A method for preparing sodium manganese iron vanadium phosphate by recycling lithium manganese iron phosphate
By recycling lithium manganese iron phosphate to prepare ferric ammonium manganese phosphate, and then preparing sodium manganese iron vanadium phosphate from ferric ammonium manganese phosphate, the problem of recycling waste lithium manganese iron phosphate cathode material is solved, and high energy density and cycle stability of sodium manganese iron vanadium phosphate as a high-efficiency cathode material for sodium-ion batteries are achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- HEFEI UNIV
- Filing Date
- 2025-07-17
- Publication Date
- 2026-06-26
AI Technical Summary
Existing technologies make it difficult to efficiently recycle and utilize waste lithium iron phosphate cathode materials, and the low energy density of lithium iron phosphate limits its application expansion.
By recycling lithium manganese iron phosphate to prepare ferric ammonium manganese phosphate, and then preparing sodium manganese iron vanadium phosphate from ferric ammonium manganese phosphate, sodium manganese iron vanadium phosphate is prepared using a combination of co-precipitation and solid-state methods, and is used as a raw material for sodium-ion battery cathode materials.
The efficient recycling of waste lithium manganese iron phosphate cathode material has been achieved, and the prepared sodium manganese iron vanadium phosphate exhibits excellent discharge specific capacity and cycle performance as a cathode material for sodium-ion batteries.
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Figure CN120817587B_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of electrode materials technology, and specifically to a method for preparing sodium manganese iron vanadium phosphate by recovering lithium manganese iron phosphate. Background Technology
[0002] The field of lithium-ion battery cathode materials continues to develop, with lithium iron phosphate (LFP) holding a significant market position due to its high safety and long cycle life. However, LFP's relatively low energy density and insufficient low-temperature performance limit its further application expansion. To overcome the performance bottleneck of LFP materials, lithium manganese iron phosphate (MnFeP) has shown significant advantages by partially replacing iron with manganese. Its core improvement lies in its higher energy density, which stems from the increased energy density of MnFeP. 2+ / 3+ Redox couple (~4.1V vs. Li) + / Li) is significantly higher than Fe 2+ / 3+ Redox couple (~3.4V vs. Li) + / Li). Meanwhile, similar to lithium iron phosphate, lithium manganese iron phosphate materials contain stable phosphate groups (PO4). 3- The lithium manganese iron phosphate (LMP) forms a strong covalent bond network, endowing it with excellent structure and thermal stability. Given these technological advantages, LMP is considered one of the most commercially promising cathode materials for the future, especially with huge potential in the electric vehicle and electric motorcycle markets. In the coming years and decades, a large number of spent LMP batteries will inevitably be generated. The LMP cathode material in these discarded batteries contains valuable metals such as lithium, manganese, and iron, and its grade is usually much higher than that of natural ores. Therefore, developing efficient recycling technologies for LMP cathode materials is crucial.
[0003] Sodium-ion batteries have attracted global attention as one of the most promising alternatives to lithium-ion batteries. Given the widespread availability and low cost of sodium, in contrast to depleted resources and the localized distribution of lithium, polyanionic cathodes of the NASICON type have garnered significant interest due to their stable 3D framework structure, which facilitates Na-ion migration. Among possible compositions, vanadium-containing cathode materials have attracted considerable attention due to their high output voltage and maximum available capacity. The fabrication of low-cost and relatively simple vanadium-based materials holds promise for use as electrodes in sodium-ion batteries. However, considering the toxicity and high cost of vanadium, this invention aims to prepare Na₄VMn by replacing one vanadium site with ferroammonium manganese phosphate obtained from the recovery of lithium manganese iron phosphate cathode materials. x Fe 1-x (PO4)3.
[0004] Currently, the publicly disclosed methods for synthesizing sodium manganese iron vanadium phosphate mainly include the sol-gel method and the solid-phase method. The sol-gel method dissolves raw materials such as iron, manganese, vanadium, phosphorus, and sodium sources in water or organic solvents. Local precipitation is prevented by adding chelating agents and adjusting the pH value. This process ensures that metal ions are uniformly dispersed at the atomic level and combine with the phosphorus source to form an amorphous precursor. However, the sol-gel method suffers from drawbacks such as process complexity, high cost, drying shrinkage, and residual impurities, limiting its application in large-scale production and the preparation of high-performance dense materials. The solid-phase method involves uniformly mixing raw materials such as iron, manganese, vanadium, phosphorus, and sodium sources through mechanical ball milling to obtain a manganese iron vanadium phosphate precursor, followed by high-temperature sintering. This synthetic route is simple to operate, and the resulting product has a uniform elemental distribution and precisely adjustable proportions. Mechanical crushing increases the specific surface area of the particles, significantly improving catalytic activity and reaction rate, making it a better synthetic route for industrial applications. Summary of the Invention
[0005] The technical problem to be solved by the present invention is to provide a method for preparing sodium manganese iron vanadium phosphate by recycling lithium manganese iron phosphate. First, iron ammonium manganese phosphate is prepared by using waste lithium manganese iron phosphate cathode material, and then sodium manganese iron vanadium phosphate is prepared from iron ammonium manganese phosphate, thereby realizing the efficient recycling and utilization of waste lithium manganese iron phosphate cathode material.
[0006] The technical problem to be solved by this invention is achieved by the following technical solution:
[0007] One objective of this invention is to provide a method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate, comprising the following steps:
[0008] S1. Add sodium source, vanadium source, iron source, phosphorus source and carbon source to manganese iron ammonium phosphate, mix evenly, dry to obtain the precursor;
[0009] S2. The precursor is calcined, cooled, washed, and dried to obtain sodium manganese iron vanadium phosphate.
[0010] Furthermore, the sodium source is at least one of sodium acetate and sodium carbonate.
[0011] Furthermore, the vanadium source is vanadium pentoxide.
[0012] Furthermore, the iron source is ferrous oxalate.
[0013] Furthermore, the phosphorus source is ammonium dihydrogen phosphate.
[0014] Furthermore, the carbon source is at least one of citric acid and polyethylene glycol. In this invention, the carbon source is added in two stages and ball-milled twice accordingly, the purpose of which is to control the particle size of the precursor.
[0015] Furthermore, the molar ratio of the manganese iron ammonium phosphate, sodium source, vanadium source, iron source, and phosphorus source is 0.67:4.4:0.5:0.33:2.45. Sodium manganese iron vanadium phosphate synthesized according to this molar ratio will only produce sodium phosphate impurities, which can be removed by washing with water.
[0016] Furthermore, the amount of carbon source used is 15-20% of the total mass of the raw materials, where the total mass of the raw materials refers to the total mass of manganese iron ammonium phosphate, sodium source, vanadium source, iron source, phosphorus source, and carbon source. Preferably, the carbon source is composed of citric acid and polyethylene glycol (PEG) in a mass ratio of (1-2):1.
[0017] Furthermore, the mixing method is ball milling at a speed of 500–700 rpm. The purpose of ball milling is to thoroughly mix the raw materials and reduce the particle size of the precursors.
[0018] Furthermore, the drying method is vacuum drying, with a drying temperature of 85–100°C and a drying time of 10–12 hours. The purpose of vacuum drying is to prevent the ferrous and manganese ions in the raw materials from being oxidized to trivalent ions in the air.
[0019] Furthermore, the calcination atmosphere is an argon-hydrogen mixture, wherein the volume fraction of hydrogen is 5-10%.
[0020] Furthermore, the calcination temperature is 650–750℃, the heating rate is 2–5℃ / min, and the holding time is 10–12 h. Calcination can be performed once or twice.
[0021] Furthermore, the calcination is divided into two stages. The first stage calcination temperature is 300-400℃, the heating rate is 2-5℃ / min, and the holding time is 2-3h. The second stage calcination temperature is 650-750℃, the heating rate is 2-5℃ / min, and the holding time is 10-12h.
[0022] Furthermore, the washing process includes washing with deionized water and washing with anhydrous ethanol. In this invention, impurities such as sodium phosphate are removed through washing.
[0023] Furthermore, the molecular formula of the sodium manganese iron vanadium phosphate is Na₄VMn. 0.5 Fe 0.5 (PO4)3.
[0024] The second objective of this invention is to provide a method for preparing ferric ammonium manganese phosphate using waste lithium manganese iron phosphate cathode material, comprising the following steps:
[0025] (1) The waste lithium manganese iron phosphate cathode material was acid-leached and filtered to obtain the leachate;
[0026] (2) Slowly introduce ammonia into the leachate to adjust the pH value to weak acidity or weak alkalinity. After the pH stabilizes, introduce inert gas, age, filter, wash, and dry to obtain manganese iron ammonium phosphate.
[0027] Furthermore, the acid used for acid leaching is sulfuric acid with a concentration of 1.3–2 mol / L.
[0028] Furthermore, the solid-liquid ratio of the acid leaching is 1:(5-10), the stirring speed is 300-400 rpm, the temperature is 70-85℃, and the time is 2-4 h.
[0029] Furthermore, the molar ratio of manganese, iron, and phosphorus in the leachate is 3:2:5.
[0030] The purpose of acid leaching is to ensure that all valuable metal ions can dissolve in the acid solution. Iron and manganese ions both exist in the divalent state, and the molar ratio of manganese, iron, and phosphorus in the leachate remains at 3:2:5 compared to the raw materials.
[0031] Furthermore, the weak acidity is pH 5-6; the weak alkalinity is pH 5-9. Ammonia is introduced to provide sufficient NH4+. + This allows metal ions in the solution to combine with it and precipitate, and ammonia can also balance the pH value of the solution.
[0032] Furthermore, the inert gas is nitrogen or argon. The purpose of introducing the inert gas is to avoid the oxidation of ferrous iron and ferrous manganese.
[0033] Furthermore, the aging process involves stirring at 300–400 rpm, at a temperature of 50–60°C, and for 2–6 hours. During the stirring and heating process, metal ions react with NH4+ in the solution. + and PO4 3- By combining the resulting iron manganese ammonium phosphate, iron, manganese, and phosphorus can be efficiently converted into the product, greatly improving atom economy and resource reusability.
[0034] Furthermore, the drying method is vacuum drying, the drying temperature is 85-100℃, and the drying time is 10-12 hours.
[0035] Furthermore, the washing is performed with deionized water. This water washing removes ammonium sulfate, which is formed by the reaction of sulfuric acid and ammonia.
[0036] Furthermore, the molecular formula of the iron manganese phosphate is NH4Mn. 0.6 Fe 0.4 PO4.
[0037] The beneficial effects of this invention are: This invention utilizes a co-precipitation method to prepare ferric ammonium manganese phosphate from waste lithium manganese iron phosphate cathode material. The ferric ammonium manganese phosphate has high purity, no impurities, and a columnar structure. Using ferric ammonium manganese phosphate as a raw material, high-purity sodium manganese iron vanadium phosphate can be prepared and used as a cathode material for sodium-ion batteries, enabling sodium-ion batteries to have excellent discharge specific capacity, rate performance, and cycle performance. Attached Figure Description
[0038] Figure 1 The X-ray diffraction (XRD) pattern of the ferric ammonium manganese phosphate prepared in Example 1;
[0039] Figure 2 The image shows a scanning electron microscope (SEM) image of the ferric ammonium manganese phosphate prepared in Example 1.
[0040] Figure 3 The XRD pattern of sodium manganese iron vanadium phosphate prepared in Example 2;
[0041] Figure 4 Capacity-voltage diagram and cycle performance diagram of a coin cell assembled using sodium manganese iron vanadium phosphate prepared in Example 2 as the positive electrode material of a sodium-ion battery.
[0042] Figure 5 The capacity-voltage diagram shows the coin cell assembled using sodium manganese iron vanadium phosphate prepared in Comparative Example 1 as the positive electrode material for a sodium-ion battery. Detailed Implementation
[0043] 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 and illustrations.
[0044] Example 1
[0045] 10g of waste lithium manganese iron phosphate cathode material powder was dissolved in 100mL of dilute sulfuric acid (concentration 1.5mol / L), and acid leaching was carried out for 4h under the conditions of stirring speed 300rpm and temperature 85℃. After filtration, the leachate was obtained. The molar ratio of manganese, iron and phosphorus elements was 3:2:5.
[0046] 25% ammonia solution was slowly passed into the above leachate to adjust the pH to 5-6, and the solution was stirred at room temperature. After the pH stabilized, nitrogen gas was introduced, and the solution was aged for 2 hours at a stirring speed of 300 rpm and a temperature of 60°C. Ammonia solution was then added to maintain the pH at 5-6, and aging was continued for another 2 hours at a stirring speed of 300 rpm and a temperature of 60°C. The product was washed with deionized water, filtered, and vacuum dried at 85°C for 12 hours to obtain ferric manganese phosphate.
[0047] XRD and SEM analyses were performed on the ammonium iron manganese phosphate prepared in Example 1, and the results are as follows: Figure 1 and Figure 2 As shown.
[0048] according to Figure 1 The XRD analysis results show that the diffraction peak angle of the product prepared in Example 1 is located between the characteristic peaks of ferric ammonium phosphate and manganese ammonium phosphate, which proves that NH4Mn 0.6 Fe 0.4 Successful synthesis of PO4.
[0049] according to Figure 2 The SEM scanning results show that the iron manganese phosphate prepared in Example 1 has a columnar structure with a diameter of 10-20 μm.
[0050] Example 2
[0051] Take 0.2248g of the manganese iron ammonium phosphate prepared in Example 1, and add 0.7218g of sodium acetate, 0.1818g of vanadium pentoxide, 0.5634g of ammonium dihydrogen phosphate, 0.1198g of ferrous oxalate and 0.2209g of citric acid to make the elemental molar ratio of sodium, vanadium, manganese, iron and phosphorus 4.4:1:0.4:0.6:3.015. Crush and mix all raw materials in a mortar, then place them in a ball mill jar, add deionized water to moisten, ball mill at 500 rpm for 6 hours, vacuum dry at 100°C for 12 hours, then add 0.2209g of PEG400, ball mill at 500 rpm for 6 hours, vacuum dry at 100°C for 12 hours to obtain the precursor.
[0052] The above precursor was placed in a tube furnace and an argon-hydrogen mixed gas was introduced, wherein the volume fraction of hydrogen was 5%. The calcination was divided into two stages. The first stage calcination temperature was 350℃, the heating rate was 5℃ / min, and the holding time was 2h. The second stage calcination temperature was 750℃, the heating rate was 5℃ / min, and the holding time was 10h. After natural cooling to room temperature, the product was washed multiple times with deionized water and anhydrous ethanol, filtered, and vacuum dried at 85℃ for 12h to obtain sodium manganese iron vanadium phosphate.
[0053] XRD analysis was performed on the sodium manganese iron vanadium phosphate prepared in Example 2. The XRD analysis results are as follows: Figure 3 As shown.
[0054] according to Figure 3 The XRD analysis results show that the diffraction peak angles of the product prepared in Example 2 match those of the standard card, and Figure 4 The charge-discharge curves show the charge-discharge plateaus of V, Mn, and Fe, which proves that Na4VMn 0.5 Fe 0.5 Successful synthesis of (PO4)3.
[0055] Example 3
[0056] The preparation of ferric ammonium manganese phosphate was carried out according to the method of Example 1, except that the amount of dilute sulfuric acid was adjusted to 100 mL and the concentration was adjusted to 1.5 mol / L.
[0057] Example 4
[0058] The preparation of ferric manganese phosphate was carried out according to the method of Example 1, except that the aging time was adjusted to 6 hours.
[0059] Example 5
[0060] The method of Example 1 was followed to prepare ferric ammonium manganese phosphate, except that ammonia water was introduced to adjust the pH to 8-9.
[0061] Example 6
[0062] Sodium manganese iron vanadium phosphate was prepared according to the method in Example 2, except that sodium acetate was replaced with sodium carbonate, and only citric acid was used as the carbon source.
[0063] Example 7
[0064] Sodium manganese iron vanadium phosphate was prepared according to the method in Example 2, except that only one calcination was performed.
[0065] The calcination temperature was 750℃, the heating rate was 5℃ / min, and the holding time was 10h.
[0066] Comparative Example 1
[0067] Sodium manganese ferrovanadium phosphate was prepared according to the method in Example 2, except that ferrous oxalate was not added to adjust the manganese-iron ratio. All the manganese and ferric phosphate were derived from the ammonium manganese ferrovanadium phosphate prepared in Example 1. At this time, the molar ratio of manganese and ferric phosphate was 3:2, and the synthesized product was Na₄VMn. 0.6 Fe 0.4 (PO4)3.
[0068] Sodium manganese iron vanadium phosphate prepared in Example 2 and Comparative Example 1 were used as cathode materials for sodium-ion batteries, respectively. Coin cells were assembled, and their electrochemical performance was tested. Capacity-voltage diagrams and cycle performance diagrams are shown below. Figure 4 , Figure 5 As shown.
[0069] Assembly process of button cell: The positive electrode active material (sodium manganese iron vanadium phosphate prepared in Example 2 or Comparative Example 1), conductive carbon black (Super P), and polyvinylidene fluoride are mixed with solvent N-methylpyrrolidone in a mass ratio of 7:2:1. The mixed slurry is evenly coated on aluminum carbon foil and dried in a vacuum oven at 85°C for 12 hours. After cutting, the mass loading of the positive electrode active material on the electrode sheet is 1 mg / cm³. 2The CR2016 button cell was assembled using glass fiber (Whatman, GF / D) as the separator, sodium metal sheet as the negative electrode, and a 1 mol / mL sodium hexafluorophosphate solution as the electrolyte (sodium hexafluorophosphate was dissolved in a mixed solvent of propylene carbonate and ethylene carbonate, with a volume ratio of 1:1). The assembly was carried out in a glove box filled with argon atmosphere (H2O and O2 content below 0.1 ppm).
[0070] Depend on Figure 4 , Figure 5 It can be seen that the coin cell assembled using sodium manganese iron vanadium phosphate prepared in Example 2 as the positive electrode material of a sodium-ion battery has a discharge capacity of 107.8 mAh g at a 0.5C rate. -1 After 1000 cycles at 5C, the capacity retention rate was 60%; while the coin cell assembled using sodium manganese iron vanadium phosphate prepared in Comparative Example 1 as the positive electrode material for sodium-ion batteries had a discharge specific capacity of only 88.1 mAh g at 0.5C. -1 .
[0071] In summary, the sodium manganese iron vanadium phosphate prepared according to the method provided by this invention has a high specific capacity and excellent cycle performance, while realizing the efficient recycling of waste lithium manganese iron phosphate cathode materials.
[0072] 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 preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate, characterized in that, Includes the following steps: S1. Add sodium source, vanadium source, iron source, phosphorus source and carbon source to manganese iron ammonium phosphate, mix evenly, dry to obtain the precursor; S2. The precursor is calcined, cooled, washed, and dried to obtain sodium manganese iron vanadium phosphate. The molar ratio of the manganese iron ammonium phosphate, sodium source, vanadium source, iron source, and phosphorus source is 0.67 : 4.4 : 0.5 : 0.33 : 2.45; The amount of carbon source used is 15-20% of the total mass of the raw materials; The carbon source is composed of citric acid and polyethylene glycol in a mass ratio of (1~2):1; The calcination temperature is 650~750℃, the heating rate is 2~5℃ / min, and the holding time is 10~12 h; The preparation method of the ferric ammonium manganese phosphate includes the following steps: (1) The waste lithium manganese iron phosphate cathode material was acid-leached and filtered to obtain the leachate; (2) Slowly introduce ammonia into the leachate to adjust the pH value to weak acidity or weak alkalinity. After the pH stabilizes, introduce inert gas, age, filter, wash, and dry to obtain manganese iron ammonium phosphate.
2. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The sodium source is at least one of sodium acetate and sodium carbonate.
3. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The vanadium source is vanadium pentoxide.
4. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The iron source is ferrous oxalate.
5. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The phosphorus source is ammonium dihydrogen phosphate.
6. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The carbon source is at least one of citric acid and polyethylene glycol.
7. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The mixing method is ball milling, with a ball milling speed of 500~700 rpm.
8. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The drying method is vacuum drying, with a drying temperature of 85~100℃ and a drying time of 10~12 h.
9. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The calcination atmosphere is an argon-hydrogen mixture, wherein the volume fraction of hydrogen is 5-10%.
10. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The calcination is divided into two stages. The first stage calcination temperature is 300~400℃, the heating rate is 2~5℃ / min, and the holding time is 2~3 h. The second stage calcination temperature is 650~750℃, the heating rate is 2~5℃ / min, and the holding time is 10~12 h.
11. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The molecular formula of the sodium manganese iron vanadium phosphate is Na₄VMn. 0.5 Fe 0.5 (PO4)3.
12. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The acid used for acid leaching is sulfuric acid with a concentration of 1.3~2 mol / L.
13. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The solid-liquid ratio of the acid leaching is 1:(5~10), the stirring speed is 300~400 rpm, the temperature is 70~85℃, and the time is 2~4 h.
14. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The molar ratio of manganese, iron, and phosphorus in the leachate is 3:2:
5.
15. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The weak acidity is pH 5-6; the weak alkalinity is pH 8-9.
16. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The inert gas is nitrogen or argon.
17. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The aging process involves stirring at 300-400 rpm, at a temperature of 50-60℃, and for 2-6 hours.
18. The method for preparing sodium manganese iron vanadium phosphate using lithium manganese iron phosphate according to claim 1, characterized in that: The molecular formula of the ferric manganese phosphate is NH4Mn 0.6 Fe 0.4 PO4.