Sodium ferric pyrophosphate positive electrode material as well as preparation method and application thereof

Abstract

The invention belongs to the technical field of battery positive electrode materials, and particularly relates to a ferric sodium pyrophosphate positive electrode material as well as a preparation method and application thereof. The preparation method of the ferric sodium pyrophosphate positive electrode material provided by the invention comprises the following steps: 1) dispersing ferric phosphate, a sodium source, phosphate and a reducing agent in water, carrying out spray granulation to form spray powder, and then carrying out airflow pulverization to obtain precursor particles with the D50 particle size of 2.0-6.0 [mu] m; 2) mixing the precursor particles obtained in the step 1) with ammonium oxalate, and then performing first calcination to obtain a first calcined material; and (3) mixing the primary calcined material obtained in the step (2) with silicon oxide, and performing secondary calcination and crushing to obtain the ferric sodium pyrophosphate positive electrode material. The preparation method provided by the invention improves the compaction density of the sodium phosphate pyrophosphate positive electrode material, and is suitable for large-scale production of sodium ion batteries with high volume energy density.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of battery positive electrode materials, and particularly relates to a sodium iron pyrophosphite phosphate positive electrode material and a preparation method and application thereof. BACKGROUND

[0002] Sodium-ion batteries have a wide application prospect due to their cost advantage. The working principle of sodium-ion batteries is similar to that of lithium-ion batteries, and energy storage and release are realized by reversible embedding and de-embedding of sodium ions between the positive and negative electrodes. At present, the positive electrode materials for sodium-ion batteries mainly include three categories: transition metal oxide systems, polyanion compounds (phosphate systems, fluorophosphate systems, sodium superionic conductor structures, etc.), and Prussian blue systems. Among them, sodium iron pyrophosphite phosphate positive electrode materials have attracted widespread attention and research, but the traditional solid-phase method for synthesizing such positive electrode materials has the problems of porous and blocky morphology, resulting in a low tap density of the sodium iron pyrophosphite phosphate positive electrode material of only 2.0-2.1 g / cm 3 , which limits its application in high-volume energy density scenarios. SUMMARY

[0003] Therefore, the technical problem to be solved by the present application is to overcome the defects of the traditional solid-phase method for synthesizing sodium iron pyrophosphite phosphate positive electrode materials, such as low tap density, which limits its application in high-volume energy density scenarios, so as to provide a sodium iron pyrophosphite phosphate positive electrode material and a preparation method and application thereof.

[0004] The present application provides a preparation method of a sodium iron pyrophosphite phosphate positive electrode material, comprising the following steps: 1) dispersing iron phosphate, a sodium source, a phosphate, and a reducing agent in water, forming a spray powder by spray granulation, and then performing airflow crushing to obtain precursor particles with a D50 particle size of 2.0-6.0 pm; 2) mixing the precursor particles obtained in step 1) with ammonium oxalate, and then performing first calcination to obtain a calcined material; 3) mixing the calcined material obtained in step 2) with silicon oxide, performing second calcination, and crushing to obtain the sodium iron pyrophosphite phosphate positive electrode material.

[0005] Preferably, the reducing agent in step 1) is at least one selected from citric acid, glucose, and carotene; The sodium source is at least one selected from sodium oxalate and sodium carbonate; The phosphate is at least one selected from disodium hydrogen phosphate and sodium dihydrogen phosphate; The mass ratio of the iron phosphate, the sodium source, the phosphate, and the reducing agent is (2.5-5):(1.5-3):(1-2):(1.5-4).

[0006] Optionally, the step of dispersing the iron phosphate, sodium source, phosphate, and reducing agent in water further comprises a step of sand milling the iron phosphate, which can promote the full fusion of raw materials.

[0007] Preferably, the iron phosphate, sodium source, phosphate, and reducing agent are mixed and dispersed in water in step 1) to form a slurry with a solid content of 20-40%. The solid content of the slurry refers to the total mass concentration of other substances in the slurry excluding water.

[0008] The spray granulation in step 1) is performed using a centrifugal spray dryer, and the inlet temperature of the centrifugal spray dryer is 180-250℃, and the rotation speed of the atomization disc of the centrifugal spray dryer is 8000-12000rpm.

[0009] Preferably, the D50 particle size of the spray granulation in step 1) is 6-12μm. The air pressure during the jet milling in step 1) is 0.5-1MPa, the frequency of the classification wheel is 100-140Hz, and the frequency of the air blower is 40-60Hz.

[0010] Preferably, the mass ratio of the precursor particles to ammonium oxalate in step 2) is 100:(1-2). The particle size of the ammonium oxalate ranges from 0.1-1.0μm. The rotation speed of the mixing in step 2) is 1400-1600rpm, and the mixing time is 20-40min.

[0011] The use of ammonium oxalate with a specific particle size range of 0.1-1.0μm and a specific mixing speed can form nano-sized ammonium oxalate particles, which further assist in improving the compaction density of the sodium iron pyrophosphate positive electrode material.

[0012] Preferably, the first calcination temperature in step 2) is 280-320℃, and the first calcination time is 5-7h.

[0013] Preferably, the mass ratio of the calcined material to silicon oxide in step 3) is 100:(0.3-0.8). The particle size of the silicon oxide ranges from 0.1-1.0μm. The rotation speed of the mixing in step 3) is 1400-1600rpm, and the mixing time is 25-35min.

[0014] Optionally, the silicon oxide includes at least one of silicon monoxide and silicon dioxide.

[0015] The application uses the silica with a specific particle size range of 0.1-1.0 μm to form nano-sized silica particles when mixed at a specific mixing speed, thereby further assisting in improving the tap density of the sodium iron phosphate pyrophosphate positive electrode material.

[0016] Preferably, the second calcination temperature in step 3) is 550-600 DEG C, and the second calcination time is 10-14 h.

[0017] Preferably, the crushing in step 3) is to a D50 particle size of 3.0-8.0 μm.

[0018] The application provides a sodium iron phosphate pyrophosphate positive electrode material prepared by the preparation method of the sodium iron phosphate pyrophosphate positive electrode material.

[0019] The application also provides a use of the sodium iron phosphate pyrophosphate positive electrode material in a sodium ion battery. The preparation method of the sodium iron phosphate pyrophosphate positive electrode material provided by the application comprises the following steps: 1) dispersing iron phosphate, a sodium source, a phosphate, and a reducing agent in water, forming spray powder through spray granulation, and then performing airflow crushing to obtain precursor particles with a D50 particle size of 2.0-6.0 μm; 2) mixing the precursor particles obtained in step 1) with ammonium oxalate, and then performing first calcination to obtain a calcined material; and 3) mixing the calcined material obtained in step 2) with silica, performing second calcination and crushing to obtain the sodium iron phosphate pyrophosphate positive electrode material. The spray material formed through spray granulation in the application is mostly a hollow shell with a thin shell layer and light material. After subsequent airflow crushing, the shell is broken, the material volume shrinks, irregularly shaped particles are obtained, the loose bulk density increases, and the crystal formation barrier is reduced during sintering, which is helpful for synthesizing tap density materials. Ammonium oxalate is preferentially decomposed when heated to release ammonia and carbon dioxide, which can timely remove the gas generated during the decomposition of sodium oxalate and organic matter, reduce the volume expansion of the main reaction material, and thus improve the material density. The high surface energy of the silica induces the spheroidization of the precursor, improves the flowability, strengthens the particle connection points, and thus improves the material density. The spray granulation, airflow crushing, mixing with ammonium oxalate for calcination, mixing with silica for calcination, and subsequent crushing in the application improve the material interface stress through the overall process cooperation, and thus improve the material density. The preparation method provided by the application improves the tap density of the sodium iron phosphate pyrophosphate positive electrode material, and is suitable for the large-scale production of sodium ion batteries with high volume energy density. BRIEF DESCRIPTION OF DRAWINGS

[0020] In order to more clearly illustrate the technical solutions in the specific embodiments of the present application or the prior art, the accompanying drawings required to be used in the specific embodiments or prior art description will be briefly introduced. Obviously, the accompanying drawings in the following description are some embodiments of the present application, and other drawings can be obtained by those skilled in the art without any creative effort on the premise that the accompanying drawings are not limited to the best mode of the present application.

[0021] Figure 1 SEM image of the sodium iron phosphate pyrophosphate positive electrode material prepared in Example 1 of the present application. DETAILED DESCRIPTION

[0022] The following examples are provided to better further understand the present application and are not limited to the best mode, and do not limit the content and scope of protection of the present application. Any person under the inspiration of the present application or the combination of the present application with other prior art features can obtain any product same or similar to the present application, which falls within the scope of protection of the present application.

[0023] The specific experimental steps or conditions are not indicated in the examples, which can be operated according to the conventional experimental steps described in the literature or the conditions. The reagents or instruments used are not indicated by the manufacturer, which are conventional reagent products that can be obtained by market purchase.

[0024] The sand-milled FePO4 used in the examples and comparative examples of the present application is FePO4 treated by sand milling, and the particle size range is 50-100 nm.

[0025] Example 1 The present embodiment provides a preparation method of a sodium iron phosphate pyrophosphate positive electrode material, which comprises the following steps: 1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4 and 946 g of citric acid (C6H8O7·H2O) were uniformly dispersed in 7620 g of pure water, and a D50 particle size of 10 μm of spherical powder was obtained by spray granulation (using a centrifugal spray dryer, inlet temperature 190℃, atomizing disc rotation speed 10000 rpm), and then air flow crushing (air pressure 0.6 MPa, classification wheel frequency 120 Hz, induced fan frequency 50 Hz) was carried out to obtain a D50 particle size of 2.0 μm of irregularly shaped precursor particles; 2) The precursor particles obtained in step 1) were mixed with ammonium oxalate (D50 particle size 0.5 μm) in a mass ratio of 100:1 in a high-speed mixer at a rotation speed of 1500 rpm for 30 min, and then calcined at 300℃ for 6 h to obtain a calcined material; 3) Put the calcined material obtained in step 2) and silicon dioxide (D50 particle size is 0.5 μm) in a mass ratio of 100:0.5 into a high-speed mixer and mix at a speed of 1500 rpm for 30 min, then calcine at 550 ℃ for 12 h, and then air-jet mill to a D50 particle size of 3.0 μm (air pressure is 0.6 MPa, classification wheel frequency is 120 Hz, and air blower frequency is 50 Hz), to obtain the sodium iron phosphate pyrophosphate positive electrode material. The obtained sodium iron phosphate pyrophosphate positive electrode material is scanned by a scanning electron microscope, and the SEM image of the sodium iron phosphate pyrophosphate positive electrode material is as shown in FIG. 2. Figure 1

[0026] Example 2 The embodiment provides a preparation method of a sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps: Put 1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4, and 946 g of citric acid (C6H8O7·H2O) into 8000 g of pure water, and obtain spherical powder with a D50 particle size of 6 μm by spray granulation (using a centrifugal spray dryer, inlet temperature is 180 ℃, and atomizing disc speed is 12000 rpm), and then air-jet mill (air pressure is 0.6 MPa, classification wheel frequency is 120 Hz, and air blower frequency is 50 Hz) to obtain irregular precursor particles with a D50 particle size of 2.0 μm; 2) Put the precursor particles obtained in step 1) and ammonium oxalate (D50 particle size is 0.1 μm) in a mass ratio of 100:2 into a high-speed mixer and mix at a speed of 1600 rpm for 20 min, and then calcine at 320 ℃ for 5 h to obtain a calcined material; 3) Put the calcined material obtained in step 2) and silicon dioxide (D50 particle size is 0.5 μm) in a mass ratio of 100:0.8 into a high-speed mixer and mix at a speed of 1600 rpm for 20 min, and then calcine at 580 ℃ for 10 h, and then air-jet mill to a D50 particle size of 3.0 μm (air pressure is 0.6 MPa, classification wheel frequency is 120 Hz, and air blower frequency is 50 Hz), to obtain the sodium iron phosphate pyrophosphate positive electrode material.

[0027] Example 3 The embodiment provides a preparation method of a sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps: ​1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4, and 946 g of citric acid (C6H8O7·H2O) were uniformly dispersed in 7800 g of pure water, and a spherical powder with a D50 particle size of 12 μm was obtained by spray granulation (using a centrifugal spray dryer, an inlet temperature of 250°C, and a rotation speed of the atomizing disc of 8000 rpm), and then the spherical powder was subjected to air jet pulverization (an air pressure of 0.6 MPa, a classification wheel frequency of 120 Hz, and a frequency of an air blower of 50 Hz) to obtain precursor particles with an irregular shape and a D50 particle size of 2.0 μm; 2) The precursor particles obtained in step 1) were mixed with ammonium oxalate (D50 particle size of 0.5 μm) at a mass ratio of 100:1.5 in a high-speed mixer at a rotation speed of 1400 rpm for 40 min, and then calcined at 280°C for 7 h to obtain a calcined material; 3) The calcined material obtained in step 2) and silicon dioxide (D50 particle size of 0.5 μm) were mixed at a mass ratio of 100:0.3 in a high-speed mixer at a rotation speed of 1400 rpm for 40 min, and then calcined at 600°C for 10 h, and then subjected to air jet pulverization to obtain a phosphoferric sodium phosphate positive electrode material with a D50 particle size of 3.0 μm (an air pressure of 0.6 MPa, a classification wheel frequency of 120 Hz, and a frequency of an air blower of 50 Hz).

[0028] Comparative Example 1 The present comparative example provides a method for preparing a phosphoferric sodium phosphate positive electrode material, which comprises the following steps: 1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4, and 946 g of citric acid (C6H8O7·H2O) were uniformly dispersed in 7800 g of pure water, and a spherical powder with a D50 particle size of 12 μm was obtained by spray granulation (using a centrifugal spray dryer, an inlet temperature of 250°C, and a rotation speed of the atomizing disc of 8000 rpm), and then the spherical powder was subjected to air jet pulverization (an air pressure of 0.6 MPa, a classification wheel frequency of 120 Hz, and a frequency of an air blower of 50 Hz) to obtain precursor particles with an irregular shape and a D50 particle size of 2.0 μm; 2) The precursor particles obtained in step 1) were mixed with ammonium oxalate (D50 particle size of 0.5 μm) at a mass ratio of 100:1 in a high-speed mixer at a rotation speed of 1400 rpm for 40 min, and then calcined at 280°C for 7 h to obtain a calcined material; 3) The calcined material obtained in step 2) and silicon dioxide (D50 particle size of 0.5 μm) were mixed at a mass ratio of 100:0.5 in a high-speed mixer at a rotation speed of 1400 rpm for 40 min, and then calcined at 600°C for 10 h, and then subjected to air jet pulverization to obtain a phosphoferric sodium phosphate positive electrode material with a D50 particle size of 3.0 μm (an air pressure of 0.6 MPa, a classification wheel frequency of 120 Hz, and a frequency of an air blower of 50 Hz).

[0029] Comparative Example 2 The present comparative example provides a preparation method of a sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps: 1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4, and 946 g of citric acid (C6H8O7·H2O) were uniformly dispersed in 7620 g of pure water, and a spherical powder with a D50 particle size of 10 μm was obtained through spray granulation (using a centrifugal spray dryer, an inlet temperature of 190°C, and an atomizing disc rotating speed of 10000 rpm), and then airflow crushing was performed (air pressure of 0.6 MPa, classification wheel frequency of 120 Hz, and induced fan frequency of 50 Hz) to obtain irregular precursor particles with a D50 particle size of 2.0 μm; 2) The precursor particles obtained in step 1) were placed in a high-speed mixer and mixed at a rotating speed of 1500 rpm for 30 min, and then calcined at 300°C for 6 h to obtain a calcined material; 3) The calcined material obtained in step 2) and silicon dioxide (D50 particle size of 0.5 μm) were placed in a high-speed mixer at a mass ratio of 100:0.5 and mixed at a rotating speed of 1500 rpm for 30 min, and then calcined at 550°C for 12 h, and then airflow crushed to a D50 particle size of 3.0 μm (air pressure of 0.6 MPa, classification wheel frequency of 120 Hz, and induced fan frequency of 50 Hz) to obtain a sodium iron phosphate pyrophosphate positive electrode material.

[0030] Comparative Example 3 The present comparative example provides a preparation method of a sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps: 1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4, and 946 g of citric acid (C6H8O7·H2O) were uniformly dispersed in 7620 g of pure water, and a spherical powder with a D50 particle size of 10 μm was obtained through spray granulation (using a centrifugal spray dryer, an inlet temperature of 190°C, and an atomizing disc rotating speed of 10000 rpm), and then airflow crushing was performed (air pressure of 0.6 MPa, classification wheel frequency of 120 Hz, and induced fan frequency of 50 Hz) to obtain irregular precursor particles with a D50 particle size of 2.0 μm; 2) The precursor particles obtained in step 1) were placed in a high-speed mixer and mixed at a rotating speed of 1500 rpm for 30 min, and then calcined at 300°C for 6 h to obtain a calcined material; 3) Put the calcined material obtained in step 2) into a high-speed mixer and mix at a speed of 1500 rpm for 30 min, then calcine at 550 ℃ for 12 h, and then air-jet mill to a D50 particle size of 3.0 μm (air pressure 0.6 MPa, classification wheel frequency 120 Hz, and air blower frequency 50 Hz), to obtain the sodium iron phosphate pyrophosphate positive electrode material.

[0031] Comparative Example 4 The present comparative example provides a method for preparing a sodium iron phosphate pyrophosphate positive electrode material, comprising the following steps: Disperse 1350 g of sand-milled FePO4, 603 g of Na2C2O4, 356 g of NaH2PO4, and 946 g of citric acid (C6H8O7·H2O) uniformly in 7620 g of pure water, spray granulate (using a centrifugal spray dryer, inlet temperature 190 ℃, atomizing disc speed 10000 rpm) to obtain spherical powder with a D50 particle size of 10 μm, and then air-jet mill (air pressure 0.6 MPa, classification wheel frequency 120 Hz, and air blower frequency 50 Hz) to obtain irregular precursor particles with a D50 particle size of 2.0 μm; 2) Put the precursor particles obtained in step 1) into a high-speed mixer and mix at a speed of 1500 rpm for 30 min, then calcine at 300 ℃ for 6 h to obtain a calcined material; 3) Put the calcined material obtained in step 2) into a high-speed mixer and mix at a speed of 1500 rpm for 30 min, then calcine at 550 ℃ for 12 h, and then air-jet mill to a D50 particle size of 3.0 μm (air pressure 0.6 MPa, classification wheel frequency 120 Hz, and air blower frequency 50 Hz), to obtain the sodium iron phosphate pyrophosphate positive electrode material.

[0032] Test Example The sodium iron phosphate pyrophosphate positive electrode materials prepared in Examples 1-3 and Comparative Examples 1-4 were respectively tested for the tap density, and the test method was in accordance with GB / T 44330-2024, and the test results are shown in Table 1.

[0033] The sodium iron phosphate pyrophosphate positive electrode material prepared in Examples 1-3 and Comparative Examples 1-4 was mixed with acetylene carbon black, PVDF at a mass ratio of 80:12:8, and 1-methyl-2 pyrrolidone was added to ball mill for 1 h to prepare a slurry, which was uniformly coated on an aluminum sheet, dried, cut into a positive electrode sheet, and assembled into a 2032 button cell with a metal sodium sheet as a negative electrode, a Celgard 2500 type separator as a separator, and a propylene carbonate (PC) solution containing 1 mol / L NaClO4 as an electrolyte. The above battery was tested for performance using a Land test system, and the test method was as follows: within the cut-off voltage of 2.0-3.8V, the first circle was charged and discharged at 0.1C, and then the 50th circle was charged and discharged at 1C, the first circle discharge specific capacity and 50th circle cycle capacity retention rate (i.e. the 51st circle discharge specific capacity / the 2nd circle discharge specific capacity x 100%) were tested, and the test results are shown in Table 1.

[0034] Table 1

[0035] As can be seen from Table 1, the tap density of the sodium iron phosphate pyrophosphate positive electrode material of Examples 1-3 of the present application is significantly better than that of Comparative Examples 1-4, which shows that the use of air flow crushing after spray granulation to form a spray material helps to improve the tap density of the positive electrode material, and the coating of sodium oxalate and the coating of silicon oxide material can synergistically improve the tap density of the positive electrode material, thereby being suitable for the large-scale production of sodium ion batteries with high volumetric energy density. At the same time, the first circle discharge specific capacity and 50th circle cycle retention rate of the sodium iron phosphate pyrophosphate positive electrode material of Examples 1-3 of the present application are basically similar to those of Comparative Examples 1-4, and even slightly better, which shows that the first circle discharge specific capacity and 50th circle cycle retention rate of the sodium iron phosphate pyrophosphate positive electrode material prepared by the present application are not affected.

[0036] Obviously, the above examples are merely examples for clarity and do not limit the embodiments. Based on the above description, other different forms of changes or variations can be made by those of ordinary skill in the art. Here, it is not necessary and impossible to exhaust all embodiments. The obvious changes or variations derived therefrom are still within the protection scope of the present application.

Claims

1. A method for preparing a sodium iron phosphate pyrophosphate positive electrode material, characterized in that, The method comprises the following steps: 1) dispersing iron phosphate, a sodium source, a phosphate, and a reducing agent in water, spray granulating to form a spray powder, and then performing air flow crushing to obtain precursor particles with a D50 particle size of 2.0-6.0 μm; 2) mixing the precursor particles obtained in step 1) with ammonium oxalate, and then performing first calcination to obtain a first-calcined material; 3) mixing the first-calcined material obtained in step 2) with silicon oxide, performing second calcination and crushing to obtain the sodium iron phosphate pyrophosphate positive electrode material.

2. The method of claim 1, wherein the sodium iron phosphate positive electrode material is prepared by the steps of: The reducing agent in step 1) is at least one selected from the group consisting of citric acid, glucose, and carotene; ​ The sodium source is at least one selected from the group consisting of sodium oxalate and sodium carbonate; The phosphate is at least one selected from the group consisting of disodium hydrogen phosphate and sodium dihydrogen phosphate; The mass ratio of the iron phosphate, the sodium source, the phosphate, and the reducing agent is (2.5-5):(1.5-3):(1-2):(1.5-4).

3. The method for preparing the sodium iron pyrophosphate cathode material according to claim 1, characterized in that, In step 1), the iron phosphate, the sodium source, the phosphate, and the reducing agent are mixed and dispersed in water to form a slurry with a solid content of 20-40%; In step 1), the spray granulation is performed using a centrifugal spray dryer, the inlet temperature of the centrifugal spray dryer is 180-250 ℃, and the rotation speed of the atomizing disc of the centrifugal spray dryer is 8000-12000 rpm.

4. The method for preparing the sodium iron pyrophosphate cathode material according to claim 1, characterized in that, In step 1), the D50 particle size of the spray granulation is 6-12 μm; In step 1), the air flow crushing is performed at an air pressure of 0.5-1 MPa, a classification wheel frequency of 100-140 Hz, and an air blower frequency of 40-60 Hz.

5. The method for preparing the sodium iron pyrophosphate cathode material according to claim 1, characterized in that, In step 2), the mass ratio of the precursor particles to ammonium oxalate is 100:(1-2); The particle size of the ammonium oxalate ranges from 0.1 μm to 1.0 μm; In step 2), the rotation speed of the mixing is 1400-1600 rpm, and the mixing time is 20-40 min.

6. The method of claim 1, wherein the sodium iron phosphate positive electrode material is prepared by the steps of: mixing a sodium source, an iron source, and a phosphate source; and heating the mixture to a temperature of 600-800°C for 1-10 hours in a non-oxidizing atmosphere. In step 2), the first calcination temperature is 280-320 ℃, and the first calcination time is 5-7 h.

7. The method for preparing the sodium iron pyrophosphate cathode material according to claim 1, characterized in that, In step 3), the mass ratio of the first-calcined material to silicon oxide is 100:(0.3-0.8); The particle size of the silicon oxide ranges from 0.1 μm to 1.0 μm; In step 3), the rotation speed of the mixing is 1400-1600 rpm, and the mixing time is 25-35 min.

8. The method for preparing the sodium iron pyrophosphate cathode material according to claim 1, characterized in that, In step 3), the second calcination temperature is 550-600 ℃, and the second calcination time is 10-14 h; and / or, in step 3), the crushing is performed to a D50 particle size of 3.0-8.0 μm.

9. A sodium iron phosphate pyrophosphate positive electrode material, characterized in that, The sodium iron phosphate pyrophosphate positive electrode material is prepared by the method described in any one of claims 1-8.

10. The sodium iron phosphate pyrophosphate positive electrode material of claim 9 for use in a sodium-ion battery.

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