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CN-122010080-A - Preparation method of polyanionic sodium iron phosphate positive electrode material for non-negative sodium ion battery

CN122010080ACN 122010080 ACN122010080 ACN 122010080ACN-122010080-A

Abstract

The invention discloses a preparation method of a polyanion type sodium iron phosphate positive electrode material for a non-negative sodium ion battery, which comprises the following steps of S1, preparing precursor slurry, S4, sintering at a high temperature under a protective atmosphere to obtain an iron-based phosphate positive electrode material suitable for the non-negative sodium ion battery, wherein an iron source, a quick sodium source, a slow sodium source and a phosphorus source are weighed according to stoichiometric ratio, a carbon source is mixed in a solvent, the pH value of the solution is controlled to form uniform precursor slurry, S2, bimetal doping is introduced, a magnesium source and a titanium source are added, the total doping amount of Mg and Ti is controlled to be the proportion of Fe sites, the mixing is uniform, the doped precursor slurry is obtained, S3, presintering is carried out after the slurry is dried, a stable precursor structure is formed, and S4, sintering at a high temperature is carried out. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the non-negative sodium ion battery has the characteristics of good structural stability, high pure phase formation and excellent electrochemical performance.

Inventors

  • LIU MENGZHU
  • ZHAO ALONG
  • CAO YULIANG
  • ZHU XUANYI
  • GAO ZHEN

Assignees

  • 深圳珈钠能源科技有限公司

Dates

Publication Date
20260512
Application Date
20260215

Claims (10)

  1. 1. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the non-negative sodium ion battery is characterized by comprising the following steps of: S1, preparing precursor slurry, namely weighing an iron source, a fast sodium source, a slow sodium source and a phosphorus source according to stoichiometric ratio, mixing a carbon source in a solvent, and controlling the pH value of the solution to form uniform precursor slurry; s2, introducing bimetal doping, namely adding a magnesium source and a titanium source into the precursor slurry, controlling the total doping amount of Mg and Ti to be the proportion of Fe sites, and uniformly mixing to obtain the doped precursor slurry; s3, presintering, namely drying the doped precursor slurry and presintering to form a stable precursor structure; and S4, high-temperature sintering, namely performing high-temperature sintering under a protective atmosphere to obtain the iron-based phosphate anode material suitable for the negative-electrode-free sodium ion battery.
  2. 2. The method for preparing a polyanionic sodium iron phosphate positive electrode material for a non-negative sodium ion battery according to claim 1, wherein in step S1, the pH of the precursor slurry is controlled to be in a range of 6.0-8.0.
  3. 3. The method for preparing a polyanionic sodium iron phosphate positive electrode material for a non-negative sodium ion battery according to claim 1, wherein in the step S2, the total doping amount of Mg and Ti is 0.3-2.5% of Fe site.
  4. 4. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the non-negative sodium ion battery, which is disclosed in claim 1, is characterized in that in the step S3, the presintering condition is that the presintering temperature is 280-450 ℃, the heating rate is 0.5-3.0 ℃ per minute, and the heat preservation time is 2-8 hours.
  5. 5. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the non-negative sodium ion battery according to claim 1, wherein in the step S4, the high-temperature sintering condition is that the high-temperature sintering temperature is 600-720 ℃, the heating rate is 1-3 ℃ per minute, and the heat preservation time is 6-14h. The protective atmosphere is nitrogen and/or argon.
  6. 6. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the negative electrode-free sodium ion battery according to claim 1, wherein in the step S1, the rapid sodium release source is one or more than two of NaH 2 PO 4 ·2H 2 O、NaH 2 PO 4 、Na 2 HPO 4 、CH 3 COONa, the slow sodium release source is one or more than two of Na 4 P 2 O 7 、Na 3 PO 4 、Na 2 CO 3 、NaHCO 3 、NH 4 H 2 PO 4 、(NH 4 ) 2 HPO 4 、H 3 PO 4 、NaH 2 PO 4 、Na 2 HPO 4 、Na 4 P 2 O 7 , and the molar quantity of sodium provided by the rapid sodium release source accounts for 30-70% of the total molar quantity of sodium.
  7. 7. The method for preparing a polyanionic sodium iron phosphate positive electrode material for a non-negative sodium ion battery according to claim 1, wherein in the step S1, the molar ratio of Fe to P in the iron source and the phosphorus source is 2.90:4.00-3.10:4.00.
  8. 8. The method for preparing a polyanionic sodium iron phosphate positive electrode material for a non-negative sodium ion battery according to claim 1, wherein in the step S1, the molar ratio of Na to P in the sodium source to the phosphorus source is 0.98:1.00-1.05:1.00.
  9. 9. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the negative electrode-free sodium ion battery of claim 1, wherein in the step S1, the carbon source is one or more than two of phenolic resin, epoxy resin, polydopamine, asphalt precursor, petroleum coke sol, polystyrene and polyvinyl alcohol, and the addition amount of the carbon source is 0.5-3.0wt%.
  10. 10. The preparation method of the polyanionic sodium iron phosphate positive electrode material for the non-negative sodium ion battery of claim 9, wherein the iron source is one or more than two of FeC 2 O 4 ·2H 2 O、FePO 4 ·xH 2 O、Fe(NO 3 ) 3 ·9H 2 O、Fe(CH 3 COO) 2 、FeSO 4 ·7H 2 O、Fe 2 (SO 4 ) 3 、FeOOH、Fe 2 O 3 ; the phosphorus source is one or more than two of Na 4 P 2 O 7 、Na 3 PO 4 、Na 2 CO 3 、NaHCO 3 、NH 4 H 2 PO 4 、(NH 4 ) 2 HPO 4 、H 3 PO 4 、NaH 2 PO 4 、Na 2 HPO 4 、Na 4 P 2 O 7 ; The magnesium source is one or more than two of Mg(CH 3 COO) 2 ·4H 2 O、Mg(NO 3 ) 2 ·6H 2 O、MgSO 4 ·7H 2 O、MgCl 2 ·6H 2 O、Mg(OH) 2 、MgO; the titanium source is one or more than two of TiO 2 、Ti(SO 4 ) 2 、TiCl 4 , butyl titanate and isopropyl titanate.

Description

Preparation method of polyanionic sodium iron phosphate positive electrode material for non-negative sodium ion battery Technical Field The invention relates to the technical field of sodium ion batteries, in particular to a preparation method of a polyanion type sodium iron phosphate positive electrode material for a non-negative sodium ion battery. Background Along with the increasingly prominent problems of lithium resource price fluctuation and uneven reserve distribution, the sodium ion battery gradually becomes an important supplementary technical route of the lithium ion battery due to the advantages of abundant sodium resources, low cost, environmental friendliness and the like. In the current sodium ion battery system, the positive electrode material mainly comprises layered oxide, prussian blue compounds and polyanion compounds. Among them, the polyanionic cathode material is considered as an important development direction in a scene with high safety requirements due to its stable three-dimensional framework structure, higher working voltage and good thermal stability. Among the polyanionic cathode materials, na 4Fe3(PO4)2(P2O7) (NFPP) has been attracting attention in recent years because of the advantages of low cost, good safety, high theoretical capacity, and the like of its iron-based system. NFPP A skeleton structure is formed by PO 4 & lt- & gt and P 2O74 & lt- & gt together, fe2+/Fe3 & lt+ & gt is taken as a main redox pair, the deintercalation sodium potential is 3.2-3.4V (vs Na/Na+), and good cycle stability is shown in a conventional sodium ion battery. However, the research and industrialization of NFPP are almost all based on the conventional negative sodium ion battery system, i.e. the negative side adopts sodium-embedded materials such as hard carbon. Under the system, the cathode generally has a certain sodium stock and buffer capacity, and partial irreversible sodium loss generated in the first charge and discharge process of the anode can be compensated to a certain extent through cathode redundancy or an electrolyte system. Therefore, the existing NFPP technology focuses more on the rate capability, the cycle life and the high-temperature stability, but focuses less on the problems of first effect, sodium loss mechanism, voltage platform smoothness and the like. In recent years, in order to further improve the mass energy density and the volume energy density of sodium ion batteries, academia and industry have begun to search for negative-electrode-free sodium ion battery systems. In the system, no anode active material is configured in an initial state, only a metal current collector is reserved, and sodium ions separated from the anode in the first charging process are subjected to metal sodium deposition on the surface of the anode. The technical route can obviously reduce the dosage of the anode material and the complexity of the process, and theoretically has a higher upper limit of energy density. However, negative-electrode-free sodium-ion battery systems place unprecedented stringent demands on the positive electrode material. Since the source of sodium ions in the battery system is completely dependent on the positive electrode, any irreversible sodium loss can be directly converted into a battery capacity loss, and the first coulombic efficiency of the positive electrode material almost determines the usable life of the battery. Meanwhile, the non-uniformity of the positive electrode sodium removal behavior can cause fluctuation of the deposition rate of sodium metal on the negative electrode side, dendrite growth and formation of dead sodium are easy to be induced, and the safety and the cycling stability of the battery are seriously affected. When the existing NFPP material is applied to a non-negative electrode system, the following problems generally exist: If the sodium source is dissolved and the reaction rate is mismatched in the preparation process, free sodium species such as Na 2CO3, naOH and the like are easily formed on the surface or a crystal boundary of the material, and are irreversibly consumed in the first-circle reaction; If the difference of the deintercalation energy barriers of different sodium sites in the Fe-O-P skeleton is large, the deintercalation process is performed in multiple stages, and a voltage curve has saw teeth or slopes; For example, glucose, citric acid and other carbon sources which are easy to form a porous carbon layer with high specific surface area are often used for conventional carbon coating, and the carbon source is favorable for multiplying power performance, but side reactions can be obviously aggravated in a cathode-free system, and valuable sodium inventory is consumed. Disclosure of Invention The invention aims to provide a preparation method of a polyanionic sodium iron phosphate positive electrode material for a non-negative sodium ion battery, which has the characteristics of good structural stability, high pure p