Preparation method of layered oxide positive electrode material of sodium-ion battery

Abstract

The invention provides a preparation method of a layered oxide positive electrode material of a sodium-ion battery, which comprises the following steps: accurately weighing an iron-manganese binary precursor NaaFexMn1-yO2 and a sodium source compound according to the molar ratio of each element in a chemical general formula, adding a fluxing agent and a lattice dopant, and then fully mixing in a dry mixing manner to obtain a dispersed mixture; s2, sintering the dispersed mixture obtained in the step S1 for the first time in an oxygen-enriched atmosphere, and then cooling, crushing, grading and sieving to obtain sintered powder; and S2, fully mixing the sintered powder obtained in the step S2 with a coating agent, sintering for the second time in an oxygen-enriched atmosphere, and then cooling, crushing, grading and sieving to prepare the layered oxide positive electrode material of the sodium-ion battery. The components are dispersed uniformly, element blending is accurate, the prepared positive electrode material is excellent in performance, meanwhile, the whole technological process does not need to use an organic solvent or generate harmful wastewater, and the requirement for environmental protection is completely met.

Description

Technical Field

[0001] This application belongs to the field of electrochemical technology, and in particular relates to a method for preparing a layered oxide cathode material for sodium-ion batteries. Background Technology

[0002] With the accelerated global energy structure transformation, the demand for large-scale, low-cost energy storage systems is becoming increasingly urgent. Sodium-ion batteries, due to their significant advantages of widely available raw materials and low cost, have become one of the ideal energy storage technologies to support the grid connection of renewable energy and the development of smart grids. Among many sodium-ion battery cathode materials, iron-manganese-based transition metal oxides (Na₂O₃) are particularly suitable. a Fe x Mn 1- y O2 is considered one of the cathode material systems with the greatest potential for large-scale commercial application because it combines the low cost and environmental friendliness of iron with the high operating voltage and high capacity of manganese.

[0003] However, this material system still faces severe challenges in its actual industrial-scale preparation. The currently commonly used solid-state synthesis process, which involves mechanically and dryly mixing powders such as sodium, iron, and manganese oxides or carbonates and then directly sintering them at high temperatures, has inherent limitations.

[0004] First, because iron and manganese raw materials are difficult to disperse uniformly at the atomic scale, local components in the final product deviate from the stoichiometry, easily forming impurity phases. This inhomogeneity can cause inconsistent phase transition behavior during charge and discharge, severely impairing the cycling stability and batch consistency of the material.

[0005] Secondly, manganese is prone to disproportionation reactions during high-temperature sintering, leading to the loss of active materials and degradation of the interfacial structure, thus accelerating capacity decay. Traditional dry mixing processes, due to insufficient contact, may actually exacerbate localized manganese enrichment, accelerating this side reaction.

[0006] Furthermore, this process is extremely sensitive to the sintering regime. Incompletely mixed precursors, during sintering, result in uneven reactions between the sodium source and transition metal oxides, easily leading to excessive or insufficient local sodium volatilization. This causes uncontrolled sodium vacancy order and irreversible phase transitions, reducing not only the initial material volume but also its structural stability. Simultaneously, the dust generated during the process poses a potential threat to the production environment and the health of operators.

[0007] Therefore, developing a preparation method that can achieve molecular-level uniform mixing, precise control of stoichiometry, and effective suppression of manganese dissolution and harmful phase transitions is crucial for overcoming the performance bottleneck of iron-manganese-based layered oxide cathode materials. This method should also be simple, environmentally friendly, and easily scaled up to meet the urgent demand of the future large-scale energy storage market for high-performance, low-cost sodium-ion batteries. Summary of the Invention

[0008] In order to solve at least one of the above-mentioned technical problems and to develop a preparation process that is relatively simple, has relatively uniform dispersion of components, relatively precise element adjustment, and produces a cathode material with excellent performance, this application provides a method for preparing a layered oxide cathode material for sodium-ion batteries.

[0009] On one hand, this application provides a method for preparing a layered oxide cathode material for sodium-ion batteries, wherein the main component of the cathode material has the general chemical formula Na. a Fe x Mn 1-y O2, where 0.30≤a≤0.80, 0.2≤x≤0.8, 0.2≤y≤0.8; The method includes the following steps: S1, the iron-manganese binary precursor Fe x Mn 1-y (OH)2 and sodium source compound were precisely weighed according to the molar ratio of each element in the general chemical formula, and flux and lattice dopant were added. Then, they were thoroughly mixed by dry mixing to obtain a dispersion mixture. S2: The dispersion mixture obtained in step S1 is sintered for the first time in an oxygen-rich atmosphere at a sintering temperature of 880~980℃ and a holding time of 8~15h. Then it is cooled, crushed, graded and sieved to obtain sintered powder. S3: After thoroughly mixing the sintered powder obtained in step S2 with the coating agent, the mixture is sintered for the second time in an oxygen-rich atmosphere at a temperature of 500~750℃ and a holding time of 4~8h. Then, the mixture is cooled, pulverized, graded, and sieved to obtain the layered oxide cathode material for sodium-ion batteries.

[0010] As a preferred embodiment of the present invention, in step S1, the sodium element and the total molar amount of transition metal elements are weighed precisely according to a ratio of 1:0.3~1.0.

[0011] In a preferred embodiment of the present invention, in step S1, the sodium source is selected from one or more of sodium carbonate, sodium hydroxide, and sodium nitrate.

[0012] As a preferred embodiment of the present invention, in step S1, the flux is selected from one or more of boric acid, boron oxide, ammonium molybdate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, barium oxide, calcium oxide, and tungsten oxide, and the total mass of the flux accounts for 0.01% to 1% of the total mass of the precursor and the sodium source.

[0013] As a preferred embodiment of the present invention, in step S1, the lattice dopant is selected from one or more of the oxides, carbonates, and hydroxides of magnesium, aluminum, titanium, zinc, copper, aluminum, and lithium, and the total mass of the lattice dopant accounts for 0.1% to 7.0% of the total mass of the precursor and the sodium source.

[0014] As a preferred embodiment of the present invention, in step S2, the particle size of the powder sieved is within 400 mesh.

[0015] As a preferred embodiment of the present invention, in step S3, the coating agent is selected from one or more of alumina, aluminum phosphate, titanium dioxide, and zirconium oxide, and the total mass of the coating agent elements accounts for 0.1% to 1.5% of the total mass of the sintered powder obtained in step S2.

[0016] As a preferred embodiment of the present invention, in step S3, the median particle size D50 of the obtained sodium-ion battery layered oxide cathode material is controlled to be 3.0~8.0 μm through grading and sieving.

[0017] As a preferred embodiment of the present invention, in steps S2 and S3, the oxygen-enriched atmosphere is pure oxygen or an oxygen-nitrogen mixture with an oxygen volume concentration of not less than 20%.

[0018] On the other hand, this application provides a method for preparing the above-mentioned layered oxide cathode material for sodium-ion batteries, and the obtained layered oxide cathode material for sodium-ion batteries.

[0019] Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. Significantly improved material structural stability and electrochemical performance: This invention utilizes a binary iron-manganese layered oxide system (Na... a Fe x Mn 1-y By precisely controlling the stoichiometry and combining a two-step sintering process under an oxygen-rich atmosphere of high-temperature primary sintering (880-980℃) and medium-temperature secondary sintering (500-750℃), the full growth and crystallization of single crystal particles are effectively promoted, reducing lattice defects and sodium vacancies. This results in a more stable crystal structure and lower surface energy in the prepared single crystal material, which significantly suppresses phase transitions and particle cracks during battery cycling, thus contributing to higher capacity retention and longer cycle life.

[0020] 2. Effective suppression of manganese dissolution and interfacial side reactions: This invention employs a synergistic strategy of introducing lattice dopants (such as Mg, Al, Ti, Zn) and surface coating treatments (such as Al2O3, TiO2, ZrO2) to stabilize the material structure at both the bulk and surface levels. The dopant elements entering the lattice help suppress the Jahn-Teller effect and manganese dissolution during the charging and discharging process. Furthermore, the uniform nano-coating layer directly isolates the positive electrode material from direct contact with the electrolyte, reducing interfacial side reactions and giving the electrode material better rate performance and storage stability.

[0021] 3. Strong process controllability and good product consistency: This invention adopts a route combining dry mixing and solid-state sintering. By precisely controlling the molar ratio of sodium source to transition metal precursor, the amount of flux and dopant added, and the staged sintering temperature and time, the process has high repeatability and is easy to scale up for production. Moreover, the median particle size (D50) of the prepared single crystal cathode material is controlled at 3.0~8.0μm, with uniform particle size distribution and high tap density, which is beneficial to electrode coating processing and can effectively ensure batch consistency and reliability.

[0022] 4. Low cost and environmentally friendly: This invention is based on a binary system rich in iron and manganese, avoiding the use of expensive elements such as cobalt and nickel, thus significantly reducing raw material costs. Furthermore, the sodium source, flux, and coating agent used are all common chemical raw materials with wide availability, and the entire process does not require the use of organic solvents or the generation of harmful wastewater, meeting the requirements of green and environmentally friendly industrial production. Attached Figure Description

[0023] Figure 1 This is an electron microscope image of Example 2 in this invention; Figure 2 This is an electron microscope image of Comparative Example 1 in this invention; Figure 3 The graph shows the electrode compaction density test results for Comparative Example 1 and Example 2 of this application; Figure 4 The graph shows the results of the first discharge specific capacity test at 0.1C for Comparative Example 1 and Example 2 of this application. Figure 5 The graph shows the capacity retention rate test results for Comparative Example 1 and Example 2 of this application after 50 cycles. Detailed Implementation

[0024] The present invention will be further described below with reference to specific embodiments, so that those skilled in the art can better understand and implement the present invention, but the embodiments are not intended to limit the present invention. The present invention will be further described below through embodiments.

[0025] This application provides a method for preparing a layered oxide cathode material for sodium-ion batteries, wherein the main component of the cathode material has the general chemical formula Na. a Fe x Mn 1-y O2, where 0.30≤a≤0.80, 0.2≤x≤0.8, 0.2≤y≤0.8; The method includes the following steps: S1, the iron-manganese binary precursor Fe x Mn 1-y (OH)2 and sodium source compound were precisely weighed according to the molar ratio of each element in the general chemical formula, and flux and lattice dopant were added. Then, they were thoroughly mixed by dry mixing to obtain a dispersion mixture. S2: The dispersion mixture obtained in step S1 is sintered for the first time in an oxygen-rich atmosphere at a sintering temperature of 880~980℃ and a holding time of 8~15h. Then it is cooled, crushed, graded and sieved to obtain sintered powder. S3: After thoroughly mixing the sintered powder obtained in step S2 with the coating agent, the mixture is sintered for the second time in an oxygen-rich atmosphere at a temperature of 500~750℃ and a holding time of 4~8h. Then, the mixture is cooled, pulverized, graded, and sieved to obtain the layered oxide cathode material for sodium-ion batteries.

[0026] The following are embodiments of this application. Example 1 : This embodiment provides a chemical formula Na 0.5 Fe 0.5 Mn 0.5 The specific steps for preparing single-crystal O2 cathode materials are as follows: (1) Weigh the iron-manganese binary precursor Fe precisely according to the target stoichiometric ratio. 0.5 Mn 0.5 (OH)₂ (D50 = 4.0 μm) and sodium carbonate (Na₂CO₃) were used, with the total molar ratio of sodium (Na) to transition metal (Fe + Mn) controlled at 1:0.5. Simultaneously, 0.1% of the total mass of the precursor and sodium source was added as flux boric acid (H₃BO₃), and 1.0% of the total mass of the precursor and sodium source was added as lattice dopant magnesium oxide (MgO).

[0027] (2) Place all the above raw materials in a high-speed mixer and dry mix at 800 rpm for 2 hours to ensure that the mixture is uniform.

[0028] (3) Transfer the uniformly mixed material to a corundum crucible and place it in a box-type atmosphere sintering furnace for the first sintering. The sintering atmosphere is an oxygen-nitrogen mixture with an oxygen volume concentration of 30% and a gas flow rate of 15 L / min. The temperature is raised to 920 °C at a rate of 5 °C / min and held at this temperature for 12 hours, and then cooled to room temperature at the same rate.

[0029] (4) After the block material after one sintering is mechanically crushed, it is passed through a 400-mesh sieve to obtain sintered powder.

[0030] (5) The above sintered powder and the coating agent alumina (Al2O3) are mixed in a high-efficiency coating machine. The amount of Al2O3 added accounts for 0.8% of the mass of the sintered powder. After the mixture is uniform, the material is put back into the crucible.

[0031] (6) The material is sintered a second time. Sintering is carried out in an air atmosphere (flow rate 10 L / min), the temperature is raised to 650 °C at a rate of 10 °C / min, held for 6 hours, and then cooled naturally.

[0032] (7) After the material after secondary sintering is slightly crushed, it is passed through a 400-mesh sieve to finally obtain a single crystal cathode material with a median particle size D50 of 4.5 μm.

[0033] Example 2 : This embodiment provides a chemical formula Na 0.8 Fe 0.3 Mn 0.7 The specific steps for preparing single-crystal O2 cathode materials are as follows: (1) Weigh the iron-manganese binary precursor Fe precisely according to the target stoichiometric ratio. 0.3 Mn 0.7 (OH)₂ (D50 = 6.0 μm) and sodium hydroxide (NaOH) were mixed, with the total molar ratio of sodium (Na) to transition metal (Fe+Mn) controlled at 1:0.8. Simultaneously, ammonium molybdate flux (0.3% of the total mass of the precursor and sodium source), titanium oxide (TiO₂) lattice dopant (0.5% of the total mass of the precursor and sodium source), and zinc oxide (ZnO) (1.0%) were added.

[0034] (2) Place all the above raw materials in a high-speed mixer and dry mix at 1000 rpm for 1.5 hours to ensure that the mixture is uniform.

[0035] (3) The uniformly mixed materials are sintered for the first time. The sintering atmosphere is pure oxygen with a flow rate of 20 L / min. The temperature is increased to 950 °C at a rate of 8 °C / min and held at this temperature for 8 hours, and then cooled to room temperature at a rate of 3 °C / min.

[0036] (4) The material after one sintering is crushed and passed through a 400-mesh sieve to obtain sintered powder.

[0037] (5) The above sintered powder is mixed with the coating agent aluminum phosphate (AlPO4), and the amount of AlPO4 added accounts for 1.2% of the mass of the sintered powder.

[0038] (6) The material is sintered a second time. Sintering is carried out in a mixed atmosphere with an oxygen volume concentration of 40%, the temperature is raised to 700 °C at a rate of 5 °C / min, held for 5 hours, and then cooled naturally.

[0039] (7) The material after secondary sintering is sieved to finally obtain a single crystal cathode material with a median particle size D50 of 6.5 μm.

[0040] Example 3 : This embodiment provides a chemical formula Na 0.7 Fe 0.7 Mn 0.3 The specific steps for preparing single-crystal O2 cathode materials are as follows: (1) Weigh the iron-manganese binary precursor Fe precisely according to the target stoichiometric ratio. 0.7 Mn 0.3 CO3 (D50 = 3.5 μm) and sodium carbonate (Na2CO3) were used as the sodium source, with the total molar ratio of sodium (Na) to transition metal (Fe+Mn) controlled at 1:0.7. Simultaneously, a flux (composed of 0.2% B2O3 and 0.2% ammonium dihydrogen phosphate) accounting for 0.4% of the total mass of the precursor and sodium source, and a lattice dopant aluminum oxide (Al2O3) accounting for 1.5% of the total mass of the precursor and sodium source, were added.

[0041] (2) Place all the above raw materials in a high-speed mixer and dry mix at 700 rpm for 3 hours to ensure that the mixture is uniform.

[0042] (3) The uniformly mixed materials are sintered for the first time. The sintering atmosphere is air with a flow rate of 25 L / min. The temperature is increased to 880 °C at a rate of 10 °C / min and held at this temperature for 15 hours, and then cooled to room temperature at a rate of 5 °C / min.

[0043] (4) The material after one sintering is crushed and passed through a 500-mesh sieve to obtain sintered powder.

[0044] (5) The above sintered powder is mixed with the coating agent zirconium oxide (ZrO2), and the amount of ZrO2 added accounts for 0.3% of the mass of the sintered powder.

[0045] (6) The material is sintered a second time. Sintering is carried out in an air atmosphere, with the temperature increased to 550 °C at a rate of 8 °C / min, held for 8 hours, and then cooled naturally.

[0046] (7) The material after secondary sintering is sieved to finally obtain a single crystal cathode material with a median particle size D50 of 3.8 μm.

[0047] In the above embodiments, the iron-manganese binary precursor Fe x Mn 1-y (OH)2 or Fe x Mn 1-y CO3 is pre-prepared via a co-precipitation method. The sodium source, flux, dopant, and coating agent are all commercially available industrial-grade or battery-grade raw materials. The pulverization operation can be performed using a mortar and pestle, an air jet mill, or a mechanical pulverizer. The sieving operation aims to control the particle size distribution of the final product, ensuring its D50 falls within the range of 3.0-8.0 μm to meet the requirements of battery electrode processing. By adjusting the temperature, time, and atmosphere of the two sintering processes, the crystallinity, sodium content, and surface chemical environment of the single crystals can be effectively controlled, thereby obtaining a cathode material with excellent electrochemical performance.

[0048] Comparative Example 1 : This comparative example aims to illustrate that, in the preparation process of the iron-manganese base layer oxide single crystal cathode material, neither flux nor lattice dopant will be added, which will have a significant adverse effect on the structure and electrochemical performance of the material.

[0049] Preparation method: This comparative example uses the same iron-manganese binary precursor Fe as in Example 1. 0.5 Mn 0.5 (OH)₂ (D50 = 4.0 μm) and sodium carbonate (Na₂CO₃) were used, with the total molar ratio of sodium (Na) to transition metal (Fe + Mn) controlled at 1:0.5. The difference was that no flux (such as boric acid) or lattice dopant (such as magnesium oxide) was added during the high-speed mixing step. All subsequent process parameters and conditions, including mixing, two sintering cycles (920°C / 12h, 650°C / 6h), coating (0.8% Al₂O₃), pulverization, and sieving, were completely consistent with those in Example 1.

[0050] Performance Comparison: Due to the lack of flux to promote ion diffusion and grain growth at high temperatures, the primary sintering process may be insufficient, leading to reduced crystallinity and impurity phase formation. Simultaneously, the lack of dopant to stabilize the crystal lattice will significantly decrease the material's structural stability. The resulting product may exhibit poor grain development, severe primary particle agglomeration, and intensified phase transitions during electrochemical cycling, resulting in lower capacity and poorer cycle life.

[0051] Comparative Example 2 : This comparative example aims to illustrate that even with the addition of flux, material properties still have defects if the stabilizing effect of lattice dopant is lacking.

[0052] Preparation method: This comparative example uses the same iron-manganese binary precursor Fe as in Example 1. 0.5 Mn 0.5 (OH)₂ (D50 = 4.0 μm) and sodium carbonate (Na₂CO₃) (molar ratio 1:0.5) and boric acid (H₃BO₃, added at 0.1% of total mass) as flux. The difference is that no lattice dopant (i.e., no magnesium oxide) is added during the high-speed mixing step. All subsequent process steps and parameters are exactly the same as in Example 1.

[0053] Comparison of effects: The addition of flux helps with sintering densification and grain growth, and the resulting material may have better crystallinity than Comparative Example 1. However, due to the lack of dopants such as magnesium ions pinning in the crystal lattice and suppressing metal ion migration and lattice oxygen loss during charge and discharge, the bulk structural stability of the material under long-term cycling is insufficient, especially its ability to suppress manganese ion dissolution and oxygen evolution is weak. It is expected that its cycling stability, especially its capacity retention at high voltage, will be significantly worse than that of the sample in Example 1.

[0054] Performance testing and comparison : To quantitatively illustrate the beneficial effects of the technical solution of the present invention, the following parallel tests were conducted on the cathode material products obtained in the above embodiments, Comparative Example 1, and Comparative Example 2: Residual alkali (surface free sodium) test: Weigh approximately 5.0 g of sample, dissolve in 40 mL of deionized water, sonicate for 2 minutes, filter, and dilute the filtrate to a 100 mL volumetric flask. Determine the total alkali content in the filtrate using an automatic potentiometric titrator (model: METTLERTOLEDO G20), and express the residual alkali content of the material as the mass fraction of Na2O or NaOH.

[0055] Electrochemical performance testing : Electrode preparation: The positive electrode material, conductive carbon black (Super P), and polyvinylidene fluoride (PVDF) binder were mixed in a mass ratio of 80:10:10, and an appropriate amount of N-methylpyrrolidone (NMP) solvent was added. The mixture was then stirred into a uniform slurry in a vacuum mixer. The slurry was coated onto an aluminum foil current collector, dried at 120 °C, rolled, and then punched into circular electrode sheets with a diameter of 14 mm.

[0056] Battery Assembly: CR2032 button cells were assembled using a sodium metal sheet as the counter electrode and glass fiber (GF / D) as the separator in an argon-protected glove box (H2O < 0.1 ppm, O2 < 0.1 ppm). The electrolyte was a 1 M NaPF6 solution of ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) (volume ratio 1:1:1).

[0057] Test conditions: All batteries were tested at 25 ± 1 °C. The first charge-discharge cycle was conducted at a rate of 0.1 C (set specific capacity 150 mA / g), with a voltage range of 2.5-4.0 V (vs. Na). + / Na). Subsequent cycle tests were conducted using a 0.5 C charge and 1 C discharge mode.

[0058] Table 1 As shown in Table 1, the sodium-ion battery iron-manganese-based layered oxide single-crystal cathode material prepared in Example 2 exhibits significant advantages in several key performance indicators. Specifically, the cathode sheet compaction density of the Example 2 sample reaches 3.40 g / cm³. 3 This indicates that its single crystal particles have good morphological consistency and high tap density, which is beneficial to improving the volumetric energy density of the battery. Its residual alkali (free sodium) content is only 0.711%, far lower than 6.148% of Comparative Example 1. This also shows that the synergistic effect of the flux (ammonium molybdate) and dopants (titanium oxide and zinc oxide) used in Example 2 effectively promotes the completion of the sintering reaction, significantly reduces the alkaline by-products on the material surface, thereby mitigating interfacial side reactions and improving the processing stability and electrochemical compatibility of the material.

[0059] In terms of electrochemical performance, the sample in Example 2 exhibited excellent specific capacity and cycle stability: its initial discharge specific capacity at 0.1C reached 157 mAh / g, and it maintained a high capacity of 121 mAh / g at 1C rate; after 50 cycles, the capacity retention remained at 74.27%. This result indicates that the high initial sintering temperature (950℃) combined with the lattice doping of titanium and zinc effectively stabilized the main structure of the material, suppressed the migration and phase transition of iron and manganese ions during cycling, and thus ensured excellent long-term cycling performance.

[0060] In contrast, the sample in Comparative Example 1, lacking any flux or dopant, exhibited an electrode compaction density of only 2.98 g / cm³ and a residual alkali content as high as 6.148%, indicating poor crystallinity and severe surface side reactions. Its 0.1C specific capacity was 138 mAh / g, while its 1C capacity was only 93 mAh / g, with a capacity retention rate as low as 60.22% after 50 cycles. This further confirms the significant disadvantages of samples lacking flux and doping control in terms of structural stability and sodium ion diffusion kinetics.

[0061] Furthermore, it can be clearly seen from the scanning electron microscope images that the sample of Example 2 (see Example 2) Figure 1 As shown, thanks to the addition of flux, it exhibits a well-dispersed, smooth, plate-like single-crystal morphology; while the comparative example 1 sample (see...) Figure 2 (As shown) Due to the lack of a synergistic melting effect, it forms a secondary spherical polycrystalline structure with complex interparticle interfaces, high residual alkali, and low compaction density, ultimately leading to a significant deterioration in its electrochemical performance. See also Figure 3 As shown, the electrode compaction density test revealed that Example 2 was 10-15% higher than that of Comparative Example 1. (See also...) Figure 4 As shown, the initial discharge specific capacity test revealed that Example 2 was also slightly better than Comparative Example 1. See also Figure 4 As shown, the cyclic capacity retention rate test revealed that Example 2 was also 14% higher than Comparative Example 1.

[0062] In summary, by optimizing the sintering process and using fluxes and multi-component dopants in a synergistic manner, this invention has successfully achieved an integrated improvement in material structure and performance, fully demonstrating the effectiveness and advancement of the method.

[0063] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for preparing a layered oxide cathode material for sodium-ion batteries, characterized in that, The main component of the cathode material has the general chemical formula Na. a Fe x Mn 1-y O2, where 0.30≤a≤0.80, 0.2≤x≤0.8, 0.2≤y≤0.8; The method includes the following steps: S1, the iron-manganese binary precursor Fe x Mn 1-y (OH)2 and sodium source compound were precisely weighed according to the molar ratio of each element in the general chemical formula, and flux and lattice dopant were added. Then, they were thoroughly mixed by dry mixing to obtain a dispersion mixture. S2: The dispersion mixture obtained in step S1 is sintered for the first time in an oxygen-rich atmosphere at a sintering temperature of 880~980℃ and a holding time of 8~15h. Then it is cooled, crushed, graded and sieved to obtain sintered powder. S3: After thoroughly mixing the sintered powder obtained in step S2 with the coating agent, the mixture is sintered for the second time in an oxygen-rich atmosphere at a temperature of 500~750℃ and a holding time of 4~8h. Then, the mixture is cooled, pulverized, graded, and sieved to obtain the layered oxide cathode material for sodium-ion batteries.

2. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S1, the sodium element and the total molar amount of transition metal elements are weighed precisely according to a ratio of 1:0.3~1.

0.

3. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S1, the sodium source is selected from one or more of sodium carbonate, sodium hydroxide, and sodium nitrate.

4. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S1, the flux is selected from one or more of boric acid, boron oxide, ammonium molybdate, ammonium dihydrogen phosphate, diamine hydrogen phosphate, barium oxide, calcium oxide, and tungsten oxide, and the total mass of the flux accounts for 0.01% to 1% of the total mass of the precursor and the sodium source.

5. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S1, the lattice dopant is selected from one or more of the oxides, carbonates, and hydroxides of magnesium, aluminum, titanium, zinc, copper, aluminum, and lithium, and the total mass of the lattice dopant accounts for 0.1% to 7.0% of the total mass of the precursor and the sodium source.

6. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S2, the particle size of the powder sieved is within 400 mesh.

7. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S3, the coating agent is selected from one or more of alumina, aluminum phosphate, titanium dioxide, and zirconium oxide, and the total mass of the coating agent elements accounts for 0.1% to 1.5% of the total mass of the sintered powder obtained in step S2.

8. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In step S3, the median particle size D50 of the obtained sodium-ion battery layered oxide cathode material is controlled to be between 3.0 and 8.0 μm through grading and sieving.

9. The method for preparing the layered oxide cathode material for sodium-ion batteries according to claim 1, characterized in that, In steps S2 and S3, the oxygen-enriched atmosphere is pure oxygen or an oxygen-nitrogen mixture with an oxygen volume concentration of not less than 20%.

10. A method for preparing a sodium-ion battery layered oxide cathode material according to any one of claims 1 to 9, wherein the obtained sodium-ion battery layered oxide cathode material is...

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