A sodium-ion battery cathode material and a preparation method thereof

Abstract

The application relates to a sodium ion battery positive electrode material and a preparation method thereof, and belongs to the technical field of sodium ion batteries. The preparation method comprises the following steps: S1, uniformly mixing a first sodium source, a M 1 source, a M 2 source and a first iron source, and performing sintering to obtain a layered oxide; S2, uniformly mixing a second sodium source, a second iron source, a phosphorus source, an organic carbon source and a solvent, and grinding and spray drying to obtain a polyanion compound precursor; and S3, uniformly mixing the layered oxide, the polyanion compound precursor, sodium dihydrogen phosphate and diiron trioxide, and performing calcination to obtain the sodium ion battery positive electrode material. A "core-shell" composite structure design is adopted, the layered oxide is taken as the core to guarantee high specific capacity, the polyanion compound is taken as the shell to improve structural stability and cycle performance, and the synergistic optimization of "high specific capacity-high stability-high safety" is realized.

Description

Technical Field

[0001] This invention belongs to the field of sodium-ion battery technology, and particularly relates to a sodium-ion battery cathode material and its preparation method. Background Technology

[0002] With the growing global demand for sustainable development, the new energy industry has developed rapidly. Batteries, as crucial energy storage devices, directly impact the development of this industry through their performance and cost. Among various battery systems, lithium-ion batteries, with their high energy density and excellent cycle performance, are widely used in portable electronic devices, electric vehicles, and other fields. However, the limited availability and uneven distribution of lithium resources restricts their further development in large-scale energy storage. Against this backdrop, sodium-ion batteries, due to their abundant sodium resources, low cost, and the similar electrochemical insertion / extraction mechanisms of sodium and lithium ions, are widely recognized as an ideal complement and alternative to lithium-ion batteries, becoming a research hotspot in the field of new energy materials in recent years.

[0003] As a core component of sodium-ion batteries, the performance of cathode materials directly determines the battery's energy density, cycle stability, and safety. Currently, sodium-ion battery cathode materials are mainly classified into four types: Prussian blue-based, organic, layered oxide, and polyanionic. While Prussian blue-based materials have lower costs, they suffer from numerous crystal structure defects, high moisture sensitivity, and rapid capacity decay during cycling. Organic materials face challenges such as poor conductivity, insufficient oxidation stability, and difficulty in large-scale preparation. Layered oxide and polyanionic materials, due to their superior overall performance, have become the mainstream research and development direction and industrialization focus for sodium-ion battery cathode materials. Layered oxide materials exhibit high specific capacity, but their cycle stability, structural stability, and safety need improvement, specifically manifested in rapid capacity decay and high volume change rate during use. Polyanionic compounds, on the other hand, possess better cycle stability and structural stability, lower volume change rate, and higher safety, but their specific capacity is relatively lower.

[0004] In summary, existing sodium-ion battery cathode materials suffer from the core contradiction of "high specific capacity and high stability being mutually exclusive." Layered oxide materials have high specific capacity but insufficient stability, while polyanionic materials have excellent stability but low specific capacity. Neither can simultaneously meet the comprehensive requirements of large-scale energy storage for battery energy density, cycle life, and safety.

[0005] Therefore, developing a sodium-ion battery cathode material that combines the high specific capacity of layered oxides with the excellent cycle stability, structural stability, and safety of polyanionic materials, while also exhibiting a small volume change rate, is crucial for overcoming the industrialization bottleneck of sodium-ion batteries and has significant academic value and practical application implications. Summary of the Invention

[0006] To address the aforementioned technical problems, this invention provides a sodium-ion battery cathode material and its preparation method. It employs a "core-shell" composite structure design, using a layered oxide core to ensure high specific capacity and a polyanionic compound shell to enhance structural stability and cycle performance, achieving synergistic optimization of "high specific capacity, high stability, and high safety." Simultaneously, a stepwise sintering process is used, and sodium dihydrogen phosphate and ferric oxide are introduced as interface reinforcing agents during preparation. By filling interfacial voids, reducing interfacial lattice mismatch, and forming a transition layer, the interfacial compatibility problem caused by structural differences between the layered oxide and the polyanionic compound is effectively solved.

[0007] The first objective of this invention is to provide a method for preparing a sodium-ion battery cathode material, comprising the following steps: S1, the first sodium source, M 1 Source, M 2 The source and the first iron source are mixed evenly and then sintered to obtain a layered oxide. S2. The second sodium source, the second iron source, the phosphorus source, the organic carbon source and the solvent are mixed evenly, and then ground and spray dried to obtain the polyanionic compound precursor. S3. The layered oxide described in S1, the polyanionic compound precursor described in S2, sodium dihydrogen phosphate, and ferric oxide are mixed evenly and then calcined to obtain the sodium-ion battery cathode material.

[0008] In one embodiment of the present invention, in S1, the first sodium source is selected from one or more of sodium carbonate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, monosodium trihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium phosphate, sodium nitrate, sodium oxalate, sodium acetate, sodium sulfate, sodium hydroxide, sodium formate, and sodium citrate. And / or, the M 1 Source selected from M oxide 1 Hydroxide M 1 Carbonic acid M 1 fluoride M 1 M sulfuric acid 1 , Phosphate M 1 pyrophosphate M 1 and acetic acid M 1 One or more of the following; M 1 M in the source 1 Selected from one or more of nickel, manganese, vanadium, chromium, cobalt, copper, ruthenium, and iridium; And / or, the M 2 Source selected from M oxide 2 Hydroxide M 2 Carbonic acid M 2 Fluoride M 2 M sulfuric acid 2 , Phosphate M 2 pyrophosphate M2 and acetic acid M 2 One or more of the following; M 2 M in the source 2 Selected from one or more of titanium, magnesium, aluminum, calcium, zinc, strontium, zirconium, yttrium, tin, antimony, tungsten, barium, and niobium; And / or, the first iron source is selected from one or more of iron oxide, iron sulfate and iron phosphate.

[0009] In one embodiment of the present invention, in S1, the first sodium source, M 1 Source, M 2 The amounts of the first iron source and the second iron source satisfy the chemical formula Na. p M 1 x M 2 y Fe 1-x-y O2, 0.85≤p≤1.05.

[0010] In one embodiment of the present invention, in S1, the sintering is carried out in an air atmosphere or an oxygen atmosphere, with the temperature increased to 800°C-1000°C at a rate of 4.8°C / min-5.2°C / min, and held at that temperature for 8h-15h.

[0011] In one embodiment of the present invention, in S2, the second sodium is derived from one or more of sodium carbonate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, monosodium trihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium phosphate, sodium nitrate, sodium oxalate, sodium acetate, sodium sulfate, sodium hydroxide, sodium formate, and sodium citrate. And / or, the second iron source is selected from one or more of iron oxide, iron sulfate, and iron phosphate; And / or, the phosphorus source is selected from one or more of sodium dihydrogen phosphate, sodium phosphate, sodium monohydrogen phosphate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, pyrophosphate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, and trisodium monohydrogen pyrophosphate. And / or, the organic carbon source is selected from one or more of glucose, sucrose, polyethylene glycol, cyclodextrin, phenolic resin, ascorbic acid, formaldehyde, acetaldehyde, n-butyraldehyde, lactic acid, citric acid, malic acid, oxalic acid, adipic acid, soluble starch, and ethylenediaminetetraacetic acid; And / or, the solvent is selected from one or more of water, ethylenediamine, cyclohexane, acetone, methanol, ethanol, propanol, isopropanol, ethylene glycol and n-butanol.

[0012] In one embodiment of the present invention, in S2, the amounts of the second sodium source, the second iron source, and the phosphorus source satisfy the chemical formula Na m Fe n (PO4)2P2O7, 3.8≤m≤4.2, 2.8≤n≤3.2; And / or, the amount of the organic carbon source used is 1%-10% of the total mass of the second sodium source, the second iron source, the phosphorus source and the organic carbon source; And / or, the solid content of the second sodium source, second iron source, phosphorus source, and organic carbon source after being dispersed in water is 10%-40%.

[0013] In one embodiment of the present invention, in S2, the grinding is to grind the particle size of the solid particles in the slurry to below 500 nm; And / or, the process parameters of the spray drying are: inlet air temperature of 145℃-155℃, outlet air temperature of 70℃-80℃, pressure atomization with an atomization pressure of 0.3MPa-0.4MPa, a feed rate of 10mL / min-12mL / min, and a tower pressure of -0.04MPa to -0.02MPa.

[0014] In one embodiment of the present invention, in S3, the mass ratio of the layered oxide to the polyanionic compound precursor is (5-9):(1-5). And / or, the amount of sodium dihydrogen phosphate used is 8%-12% of the total mass of the layered oxide and polyanionic compound precursor; And / or, the amount of ferric oxide used is 1%-2% of the total mass of the layered oxide and the polyanionic compound precursor.

[0015] In one embodiment of the present invention, in S3, the calcination is carried out under an inert or reducing atmosphere, first by heating to 300℃-400℃ at a rate of 1.8℃ / min-2.2℃ / min and holding for 3h-6h. This helps to remove the water of crystallization and small molecule gases such as CO2 and H2O generated by the decomposition of organic carbon sources in the polyanionic compound precursor, avoiding particle cracking due to rapid degassing during subsequent high-temperature calcination. On the other hand, it promotes the full melting of sodium dihydrogen phosphate, thereby effectively filling the interfacial gaps between the layered oxide and the polyanionic compound precursor. Then, the temperature is raised to 500℃-550℃ at a rate of 2.8℃ / min-3.2℃ / min and held for 10h-14h to form the surface polyanionic crystalline phase.

[0016] A second objective of this invention is to provide a sodium-ion battery cathode material prepared by the method described above.

[0017] The technical solution of the present invention has the following advantages compared with the prior art: (1) The preparation method of the present invention introduces sodium dihydrogen phosphate and ferric oxide as interface reinforcing agents. The two can effectively fill the micropores and gaps between the layered oxide core and the polyanionic compound shell, reduce the interfacial voids, and form a (Na, M1, M2, Fe)3(PO4)2 transition layer to reduce the interfacial lattice mismatch, thereby reducing the interfacial resistance, improving the ion transport efficiency, and enhancing the rate performance and cycle stability of the material; among them, sodium dihydrogen phosphate helps to supplement PO4 3- This promotes shell crystallization. Ferric oxide can synergistically interact with the transition metals in the layered oxide core and Fe in the polyanionic shell, driving the formation of the (Na, M1, M2, Fe)3(PO4)2 transition layer to further optimize lattice matching. This transition layer is an amorphous mixed phase overall, containing Na... + Uniformly distributed and acting as charge-compensating ions, they fill the interstices of the metal-oxygen / phosphorus-oxygen polyhedra to ensure interfacial charge neutrality. The side closest to the core layer is characterized by the M-type of layered oxides. 1 / M 2 -O octahedron as the main body, with some O 2- by PO4 3- / P2O7 4- The group is substituted, and the concentration of this group gradually decreases from the core to the shell. Near the shell, the Fe-PO polyhedron, a polyanionic compound, is predominantly present, with some Fe... 2+ / Fe 3+ M 1 / M 2 Replace and M 1 / M 2 The concentration gradually decreases from the shell to the core.

[0018] (2) The sodium-ion battery cathode material of the present invention has excellent specific capacity, cycle stability and structural stability, which is due to its core-shell composite structure design: with layered oxide as the core, it gives full play to its inherent advantage of high specific capacity; with polyanionic compound as the shell, which contains PO4 3- P2O7 4- The functional groups can effectively support and stabilize the crystal structure of the material, preventing structural collapse. Furthermore, the polyanionic compound exhibits small volume changes and minimal phase transitions during sodium ion insertion and extraction, further ensuring the structural stability and safety of the material. Simultaneously, the shell can effectively isolate the layered oxide from direct contact with the electrolyte, suppressing interfacial side reactions. Its strong PO bonding network can also effectively prevent the dissolution of transition metals, thereby significantly extending the cycle life of the layered oxide. Attached Figure Description

[0019] To make the content of this invention easier to understand, the invention will be further described in detail below with reference to specific embodiments and accompanying drawings, wherein: Figure 1 The discharge curve of the button cell in Test Example 1 of the present invention is shown. Figure 2 This is a cycle curve diagram of the button cell of Test Example 1 of the present invention. Detailed Implementation

[0020] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. It should be understood that the specific embodiments are only used to explain the present invention, but the embodiments are not intended to limit the present invention.

[0021] In this invention, unless otherwise stated, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0022] In this invention, unless otherwise stated, the term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0023] In this invention, unless otherwise specified, the experimental methods used in the embodiments of this invention are conventional methods, and the materials and reagents used are commercially available unless otherwise specified. Example 1

[0024] The sodium-ion battery cathode material and its preparation method in this embodiment specifically include the following steps: S1. Preparation of layered oxides: Using sodium carbonate as the sodium source, nickel oxide as the nickel source, ferric oxide as the iron source, and manganese dioxide as the manganese source, according to NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 After the stoichiometric ratio of O2 is fully mixed, the resulting material is placed in an air atmosphere and heated to 1000℃ at a rate of 5℃ / min and held for 8 hours to obtain layered oxides. S2. Preparation of polyanionic compound precursor: Sodium carbonate as sodium source, iron phosphate as iron and phosphorus source, sodium dihydrogen phosphate as sodium and phosphorus source, and glucose as organic carbon source (5% of the total mass of sodium, iron, and phosphorus sources) were thoroughly mixed according to the stoichiometric ratio of Na4Fe3(PO4)2P2O7. Water was added at a solid content of 40%, and the mixture was ground and mixed using a sand mill to control the particle size of the slurry to 300 nm. Subsequently, spray drying was performed, with the inlet air temperature controlled at 150℃ and the outlet air temperature at 75℃. Pressure atomization was used with an atomization pressure of 0.35 MPa, a feed rate of 11 mL / min, and a tower pressure of -0.03 MPa to obtain the polyanionic compound precursor. S3. Preparation of sodium-ion battery cathode material: Layered oxide and polyanionic compound precursors were weighed at a mass ratio of 9:1. Sodium dihydrogen phosphate dihydrate and ferric oxide were added at 8% of the total mass of the layered oxide and polyanionic compound precursors, and ferric oxide at 1%. All materials were thoroughly mixed. The mixture was then heated to 350℃ at a rate of 2℃ / min and held for 3 hours in a nitrogen atmosphere. The temperature was then increased to 500℃ at a rate of 3℃ / min and held for 12 hours to obtain NaNi... 1 / 3 Fe 1 / 3 Mn 1 / 3 A sodium-ion battery cathode material with O2 as the core and Na4Fe3(PO4)2P2O7 as the shell, namely (Na1Ni 1 / 3 Fe 1 / 3 Mn 1 / 3 O2@Na4Fe3(PO4)2P2O7). Comparative Example 1

[0025] It is basically the same as Example 1, except that it only contains layered oxides. Example 2

[0026] The sodium-ion battery cathode material and its preparation method in this embodiment specifically include the following steps: S1. Preparation of layered oxides: Using sodium carbonate as the sodium source, nickel oxide as the nickel source, ferric oxide as the iron source, manganese dioxide as the manganese source, and titanium dioxide as the titanium source, according to Na... 0.85 Ni 1 / 3 Fe 1 / 3 Mn 3 / 12 Ti 1 / 12 After the stoichiometric ratio of O2 is fully mixed, the resulting material is placed in an air atmosphere and heated to 900℃ at a rate of 5℃ / min and held for 10h to obtain layered oxides. S2. Preparation of polyanionic compound precursor: Sodium carbonate as sodium source, iron phosphate as iron and phosphorus source, sodium dihydrogen phosphate as sodium and phosphorus source, and citric acid as organic carbon source (5% of the total mass of sodium, iron, and phosphorus sources) were thoroughly mixed according to the stoichiometric ratio of Na4Fe3(PO4)2P2O7. Water was added at a solid content of 30%, and the mixture was ground and mixed using a sand mill to control the particle size of the slurry to 400 nm. Subsequently, spray drying was carried out, with the inlet air temperature controlled at 150℃ and the outlet air temperature at 75℃. Pressure atomization was used with an atomization pressure of 0.35 MPa, a feed rate of 11 mL / min, and an internal pressure of -0.03 MPa to obtain the polyanionic compound precursor. S3. Preparation of sodium-ion battery cathode material: Layered oxide and polyanionic compound precursors were weighed at a mass ratio of 5:5. Sodium dihydrogen phosphate dihydrate and ferric oxide were added at 12% of the total mass of the layered oxide and polyanionic compound precursors and 2% of the total mass of the precursors. After thoroughly mixing all materials, the mixture was heated to 350℃ at a rate of 2℃ / min and held for 6 hours in a nitrogen atmosphere. Then, the temperature was increased to 550℃ at a rate of 3℃ / min and held for 12 hours to obtain the cathode material for sodium-ion batteries. 0.85 Ni 1 / 3 Fe 1 / 3 Mn 3 / 12 Ti 1 / 12 A sodium-ion battery cathode material with O2 as the core and Na4Fe3(PO4)2P2O7 as the shell, i.e. (Na 0.85 Ni 1 / 3 Fe 1 / 3 Mn 3 / 12 Ti 1 / 12 O2@Na4Fe3(PO4)2P2O7). Comparative Example 2

[0027] The process is basically the same as in Example 2, except that only polyanionic compounds are used, which are prepared according to S2 and then sintered using the process in S3. Comparative Example 3

[0028] The process is basically the same as in Example 2, except that sodium dihydrogen phosphate dihydrate and ferric oxide are not introduced in S3. Comparative Example 4

[0029] The process is basically the same as in Example 2, except that ferric oxide is not introduced in S3. Comparative Example 5

[0030] The process is basically the same as in Example 2, except that sodium dihydrogen phosphate dihydrate is not introduced in S3. Test Example 1

[0031] The sodium-ion battery cathode material prepared in the examples and comparative examples was used to make a coin cell. The specific steps included: the sodium-ion battery cathode material, conductive agent Super P, and binder PVDF were mixed in a mass ratio of 8:1:1, and N-methylpyrrolidone (NMP) was added to make a uniform slurry. The slurry was uniformly coated on the surface of aluminum foil, and after vacuum drying at 120°C for 12 hours, it was stamped to form a cathode sheet. Using metallic sodium as the counter electrode, glass fiber as the separator, and 1 mol / L NaPF6-EC / DMC (volume ratio 1:1) as the electrolyte, a CR2032 type coin cell was assembled in an argon glove box.

[0032] (1) Charge-discharge specific capacity: In a constant temperature chamber at 25℃, first charge at a constant current of 0.1C to 4.0V, then charge at a constant voltage of 4.0V until the current is less than 0.02C and stop, then discharge at a constant current of 0.1C to 2.0V, and record the charge specific capacity, discharge specific capacity and efficiency of this cycle; (2) Cyclic stability: In a constant temperature chamber at 25℃, the test conditions are 1.0C rate and voltage range of 2.0V-4.0V. The battery is subjected to 50 cycles of charge and discharge test. The charge and discharge process of each cycle refers to the charge and discharge operation of the corresponding rate (constant current charging to 4.0V, then constant voltage charging to the current less than 0.02C, and then constant current discharging to 2.0V). The capacity retention rate after 50 cycles is calculated by recording the change of the battery's discharge specific capacity during the cycle. (3) Rate performance: In a constant temperature chamber at 25℃, charge and discharge tests were conducted sequentially at rates of 0.2C, 0.5C, 1C, 2C, 5C, and 10C. The charge and discharge process for each cycle was based on the corresponding rate (constant current charging to 4.0V followed by constant voltage charging to a current less than 0.02C, and then constant current discharging to 2.0V). The capacity retention rate at 10C rate was calculated by recording the change in the specific capacity of the battery at different rates. Figures 1-2 The relevant performance results are shown in Table 1. Table 1

[0033] from Figures 1-2 As can be seen from Table 1, the first discharge specific capacity of the embodiments is at a high level, the 1C cycle retention rate is over 98%, the 10C rate capacity retention rate is significantly better than the comparative embodiment, and it has both high specific capacity and high stability, as well as better structural integrity and ion transport efficiency.

[0034] Comparing Example 1 and Comparative Example 1, it can be seen that the initial discharge specific capacity of Example 1 is slightly lower than that of Comparative Example 1, which only contains layered oxides, but the 1C cycle retention rate and 10C capacity retention rate are significantly improved. This indicates that although the polyanion shell has a slight impact on the initial specific capacity, it can effectively suppress the structural decay of layered oxides and significantly improve cycle stability and rate performance.

[0035] Comparing Example 2 and Comparative Example 2, it can be seen that Example 2 comprehensively surpasses Comparative Example 2, which contains only polyanionic compounds, in terms of initial discharge specific capacity, 1C cycle retention rate, and 10C capacity retention rate. This demonstrates the synergistic effect of the high specific capacity advantage of the layered oxide core and the stability advantage of the polyanionic shell, resolving the contradiction that "high capacity and high stability cannot be simultaneously achieved" in a single material.

[0036] Comparing Example 2 and Comparative Example 3, it can be seen that their initial discharge specific capacities are similar, but their 1C cycle retention and 10C capacity retention differ significantly. This indicates that the interface reinforcing agent composed of sodium dihydrogen phosphate and ferric oxide can effectively fill the voids at the core-shell interface, reduce lattice mismatch, improve interfacial compatibility, and thus enhance the cycling stability and rate performance of the material.

[0037] Comparing Example 2 and Comparative Example 4, it can be seen that Comparative Example 4, which lacks ferric oxide, has lower 1C cycle retention and 10C capacity retention than Example 2. This indicates that ferric oxide can synergistically interact with the core transition metal and shell Fe to promote (Na, M 1 M 2 The Fe)3(PO4)2 transition layer is formed, which optimizes the lattice matching degree and enhances the interfacial bonding force.

[0038] Comparing Example 2 and Comparative Example 5, it can be seen that Comparative Example 5, lacking sodium dihydrogen phosphate, not only has a lower initial discharge specific capacity, but also significantly insufficient 1C cycle retention and 10C capacity retention. This indicates that sodium dihydrogen phosphate can supplement PO42-. 3- It promotes shell crystallization and can melt and fill interfacial voids, reducing interfacial resistance and ensuring the specific capacity and ion transport efficiency of the material.

[0039] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A method for preparing a sodium-ion battery cathode material, characterized in that, Includes the following steps: S1, the first sodium source, M 1 Source, M 2 The source and the first iron source are mixed evenly and then sintered to obtain a layered oxide. S2. The second sodium source, the second iron source, the phosphorus source, the organic carbon source and the solvent are mixed evenly, and then ground and spray dried to obtain the polyanionic compound precursor. S3. The layered oxide described in S1, the polyanionic compound precursor described in S2, sodium dihydrogen phosphate, and ferric oxide are mixed evenly and then calcined to obtain the sodium-ion battery cathode material.

2. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S1, the first sodium source is selected from one or more of sodium carbonate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, monosodium trihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium phosphate, sodium nitrate, sodium oxalate, sodium acetate, sodium sulfate, sodium hydroxide, sodium formate, and sodium citrate. And / or, the M 1 Source selected from M oxide 1 Hydroxide M 1 Carbonic acid M 1 Fluoride M 1 M sulfuric acid 1 , Phosphate M 1 pyrophosphate M 1 and acetic acid M 1 One or more of the following; M 1 M in the source 1 Selected from one or more of nickel, manganese, vanadium, chromium, cobalt, copper, ruthenium, and iridium; And / or, the M 2 Source selected from M oxide 2 Hydroxide M 2 Carbonic acid M 2 Fluoride M 2 M sulfuric acid 2 , Phosphate M 2 pyrophosphate M 2 and acetic acid M 2 One or more of the following; M 2 M in the source 2 Selected from one or more of titanium, magnesium, aluminum, calcium, zinc, strontium, zirconium, yttrium, tin, antimony, tungsten, barium, and niobium; And / or, the first iron source is selected from one or more of iron oxide, iron sulfate, and iron phosphate.

3. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S1, the first sodium source, M 1 Source, M 2 The amounts of the first iron source and the second iron source satisfy the chemical formula Na. p M 1 x M 2 y Fe 1-x-y O2, 0.85≤p≤1.

05.

4. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S1, the sintering is carried out in an air atmosphere or an oxygen atmosphere, with the temperature increased to 800℃-1000℃ at a rate of 4.8℃ / min-5.2℃ / min, and held at that temperature for 8h-15h.

5. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S2, the second sodium is derived from one or more of sodium carbonate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, monosodium trihydrogen pyrophosphate, sodium dihydrogen phosphate, sodium phosphate, sodium nitrate, sodium oxalate, sodium acetate, sodium sulfate, sodium hydroxide, sodium formate, and sodium citrate. And / or, the second iron source is selected from one or more of iron oxide, iron sulfate, and iron phosphate; And / or, the phosphorus source is selected from one or more of sodium dihydrogen phosphate, sodium phosphate, sodium monohydrogen phosphate, phosphoric acid, ammonium dihydrogen phosphate, diammonium hydrogen phosphate, triammonium phosphate, pyrophosphate, sodium pyrophosphate, disodium dihydrogen pyrophosphate, and trisodium monohydrogen pyrophosphate. And / or, the organic carbon source is selected from one or more of glucose, sucrose, polyethylene glycol, cyclodextrin, phenolic resin, ascorbic acid, formaldehyde, acetaldehyde, n-butyraldehyde, lactic acid, citric acid, malic acid, oxalic acid, adipic acid, soluble starch, and ethylenediaminetetraacetic acid; And / or, the solvent is selected from one or more of water, ethylenediamine, cyclohexane, acetone, methanol, ethanol, propanol, isopropanol, ethylene glycol and n-butanol.

6. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S2, the amounts of the second sodium source, the second iron source, and the phosphorus source satisfy the chemical formula Na m Fe n (PO4)2P2O7, 3.8≤m≤4.2, 2.8≤n≤3.2; And / or, the amount of the organic carbon source used is 1%-10% of the total mass of the second sodium source, the second iron source, the phosphorus source and the organic carbon source; And / or, the solid content of the second sodium source, second iron source, phosphorus source, and organic carbon source after being dispersed in water is 10%-40%.

7. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S2, the grinding is to grind the particle size of the solid particles in the slurry to below 500 nm; And / or, the process parameters of the spray drying are: inlet air temperature of 145℃-155℃, outlet air temperature of 70℃-80℃, pressure atomization with an atomization pressure of 0.3MPa-0.4MPa, a feed rate of 10mL / min-12mL / min, and a tower pressure of -0.04MPa to -0.02MPa.

8. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S3, the mass ratio of the layered oxide to the polyanionic compound precursor is (5-9):(1-5). And / or, the amount of sodium dihydrogen phosphate used is 8%-12% of the total mass of the layered oxide and polyanionic compound precursor; And / or, the amount of ferric oxide used is 1%-2% of the total mass of the layered oxide and the polyanionic compound precursor.

9. The method for preparing the sodium-ion battery cathode material according to claim 1, characterized in that, In S3, the calcination is carried out under an inert or reducing atmosphere by first heating to 300℃-400℃ at a rate of 1.8℃ / min-2.2℃ / min and holding for 3h-6h, and then heating to 500℃-550℃ at a rate of 2.8℃ / min-3.2℃ / min and holding for 10h-14h.

10. The sodium-ion battery cathode material prepared by the method according to any one of claims 1-9.

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