Synthesis method of composite sodium ferric phosphate material and sodium ion battery thereof
By introducing phosphonic acid groups and carbon-containing phosphorus and carbon sources into composite sodium iron phosphate materials, and doping with transition metals, combined with nano-grinding and pH control methods, the conductivity and voltage problems of composite sodium iron phosphate materials were solved, and high-performance sodium-ion battery materials were synthesized.
Patent Information
- Application Number
- CN202511605843.9
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-05
- Publication Date
- 2026-01-02
AI Technical Summary
Existing composite sodium iron phosphate materials have low intrinsic conductivity and low operating voltage, making it difficult to meet the requirements of high-performance sodium-ion batteries.
A composite sodium iron phosphate material was synthesized by using phosphorus and carbon sources containing phosphonic acid groups and carbon groups, combined with other transition metal doping, through batch feeding, nano-grinding and pH control, forming an amorphous carbon coating, which improves conductivity and voltage.
The working voltage and intrinsic conductivity of the composite sodium iron phosphate material were improved, and the cycle performance was enhanced. The synthesis process is simple and efficient, environmentally friendly with no waste gas or wastewater generated, and the electrode material has high specific capacity and good cycle life.
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Figure CN121247762A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of sodium-ion battery technology, and in particular to a method for synthesizing a composite sodium iron phosphate material and its sodium-ion battery. Background Technology
[0002] With the booming development of the clean energy industry, the demand for large-scale energy storage equipment is increasing. Sodium-ion batteries are widely considered an effective alternative and supplement to lithium-ion batteries due to their abundant raw material resources, low price, and similar working principle. Developing low-cost, high-performance cathode materials is one of the keys to promoting the industrialization of sodium-ion batteries. Composite sodium iron phosphate (NaxFex-1(PO4)x-2P2O7, 3≤x≤4) is considered the best choice for energy storage systems due to its advantages such as low cost, abundant raw materials, and stable long-cycle performance. However, this material still has problems such as low intrinsic conductivity and low operating voltage. These need to be improved by doping with other transition metals and in-situ carbon coating. Therefore, developing a new, environmentally friendly, and low-cost synthesis method for composite sodium iron phosphate cathode materials is of practical significance. Summary of the Invention
[0003] The purpose of this invention is to solve the problems mentioned in the background art by proposing a method for synthesizing composite sodium iron phosphate material and its sodium-ion battery.
[0004] To achieve the above objectives, the present invention adopts the following technical solution: A method for synthesizing a composite sodium iron phosphate material includes the following steps: (1) Weigh out the phosphorus source, the first part of the sodium source and the carbon source, add deionized water and stir. After the raw materials are dissolved or evenly dispersed, continue to add the second part of the sodium source and the iron source, heat to fully react, and then add other transition metal sources to continue the reaction to obtain a precursor solution; grind the precursor solution thoroughly and then dry it to obtain the precursor. (2) The precursor obtained in step (1) is placed under a protective atmosphere and sintered in two stages at high temperature. After natural cooling, the composite sodium iron phosphate material doped with other transition metals is obtained.
[0005] As a further aspect of the present invention: in step (1): The molar ratio of each raw material satisfies: Na:Fe:other transition metals:P=x:x-1-y:y:x, where 3≤x≤4, 0<y≤2.
[0006] As a further aspect of the present invention: in step (1): The phosphorus source is at least one of the following: ammonium dihydrogen phosphate, sodium dihydrogen phosphate, sodium dihydrogen phosphate, sodium phosphate, sodium pyrophosphate, sodium diammonium hydrogen phosphate, phosphoric acid, hydroxyethylidene diphosphonic acid, aminotrimethylene phosphonic acid, ethylenediaminetetramethylene phosphonic acid, or hexamethylenetetramethylene phosphonic acid, and contains at least one organophosphonic acid. The sodium source is at least one of sodium hydroxide, sodium nitrate, sodium carbonate, sodium formate, sodium acetate, sodium ethoxide, sodium gluconate, sodium ascorbate, sodium benzoate, sodium oxalate, sodium malate, or sodium citrate, and contains at least one organic acid sodium.
[0007] As a further aspect of the present invention: in step (1): The carbon source is at least one of glucose, citric acid, sucrose, polyethylene glycol, ascorbic acid, maltose, starch, oxalic acid, malic acid, or polyvinyl alcohol. The iron source is at least one of ferrous phosphate, ferric phosphate, ferrous oxalate, ferric nitrate, iron powder, or iron oxide. The other transition metal source is at least one of sodium metavanadate, vanadium pentoxide, manganese monoxide, manganese dioxide, manganese oxalate, manganese citrate, Marif salt, manganese hydroxide, nickel hydroxide, or cobalt hydroxide.
[0008] As a further aspect of the present invention: the temperature at which the heating reaction is fully completed in step (1) is 50°C to 100°C, and the mass percentage of the carbon source in the precursor is 2% to 15%.
[0009] As a further aspect of the present invention: after adding other transition metal sources in step (1) and continuing the reaction, the pH value of the resulting precursor solution is <7, and the condition for thorough grinding is: using a grinding device to grind the median particle size of the particles in the precursor solution to below 250nm.
[0010] As a further aspect of the present invention: the drying process in step (1) is at least one of spray drying, vacuum drying or flash drying.
[0011] As a further aspect of the present invention: the protective atmosphere in step (2) is at least one of argon, nitrogen or a mixture of hydrogen and argon.
[0012] As a further aspect of the present invention: the first stage is sintered at 250℃~350℃ for 2h~6h, and the second stage is sintered at 550℃~650℃ for 8h~12h.
[0013] A sodium-ion battery using a composite sodium iron phosphate material, comprising the composite sodium iron phosphate material obtained by the above synthesis method.
[0014] Compared with existing technologies, the advantages of this invention are: 1. The selected phosphorus and carbon sources contain phosphonic acid groups and carbon-containing groups, thus possessing multifunctional characteristics. They provide the phosphorus source required for the synthesis of composite sodium iron phosphate and form amorphous carbon for coating. The doping of other transition metals can effectively increase the working voltage of the material and improve its intrinsic conductivity.
[0015] 2. Batch feeding ensures that all raw materials can be dissolved or uniformly dispersed. Nano-grinding can crush larger particles, and the acidic environment with a pH value <7 continuously etches smaller particles in the precursor solution, so that the raw materials are fully mixed at the atomic level. This process, which combines physical grinding and chemical etching, produces materials with fewer impurities, improves cycle performance, and generates no toxic waste gas or wastewater during the entire synthesis process. The synthesis process is simple and efficient, and the resulting electrode material has high specific capacity and good cycle life. Attached Figure Description
[0016] Figure 1 The image shown is the XRD pattern of the sample prepared in Example 1 of this invention.
[0017] Figure 2 This is a SEM image of the sample prepared in Example 1 of the present invention.
[0018] Figure 3 This is a rate performance diagram of the sample prepared in Example 1 of the present invention.
[0019] Figure 4 The above are charge-discharge curves of the sample prepared in Example 1 of this invention at different rates.
[0020] Figure 5 The image shown is the XRD pattern of the sample prepared in Example 2 of this invention.
[0021] Figure 6 This is a SEM image of the sample prepared in Example 2 of the present invention.
[0022] Figure 7 This is a rate performance diagram of the sample prepared in Example 2 of the present invention.
[0023] Figure 8 The above are charge-discharge curves of the sample prepared in Example 2 of this invention at different rates.
[0024] Figure 9 The image shown is the XRD pattern of the sample prepared in Example 3 of this invention.
[0025] Figure 10 This is a SEM image of the sample prepared in Example 3 of the present invention.
[0026] Figure 11 This is a rate performance diagram of the sample prepared in Example 3 of the present invention.
[0027] Figure 12The above are charge-discharge curves of the sample prepared in Example 3 of this invention at different rates. Detailed Implementation
[0028] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. 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 Sodium citrate, nano-ferric phosphate, sodium dihydrogen phosphate, ethylenediaminetetramethylenephosphonic acid, and manganese dioxide were weighed according to the sodium:iron:manganese:phosphorus molar ratio of 3:1.8:0.2:3. Then, 5% of the total mass of citric acid and 5% of polyethylene glycol were weighed.
[0030] The synthesis steps are as follows: Step 1: First, add citric acid, polyethylene glycol, ethylenediaminetetramethylenephosphonic acid, sodium dihydrogen phosphate, and part of sodium citrate to deionized water at twice the total mass of the raw materials, and stir until completely dissolved; then add nano-ferric phosphate and the remaining sodium citrate, and heat and stir the mixed solution at 80°C for 1 hour to complete the first stage reaction; then add manganese dioxide, and continue to heat and stir at 80°C for 1 hour to complete the second stage reaction, obtaining the precursor solution.
[0031] Step 2: The above precursor solution is ground using a nano-milling machine until the median particle size of the particles in the solution is less than 200 nm; the ground solution is then spray-dried to obtain the precursor; the precursor is then placed in a nitrogen protective atmosphere and subjected to two-stage high-temperature sintering: the first stage is held at 350°C for 6 hours, and the second stage is held at 600°C for 10 hours; the product is obtained by natural cooling.
[0032] XRD analysis: Figure 1 The XRD pattern of the product in this embodiment shows that the product is highly consistent with the standard pattern of sodium iron pyrophosphate.
[0033] SEM analysis: Figure 2 The image shown is an SEM image of the product of this embodiment, which shows that the obtained material exhibits a spherical particle morphology.
[0034] Electrochemical performance: The product was assembled into an experimental coin cell for charge-discharge testing, and the results are as follows. Figure 3 and Figure 4 As shown, the material exhibits typical charge-discharge curves of sodium iron pyrophosphate at different rates, demonstrating good rate performance. Its 1C discharge specific capacity is 95.13 mAh g⁻¹. -1After cycling at a high rate of 5-20C, the capacity still reaches 94.65mAhg after cycling at 1C. -1 .
[0035] Example 2 According to the sodium:iron:manganese:phosphorus molar ratio of 3.4:2.3:0.1:3.4, weigh out sodium carbonate, sodium malate, ferrous oxalate, aminotrimethylenephosphonic acid, and Marzaff salt. Then weigh out 2.5% of the total mass of glucose and 6% of the total mass of ascorbic acid.
[0036] The synthesis steps are as follows: Step 1: First, add glucose, ascorbic acid, sodium malate, and aminotrimethylenephosphonic acid to deionized water at twice the total mass of the raw materials and stir until completely dissolved; then add ferrous oxalate and sodium carbonate, and heat and stir the mixed solution at 60°C for 0.5 hours to complete the first stage reaction; then add Marzoff salt and continue to heat and stir at 60°C for 2 hours to complete the second stage reaction and obtain the precursor solution.
[0037] Step 2: Grind the above precursor solution using a nano-grinding mill until the median particle size of the particles in the solution is less than 150 nm; dry the ground solution under vacuum to obtain the precursor; place the precursor in a hydrogen-argon mixed atmosphere for two-stage high-temperature sintering: the first stage is held at 300℃ for 3 hours, and the second stage is held at 600℃ for 6 hours; after sintering, allow it to cool naturally to obtain the product.
[0038] XRD analysis: Figure 5 The XRD pattern of the product obtained in this embodiment shows that the product is highly consistent with sodium iron pyrophosphate.
[0039] SEM analysis: Figure 6 The image shown is an SEM image of the product of this embodiment, which shows that the obtained material exhibits a spherical particle morphology.
[0040] Electrochemical performance: The product was assembled into an experimental coin cell for charge-discharge testing, and the results are as follows. Figure 7 and 8 As shown, the material exhibits typical charge-discharge curves of sodium iron pyrophosphate at different rates, demonstrating good rate performance. Its 1C discharge specific capacity is 86.22 mAh g⁻¹. -1 After cycling at a high rate of 5-20C, the capacity still reaches 83.32 mAh / g after cycling at 1C. -1 .
[0041] Example 3 Weigh out sodium hydroxide, iron oxide, hydroxyethylidene diphosphonic acid, ammonium dihydrogen phosphate, and nickel hydroxide according to the sodium:iron:manganese:phosphorus molar ratio of 4:2.5:0.2:4. Then weigh out 10% of the total mass of citric acid and 5% of the total mass of glucose.
[0042] The synthesis steps are as follows: Step 1: First, add citric acid, glucose, hydroxyethylidene diphosphonic acid, ammonium dihydrogen phosphate, and some sodium hydroxide to three times the total mass of the raw materials in deionized water, and stir until completely dissolved; then add iron oxide and the remaining sodium hydroxide, and heat and stir the mixed solution at 50°C for 0.5 hours to complete the first stage reaction; then add nickel hydroxide, and continue to heat and stir at 50°C for 0.5 hours to complete the second stage reaction, obtaining the precursor solution.
[0043] Step 2: Grind the above precursor solution using a nano-grinding mill until the median particle size of the particles in the solution is less than 200 nm; spray dry the ground solution to obtain the precursor; place the precursor in an argon protective atmosphere and perform two-stage high-temperature sintering: the first stage is held at 280℃ for 2 hours, and the second stage is held at 600℃ for 8 hours; allow it to cool naturally to obtain the product.
[0044] XRD analysis: Figure 9 The XRD pattern of the product obtained in this embodiment shows that the product is highly consistent with sodium iron pyrophosphate.
[0045] SEM analysis: Figure 10 The image shows the SEM image of the product of this embodiment, which reveals that the obtained material exhibits spherical particles.
[0046] Electrochemical performance: The product was assembled into an experimental coin cell for charge-discharge testing, and the results are as follows. Figure 11 and 12 As shown, the material exhibits typical charge-discharge curves of sodium iron pyrophosphate at different rates, demonstrating good rate performance. Its 1C discharge specific capacity is 91.78 mAh g⁻¹. -1 After cycling at a high rate of 5-20C, the capacity still remains at 89.89mAhg after cycling at 1C. -1 .
[0047] As can be seen from the above embodiments, the composite sodium iron phosphate material with a small amount of other transition metals doped according to the present invention uses organophosphonic acids containing phosphonic acid groups and carbon-containing groups. This provides the phosphorus source required for the synthesis of sodium iron pyrophosphate and also forms amorphous carbon for coating. Simultaneously, purity is improved by controlling the median particle size and pH value. The addition of other transition metals improves electronic conductivity and rate performance. The synthesis process is green, environmentally friendly, safe, and low-cost. Furthermore, the electrode material obtained by this method exhibits high specific capacity and long cycle life.
[0048] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.
Claims
1. A method for synthesizing a composite sodium iron phosphate material, characterized in that, The method comprises the following steps: (1) taking phosphorus source, first part of sodium source and carbon source, adding deionized water and stirring, after the raw materials are dissolved or uniformly dispersed, adding second part of sodium source and iron source, heating and fully reacting, then adding other transition metal source to continue the reaction, to obtain a precursor solution; the precursor solution is fully ground and then dried to obtain a precursor; (2) the precursor obtained in step (1) is sintered in two stages under a protective atmosphere, and after natural cooling, other transition metal doped composite sodium iron phosphate material is obtained.
2. The method of claim 1, wherein the composite sodium iron phosphate material is characterized by: The element molar ratio of each raw material in step (1) satisfies: Na:Fe:other transition metal:P=x:x-1-y:y:x, wherein 3≤x≤4, 0 3. The method for synthesizing a composite sodium iron phosphate material according to claim 2, characterized in that, In step (1): The phosphorus source is at least one of ammonium dihydrogen phosphate, sodium dihydrogen phosphate, ammonium sodium dihydrogen phosphate, sodium phosphate, sodium pyrophosphate, sodium diaminomethyl phosphate, phosphoric acid, hydroxyethylidene diphosphonic acid, aminotri (methylene) phosphonic acid, ethylenediamine tetramethylene phosphonic acid or hexanediamine tetramethylene phosphonic acid, and at least one organic phosphonic acid is contained; The sodium source is at least one of sodium hydroxide, sodium nitrate, sodium carbonate, sodium formate, sodium acetate, sodium ethoxide, sodium gluconate, sodium ascorbate, sodium benzoate, sodium oxalate, sodium malate or sodium citrate, and at least one organic sodium salt is contained.
4. The method for synthesizing a composite sodium iron phosphate material according to claim 3, characterized in that, In step (1): The carbon source is at least one of glucose, citric acid, sucrose, polyethylene glycol, ascorbic acid, maltose, starch, oxalic acid, malic acid or polyvinyl alcohol; The iron source is at least one of ferrous phosphate, ferric phosphate, ferrous oxalate, ferric nitrate, iron powder or iron oxide; The other transition metal source is at least one of sodium metavanadate, divanadium pentoxide, manganese monoxide, manganese dioxide, manganese oxalate, manganese citrate, manganese manganate, manganese hydroxide, nickel hydroxide or cobalt hydroxide.
5. The method for synthesizing a composite sodium iron phosphate material according to claim 4, characterized in that, The temperature of the heating and full reaction in step (1) is 50-100℃, and the mass fraction of the carbon source in the precursor is 2-15%.
6. The method for synthesizing a composite sodium iron phosphate material according to claim 5, characterized in that, After adding the other transition metal source to continue the reaction in step (1), the pH value of the obtained precursor solution is less than 7, and the fully ground condition is that the median particle size of the particles in the precursor solution is ground to below 250nm by using a grinding device.
7. The method for synthesizing a composite sodium iron phosphate material according to claim 6, characterized in that, The drying method in step (1) is at least one of spray drying, vacuum drying or flash drying.
8. The method for synthesizing a composite sodium iron phosphate material according to claim 7, characterized in that, The protective atmosphere in step (2) is at least one of argon, nitrogen or hydrogen-argon mixed gas.
9. The method for synthesizing a composite sodium iron phosphate material according to claim 8, characterized in that, The first stage is sintered at 250-350℃ for 2-6h, and the second stage is sintered at 550-650℃ for 8-12h.
10. A sodium-ion battery of a composite sodium iron phosphate material, characterized in that, The composite sodium iron phosphate material obtained by the synthesis method of claim 9.