039]

[0040] According to the sodium ion diffusion coefficients of Example 1 and Comparative Example 1 in Table 1, it can be seen that the Na ion diffusion coefficient of the material of Example 1 is 10 -8 ~10 -10 cm 2 s -1 The Na ion diffusion coefficient of the material of Comparative Example 1 is between 10 -9 ~10 -11 cm 2 s -1 Between, the Na4Fe of Example 1 2.5 (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.41 The sodium ion diffusion coefficient of the (PO4)2(P2O7) / C composite material is reduced by an order of magnitude, indicating that the doping of different metal ions can indeed reduce the migration barrier of Na ions and increase the sodium ion diffusion coefficient. The doping elements effectively improve the problem of low inherent electronic conductivity of NFPP materials.

[0041] According to the specific capacities of Example 2 and Comparative Example 2 in Table 1, the material of Example 2 has a specific capacity of 109.8 mAh g at 0.1 C. -1 The reversible discharge capacity of the material in Comparative Example 2 is 91.8 mAh g at 0.1C. -1 The reversible discharge specific capacity is achieved by introducing doping elements using soluble salts, which is safe and low-cost and can exhibit a higher specific capacity.

[0042] The present invention relates to a method for preparing a highly stable sodium ferric pyrophosphate material. The sodium source material can be one or more sodium-containing compounds such as sodium carbonate, sodium hydroxide, sodium sulfate, and sodium dihydrogen phosphate; the iron source material can be one or more Fe-containing compounds such as ferric acetate monohydrate, ferric nitrate nonahydrate, ferrous oxalate monohydrate, ferric oxide, and ferric phosphate dihydrate; and the phosphorus source material can be one or more P-containing compounds such as phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, and phosphorus pentoxide. Manganese acetate, copper acetate, magnesium acetate, nickel acetate, and zinc acetate are soluble salts corresponding to the respective doping elements. High-entropy doping effectively improves the inherent low electronic conductivity of NFPP materials; the high-entropy doped elements are all safe and low-cost elements; and high-entropy doping can effectively improve the structural stability of NFPP.

[0043] In summary, the preparation method and application of the highly stable sodium iron pyrophosphate material of the present invention have simple synthesis process, low cost and clean and pollution-free element species involved, and the obtained material is applied to sodium ion batteries and exhibits high specific capacity between 1.5 and 4.2 V, and has high Na + Diffusion coefficient, suitable for industrial production and promotion.

[0044] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. A method for preparing a highly stable sodium iron pyrophosphate material, characterized in that: The chemical formula of the highly stable sodium iron pyrophosphate material is Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5-x (PO4)2(P2O7) / C composite material, wherein x is 0.1-0.5; the Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5-x The (PO4)2(P2O7) / C composite material is prepared by a sol-gel method, specifically, sodium source material, iron source material, phosphorus source material, manganese acetate, copper acetate, magnesium acetate, nickel acetate, zinc acetate, phosphoric acid and citric acid are dissolved in deionized water, then heated in an oil bath to 100-120°C, reacted for 8-12 hours to form a gel-like substance, then the gel-like substance is transferred to a drying oven, dried at 200-250°C, and then ground; the powdered product obtained by grinding is sintered in a tubular atmosphere furnace, and the sintered product is cooled and crushed to obtain Na4Fe 2.5+x (Mn 0.3 Cu 0.3 Mg 0.2 Ni 0.1 Zn 0.1 ) 0.5-x (PO4)2(P2O7) / C composites; In the sodium source material, the iron source material and the phosphorus source material, the molar ratio of Na:Fe:P is 1:(2.5+x):4, ​​wherein x is 0.1-0.5; Among the manganese acetate, copper acetate, magnesium acetate, nickel acetate and zinc acetate, the molar ratio of Mn:Cu:Mg:Ni:Zn is 3:3:2:1:1; The sintering conditions are: first keeping the temperature at 300-350° C. for 3-7 hours, then keeping the temperature at 500-600° C. for 10-15 hours, and the heating rate during the sintering process is 2-5° C. / min.

2. The method for preparing a highly stable sodium iron pyrophosphate material according to claim 1, wherein: The sodium source material is one or more of sodium carbonate, sodium hydroxide, sodium sulfate and sodium dihydrogen phosphate; The iron source material is one or more of ferric acetate monohydrate, ferric nitrate nonahydrate, ferrous oxalate monohydrate, ferric oxide and ferric phosphate dihydrate; The phosphorus source material is one or more of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate and phosphorus pentoxide.

3. The method for preparing a highly stable sodium iron pyrophosphate material according to claim 1, wherein: The manganese acetate, copper acetate, magnesium acetate, nickel acetate and zinc acetate are salts corresponding to the doping elements, and are all soluble salts.

4. Use of the highly stable sodium iron pyrophosphate material according to claim 1 in a sodium ion battery.

5. The use of a highly stable sodium iron pyrophosphate material according to claim 4, characterized in that: The highly stable sodium iron pyrophosphate material is used as a positive electrode material.

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