Preparation method of high-performance sodium ferric phosphate positive electrode material

Abstract

The invention relates to a preparation method of a high-performance sodium ferric phosphate positive electrode material, and belongs to the technical field of preparation of electrochemical energy storage and secondary battery electrode materials. The preparation method comprises the following steps: chelating a manganese source, an iron source and a vanadium source with a chelating agent, mixing with a phosphorus source solution and a sodium source solution, and sintering to obtain an active material; and grinding and uniformly mixing the prepared active material, carbon black and a polytetrafluoroethylene binder, and coating an aluminum foil with the mixture. According to the invention, the efficient chelating synergist is prepared from the vinyl guanamine, the gadoleic acid quinoline ester, the 2, 4, 6-triallyloxy-1, 3, 5-triazine and the benzoyl peroxide, so that the electrochemical performance, including high-rate discharge performance and cycle stability, of the sodium iron phosphate positive electrode material is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of electrochemical energy storage and the preparation of secondary battery electrode materials, and specifically relates to a method for preparing a high-performance sodium iron phosphate electrode material. Background Art

[0002] Sodium-ion batteries are regarded as a potential energy storage technology due to their advantages such as rich raw materials, low cost, and environmental friendliness.

[0003] Currently, the positive electrode materials of sodium-ion batteries are mainly divided into three categories, namely layered oxides, Prussian blue, and polyanion-type materials. Among these materials, polyanion-type sodium-ion battery positive electrode materials have attracted much attention due to their unique advantages. Polyanion-type compounds are compounds with a three-dimensional network structure formed by connecting polyanion polyhedra and various metal ion polyhedra through strong covalent bonds. Sodium ions occupy the channel positions therein, and their structure can support a stable crystal framework structure, improve cyclicity and safety, and at the same time have the advantages of high specific capacity and good air stability.

[0004] CN116789097A relates to the technical field of sodium iron phosphate preparation, and provides a method for preparing sodium iron phosphate. After reacting a ternary precursor reaction mother liquor with a sodium sulfite solution and iron phosphate, solid-liquid separation, drying, and mixing with glucose for sintering are carried out: The ternary precursor reaction mother liquor, the sodium sulfite solution, and iron phosphate are introduced into a reaction kettle, the molar ratio of sodium sulfite to iron phosphate is controlled to be 0.4 - 1.1, the pH is controlled to be 4 - 7 using sodium hydroxide and sulfuric acid, the reaction temperature is controlled to be 40 - 100 °C, and a sodium iron phosphate feed liquid is obtained through reaction; the feed liquid is subjected to solid-liquid separation, and then dried. The dried material is sintered with glucose at 700 - 900 °C to obtain a sodium iron phosphate positive electrode material.

[0005] CN116750742A relates to a method for preparing a sodium iron phosphate material and the sodium iron phosphate material. The method includes: 1) Dissolving a divalent / trivalent iron source in deionized water to form solution A. 2) Dissolving an alkaline substance in deionized water to prepare solution B, dropping solution B into solution A, stirring until the pH of the solution is 4 - 8, and centrifuging and filtering the obtained slurry. 3) Dissolving a chloride and / or fluoride and phosphate in deionized water to prepare solution C, dispersing the slurry obtained in step 2) in solution C, stirring for 0.5 - 24 h, filtering, and drying to obtain the target product. The present invention proposes a new method for efficiently preparing nano sodium iron phosphate by using a two-step particle size control method under low-temperature conditions.

[0006] CN116730314A discloses a method for modifying a sodium iron phosphate cathode material, comprising the following steps: S1. Add sodium iron phosphate, a dopant, and EDOT to deionized water, stir evenly to obtain a mixed solution A; S2. Slowly add a dispersant to the mixed solution A, then dropwise add an aqueous solution of an oxidant under stirring, stir and react after dropping, perform solid-liquid separation after the reaction, and wash and dry the obtained solid substance to obtain the product.

[0007] The polyanion cathode materials prepared by the current existing technologies generally have poor conductivity, and the specific capacity of the M-phase sodium iron phosphate material obtained by the conventional calcination process is only 70-90 mAh / g, which greatly affects its electrochemical performance and still cannot meet the electrochemical application requirements under high load, making it difficult to achieve large-scale application. Summary of the Invention

[0008] In order to achieve the above object, the present invention provides the following technical solutions:

[0009] A method for preparing a high-performance sodium iron phosphate cathode material, comprising the following steps:

[0010] Step 1: Dissolve 8-36 parts by mass of a manganese source, 7-36 parts by mass of an iron source, 9-36 parts by mass of a vanadium source, 0.5-11 parts of a chelating agent, and 0.05-2 parts of a high-efficiency chelating synergist in 120-200 parts of deionized water, and stir and dissolve at 60-110 °C to prepare a solution A;

[0011] Step 2: Dissolve 10-63 parts by mass of a phosphorus source, 16-100 parts by mass of a sodium source, and 2-16 parts of a reducing agent in 200-300 parts of deionized water, and stir and dissolve at a constant temperature of 60-110 °C to form a solution B;

[0012] Step 3: Keep the mixed solution of solution A and solution B stirring at a constant temperature of 80-130 °C until the solvent evaporates to obtain a gel precursor material, transfer the precursor material to a high-temperature sintering at 300-500 °C for 6-24 h under an inert atmosphere, and cool to room temperature to obtain a semi-finished product;

[0013] Step 4: Sinter the semi-finished product at 450-750 °C for 4-24 h in an inert atmosphere, cool and pulverize to obtain an active material; uniformly grind and mix the obtained active material, carbon black, and polytetrafluoroethylene binder in a mass ratio of 90:5:5, coat it on an aluminum foil, and fully roll it with a roll mill to form a film with a uniform thickness, and dry it in a vacuum drying oven at 120 °C for 5 hours to obtain the cathode material.

[0014] Further, the manganese source in step 1 is one or more of manganese acetate, manganese oxalate, manganese carbonate, manganese nitrate, manganese monoxide, manganese dioxide, and manganese phosphate.

[0015] Further, the iron source described in step one is at least one of iron(III) oxide, iron(III) nitrate, iron(III) phosphate, iron(III) chloride, iron(II) chloride, iron(III) citrate, and iron(II) oxalate.

[0016] Further, the vanadium source described in step one is at least one of vanadium(V) oxide, vanadium(III) oxide, sodium metavanadate, or ammonium metavanadate.

[0017] Further, the chelating agent described in step one is at least one of ethylenediaminetetraacetic acid, citric acid, tartaric acid, diethylenetriaminepentaacetic acid, ethylenediamine, sulfosalicylic acid, ascorbic acid, and oxalic acid.

[0018] Further, the phosphorus source described in step two is at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium hydrogen phosphate, or sodium dihydrogen phosphate.

[0019] Further, the sodium source described in step two is at least one of sodium carbonate, sodium bicarbonate, sodium phosphate, sodium dihydrogen phosphate, sodium citrate, sodium alginate, sodium hydroxide, sodium acetate, or sodium oxalate.

[0020] Further, the reducing agent described in step two is at least one of glucose, sucrose, starch, and polyethylene glycol.

[0021] Further, the inert atmosphere described in steps three and four is at least one of nitrogen, argon, helium, or a hydrogen-argon mixture.

[0022] Further, the preparation method of the high-efficiency chelating synergist described in step one is as follows:

[0023] By weight, take 200 - 300 parts of toluene, 12 - 24 parts of vinylguanamine, 0.03 - 0.3 parts of quinoline acrylate, CAS: 34462 - 96 - 9, 0.05 - 0.5 parts of 2,4,6 - triallyloxy - 1,3,5 - triazine, and 2 - 5 parts of benzoyl peroxide. Then place them in a water bath at 60°C - 80°C and stir the above solution for 2 - 4 h. Distill off the toluene to obtain the high - efficiency chelating agent.

[0024] Reaction mechanism

[0025] 1. Vinylguanamine has strong addition reactivity and can undergo an addition reaction with water in an acidic aqueous solution to form a salt that is soluble in water. It can copolymerize with other monomers through a free - radical polymerization reaction to increase the softening point temperature and glass transition temperature of the polymer material. Quinoline acrylate can act as a ligand to form complexes with metal ions, and coordinate with metal ions using the carbonyl and nitrogen atoms in its molecule. This coordination enhances the chelating ability of the material. The amino group on the triazine ring can adsorb water - soluble molecules through hydrogen - bonding, enhancing the adsorption ability and stability of the material. The introduction of the triazine group improves the mechanical properties and thermal stability of the polymer.

[0026] 2. Vinyl guanamine, quinoline acrylate and 2,4,6-triallyloxy-1,3,5-triazine are copolymerized by free radical polymerization in the presence of a suitable initiator (such as a cationic radical initiator). During the reaction process, the monomer feeding rate and the ratio of monomer to initiator are controlled to obtain good particle morphology and narrow size distribution.

[0027] Technical effects

[0028] 1. Enhance electrochemical performance: The introduced guanamine and quinoline ester groups enhance the chelation of the material, improving the electrochemical performance of the sodium iron phosphate cathode material, including high-rate discharge performance and cycle stability.

[0029] 2. Improve structural stability: The introduction of the triazine group helps to maintain the structural integrity of the electrode material, reducing volume changes and particle fragmentation during cycling.

[0030] 3. Enhance adsorption capacity: The amino groups on the triazine ring enhance the adsorption capacity of the material through hydrogen bonding, contributing to improving the charge-discharge efficiency and capacity retention rate of the battery.

[0031] 4. Optimize conductivity: The structure and composition of the copolymer optimize the electron and ion transport paths, enhancing the conductivity and ion conductivity of the electrode material and further improving the overall performance of the battery.

[0032] In summary, the high-efficiency chelating synergist generated by the ternary copolymerization of vinyl guanamine, quinoline acrylate and 2,4,6-triallyloxy-1,3,5-triazine significantly improves the electrochemical performance of the sodium iron phosphate cathode material through its special molecular structure and functional groups. Specific embodiments

[0033] The technical solution of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations to the present invention.

[0034] Example 1

[0035] A preparation method of a high-performance sodium iron phosphate cathode material includes the following steps:

[0036] Step 1: According to mass parts, 8 g of manganese source, 7 g of iron source, 9 g of vanadium source, 0.5 g of chelating agent and 0.05 g of high-efficiency chelating synergist are dissolved in 120 g of deionized water, and stirred and dissolved at 60 °C to prepare solution A;

[0037] Step 2: 10 g of phosphorus source, 16 g of sodium source and 2 g of reducing agent are dissolved in 200 g of deionized water, and stirred and dissolved at a constant temperature of 60 °C to form solution B;

[0038] Step 3: Keep the mixture of Solution A and Solution B under constant stirring at 80 °C until the solvent evaporates to obtain a gel precursor material. Transfer the precursor material to a high-temperature sintering process at 300 °C for 6 h under an inert atmosphere, and then cool it to room temperature to obtain a semi-finished product.

[0039] Step 4: Sinter the semi-finished product at 450 °C for 4 h in an inert atmosphere, cool it, and crush it to obtain an active material. Mix the obtained active material, carbon black, and polytetrafluoroethylene binder evenly by grinding according to a mass ratio of 90:5:5, coat it on an aluminum foil, and roll it with a roller machine to form a film with a uniform thickness. Dry it in a vacuum drying oven at 120 °C for 5 hours to obtain a positive electrode material.

[0040] The manganese source described in Step 1 is manganese monoxide.

[0041] The iron source described in Step 1 is ferrous chloride.

[0042] The vanadium source described in Step 1 is ammonium metavanadate.

[0043] The chelating agent described in Step 1 is ethylenediaminetetraacetic acid.

[0044] The phosphorus source described in Step 2 is phosphoric acid.

[0045] The sodium source described in Step 2 is sodium hydroxide.

[0046] The reducing agent described in Step 2 is polyethylene glycol.

[0047] The inert atmosphere described in Step 3 and Step 4 is nitrogen.

[0048] The preparation method of the high-efficiency chelating synergist described in Step 1 is as follows:

[0049] By weight, add 200 g of toluene, 12 g of vinylguanamine, 0.03 g of quinoline acrylate, 0.05 g of 2,4,6-triallyloxy-1,3,5-triazine, and 2 g of benzoyl peroxide. Then place it in a water bath at 60 °C and stir the above solution for 2 h. Distill off the toluene to obtain a high-efficiency chelating agent.

[0050] Example 2

[0051] A preparation method of a high-performance sodium iron phosphate positive electrode material, comprising the following steps:

[0052] Step 1: Dissolve 22 g of manganese source, 23 g of iron source, 21 g of vanadium source, 6 g of chelating agent, and 1 g of high-efficiency chelating synergist in 160 g of deionized water according to mass parts, and stir and dissolve at 90 °C to prepare Solution A;

[0053] Step 2: Dissolve 35 g of phosphorus source, 55 g of sodium source and 9 g of reducing agent in 250 g of deionized water, and stir and dissolve at a constant temperature of 85 °C to form solution B;

[0054] Step 3: Keep the mixed solution of solution A and solution B stirring at a constant temperature of 105 °C until the solvent evaporates to obtain a gel precursor material, and transfer the precursor material to a high-temperature sintering at 400 °C for 15 h under an inert atmosphere, and cool to room temperature to obtain a semi-finished product;

[0055] Step 4: Sinter the semi-finished product at 600 °C for 14 h in an inert atmosphere, cool and crush to obtain an active material; after uniformly grinding and mixing the prepared active material, carbon black, and polytetrafluoroethylene binder according to a mass ratio of 90:5:5, coat it on an aluminum foil, and use a pair-roller machine to fully roll and press to form a film with a uniform thickness, and dry it in a vacuum drying oven at 120 °C for 5 hours to obtain a positive electrode material.

[0056] The manganese source described in Step 1 is manganese acetate and manganese oxalate.

[0057] The iron source described in Step 1 is iron(III) oxide.

[0058] The vanadium source described in Step 1 is vanadium(III) oxide.

[0059] The chelating agent described in Step 1 is ethylenediamine.

[0060] The phosphorus source described in Step 2 is sodium dihydrogen phosphate.

[0061] The sodium source described in Step 2 is sodium acetate.

[0062] The reducing agent described in Step 2 is glucose.

[0063] The inert atmosphere described in Step 3 and Step 4 is a hydrogen-argon mixture.

[0064] The preparation method of the high-efficiency chelating synergist described in Step 1 is as follows:

[0065] By weight, add 250 g of toluene, 18 g of vinyl guanamine, 0.15 g of quinoline acrylate, 0.3 g of 2,4,6-triallyloxy-1,3,5-triazine, 3.5 g of benzoyl peroxide, and then place it in a 70 °C water bath, stir the above solution for 3 h, distill off toluene, and obtain a high-efficiency chelating agent.

[0066] Example 3

[0067] A preparation method of a high-performance sodium iron phosphate positive electrode material, comprising the following steps:

[0068] Step 1: According to the mass parts, dissolve 36 g of manganese source, 36 g of iron source, 36 g of vanadium source, 11 g of chelating agent and 2 g of high-efficiency chelating synergist in 200 g of deionized water, and stir and dissolve at 110 °C to prepare solution A;

[0069] Step 2: Dissolve 63 g of phosphorus source, 100 g of sodium source and 16 g of reducing agent in 300 g of deionized water, and stir and dissolve at a constant temperature of 110 °C to form solution B;

[0070] Step 3: Keep the mixed solution of solution A and solution B stirring at a constant temperature of 130 °C until the solvent evaporates to obtain a gel precursor material, and transfer the precursor material to a high-temperature sintering at 500 °C for 24 h under an inert atmosphere, and cool to room temperature to obtain a semi-finished product;

[0071] Step 4: Sinter the semi-finished product at 750 °C for 24 h in an inert atmosphere, cool and crush to obtain an active material; after grinding and mixing the prepared active material, carbon black and polytetrafluoroethylene binder evenly according to the mass ratio of 90:5:5, coat it on the aluminum foil, and use a pair-roll machine to fully roll and press to form a film with a uniform thickness, and dry it in a vacuum drying oven at 120 °C for 5 hours to obtain a positive electrode material.

[0072] The manganese source described in Step 1 is manganese phosphate.

[0073] The iron source described in Step 1 is iron citrate.

[0074] The vanadium source described in Step 1 is vanadium pentoxide.

[0075] The chelating agent described in Step 1 is ascorbic acid.

[0076] The phosphorus source described in Step 2 is sodium hydrogen phosphate.

[0077] The sodium source described in Step 2 is sodium citrate.

[0078] The reducing agent described in Step 2 is sucrose.

[0079] The inert atmosphere described in Step 3 and Step 4 is argon.

[0080] The preparation method of the high-efficiency chelating synergist described in Step 1 is as follows:

[0081] By weight, put 300 g of toluene, 24 g of vinyl guanamine, 0.3 g of quinoline acrylate, 0.5 g of 2,4,6-triallyloxy-1,3,5-triazine, 5 g of benzoyl peroxide, and then place it in a water bath at 60 °C - 80 °C, stir the above solution for 2 - 4 h, distill off toluene, and obtain a high-efficiency chelating agent.

[0082] Comparative Example 1

[0083] In this comparative example, the high-efficiency chelating synergist is not added, and the remaining technical solutions are the same as those in Example 1.

[0084] Comparative Example 2

[0085] In this comparative example, vinyl guanamine is not added to the high-efficiency chelating synergist, and the remaining technical solutions are the same as those in Example 1.

[0086] Comparative Example 3

[0087] In this comparative example, quinoline acrylate is not added to the high-efficiency chelating synergist, and the remaining technical solutions are the same as those in Example 1.

[0088] Comparative Example 4

[0089] In this comparative example, 2,4,6-triallyloxy-1,3,5-triazine is not added to the high-efficiency chelating synergist, and the remaining technical solutions are the same as those in Example 1.

[0090] The preparation method of the sodium-ion battery is as follows: Use a cutting machine to cut the positive electrode material into a circular electrode sheet with a diameter of 12 mm as the positive electrode sheet and a sodium sheet as the negative electrode sheet. Assemble the positive electrode sheet, negative electrode sheet spring piece, gasket, positive electrode shell, negative electrode shell, separator, and electrolyte into a CR2025 type button half-cell in a glove box filled with argon. The electrolyte is an electrolyte formed by dissolving 1 M of NaPF6 in a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) (by volume ratio EC:DMC = 1:1), and the metallic sodium sheet is the counter electrode.

[0091] Under the condition of 25 °C, in the voltage range of 1.5 - 4.0 V, tests are carried out successively at the rates of 0.1C, 0.2C, 0.5C, 1C, 2C, and 0.1C, and the test results are shown in Table 1.

[0092] Table 1

[0093]

[0094]

[0095] According to the data in Table 1, it can be seen that the guanamine, quinoline ester group, and triazine group introduced by adding the high-efficiency chelating agent of the present invention during the preparation process of the positive electrode material enhance the chelating effect of the material and improve the electrochemical performance of the sodium iron phosphate positive electrode material, including high-rate discharge performance and cycle stability.

[0096] The applicant declares that the present invention is further illustrated by the above embodiments, but the present invention is not limited to the above embodiments, that is, it does not mean that the present invention must rely on the above embodiments to be implemented. Those skilled in the art should understand that any improvement to the present invention, the equivalent substitution of each raw material of the present invention's products, the addition of auxiliary components, the selection of specific methods, etc., all fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A preparation method of a high-performance sodium iron phosphate cathode material, comprising the following steps: Step 1: According to mass parts, dissolve 8 - 36 parts of manganese source, 7 - 36 parts of iron source, 9 - 36 parts of vanadium source, 0.5 - 11 parts of chelating agent, and 0.05 - 2 parts of high-efficiency chelating synergist in 120 - 200 parts of deionized water, and stir and dissolve at 60 - 110 °C to prepare solution A; Step 2: Dissolve 10 - 63 parts of phosphorus source, 16 - 100 parts of sodium source, and 2 - 16 parts of reducing agent in 200 - 300 parts of deionized water, and stir and dissolve at a constant temperature of 60 - 110 °C to form solution B; Step 3: Keep the mixed solution of solution A and solution B stirring at a constant temperature of 80 - 130 °C until the solvent evaporates to obtain a gel precursor material, and transfer the precursor material to a high-temperature sintering at 300 - 500 °C for 6 - 24 h under an inert atmosphere, and cool to room temperature to obtain a semi-finished product; Step 4: Sinter the semi-finished product at 450 - 750 °C for 4 - 24 h in an inert atmosphere, cool and crush to obtain an active material; grind and mix the obtained active material, carbon black, and polytetrafluoroethylene binder evenly according to a mass ratio of 90:5:5, coat it on an aluminum foil, and fully roll it with a roller to form a film with a uniform thickness, and dry it in a vacuum drying oven at 120 °C for 5 hours to obtain the cathode material.

2. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The manganese source described in Step 1 is one or more of manganese acetate, manganese oxalate, manganese carbonate, manganese nitrate, manganese monoxide, manganese dioxide, and manganese phosphate.

3. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The iron source described in Step 1 is at least one of ferric oxide, iron nitrate, iron phosphate, ferric chloride, ferrous chloride, iron citrate, and ferrous oxalate.

4. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The vanadium source described in Step 1 is at least one of vanadium pentoxide, vanadium trioxide, sodium dioxovanadate, or ammonium metavanadate.

5. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The chelating agent described in Step 1 is at least one of ethylenediaminetetraacetic acid, citric acid, tartaric acid, diethylenetriaminepentaacetic acid, ethylenediamine, sulfosalicylic acid, ascorbic acid, and oxalic acid.

6. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The phosphorus source described in Step 2 is at least one of phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, sodium hydrogen phosphate, or sodium dihydrogen phosphate.

7. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The sodium source described in Step 2 is at least one of sodium carbonate, sodium bicarbonate, sodium phosphate, sodium dihydrogen phosphate, sodium citrate, sodium alginate, sodium hydroxide, sodium acetate, or sodium oxalate.

8. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The reducing agent described in Step 2 is at least one of glucose, sucrose, starch, and polyethylene glycol.

9. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The inert atmosphere described in Step 3 and Step 4 is at least one of nitrogen, argon, helium, or a hydrogen-argon mixture.

10. The preparation method of a high-performance sodium iron phosphate cathode material according to claim 1, characterized in that: The preparation method of the high-efficiency chelating synergist described in Step 1 is as follows: According to weight parts, take 200 - 300 parts of toluene, 12 - 24 parts of vinylguanamine, 0.03 - 0.3 parts of quinoline acrylate, 0.05 - 0.5 parts of 2,4,6-triallyloxy-1,3,5-triazine, 2 - 5 parts of benzoyl peroxide, and then place it in a water bath at 60 °C - 80 °C, stir the above solution for 2 - 4 h, and distill off toluene to obtain the high-efficiency chelating agent.

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