High-compaction lithium iron phosphate positive electrode material and preparation method thereof

Abstract

The invention provides a high-compaction lithium iron phosphate positive electrode material and a preparation method thereof, and belongs to the field of recycling and repairing of lithium ion battery materials. The method comprises the following steps: step 1, dispersing iron phosphate, lithium carbonate, glucose, polyethylene glycol PEG and titanium dioxide into water to form first slurry; step 2, sanding the first slurry to a first predetermined particle size requirement, and then performing spray drying to obtain first solid powder; 3, roasting the first solid powder to obtain a sample A; step 4, dispersing iron phosphate, lithium carbonate, glucose and PEG into water to form second slurry; step 5, sanding the second slurry to a second predetermined particle size requirement, and then performing spray drying to obtain second solid powder; step 6, roasting the second solid powder to obtain a sample B; and step 7, mixing the sample A and the sample B, carrying out size mixing, carrying out sand milling, controlling to a third preset particle size requirement, carrying out spray drying, then carrying out roasting, and carrying out airflow crushing to obtain the high-compaction lithium iron phosphate positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of lithium-ion battery cathode materials, specifically to a high-pressure lithium iron phosphate cathode material and its preparation method. Background Technology

[0002] Lithium iron phosphate (LiFePO4) has become an indispensable key cathode material in the field of lithium-ion batteries due to its excellent safety, long cycle life, low cost, and environmental friendliness. It is mainly used in electric vehicles and energy storage systems.

[0003] High-compact lithium iron phosphate (LFP) is a key material technology in the fields of power batteries and energy storage. Its core objective is to fill more active material within a limited volume, thereby increasing the volumetric energy density of the battery. Therefore, in recent years, the new energy market has placed higher demands on the compaction density of LFP. Currently, the common synthesis route for LFP uses ferrous oxalate, monoammonium phosphate, or iron phosphate and lithium carbonate as raw materials, followed by sand milling and spraying, and then sintering. Due to the large release of gas, the resulting product has poor material density and generally exhibits low compaction. Therefore, there is an urgent need to develop a high-compact LFP material to meet market demands. Summary of the Invention

[0004] This invention is made to solve the above-mentioned problems, and its purpose is to provide a high-pressure lithium iron phosphate cathode material and its preparation method.

[0005] This invention provides a method for preparing a high-pressure lithium iron phosphate cathode material, characterized by the following steps: Step 1, dispersing iron phosphate, lithium carbonate, glucose, polyethylene glycol (PEG), and titanium dioxide in water according to a first predetermined ratio to form a first slurry; Step 2, milling the first slurry to a first predetermined particle size and then spray-drying it to obtain a first solid powder; Step 3, calcining the first solid powder to obtain sample A; Step 4, dispersing iron phosphate, lithium carbonate, glucose, and PEG in water according to a second predetermined ratio to form a second slurry; Step 5, milling the second slurry to a second predetermined particle size and then spray-drying it to obtain a second solid powder; Step 6, calcining the second solid powder to obtain sample B; Step 7, mixing sample A and sample B according to a third predetermined ratio to form a slurry, milling it to a third predetermined particle size and then spray-drying it to obtain a third solid powder; Step 8, calcining the third solid powder to obtain sample C; Step 9, pulverizing sample C to obtain the high-pressure lithium iron phosphate cathode material.

[0006] The method for preparing high-pressure lithium iron phosphate cathode material provided by this invention may also have the following characteristics: In step 1, the iron-phosphorus molar ratio of iron phosphate is 0.97-0.99:1, the lithium-iron molar ratio of lithium carbonate is 1.0-1.05:1, the mass addition of glucose is 6-10%, the mass addition of PEG is 1%-5%, and the mass addition of titanium dioxide is 0.2%-1%; In step 4, the iron-phosphorus molar ratio of iron phosphate is 0.95-0.97:1, the lithium-iron molar ratio of lithium carbonate is 1.0-1.05:1, the mass addition of glucose is 6-10%, and the mass addition of PEG is 1%-5%.

[0007] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following feature: in step 2, the first predetermined particle size requirement is D50 = 0.2-0.5 μm.

[0008] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following characteristics: in step 3, the heating rate of calcination is 2℃ / min-10℃ / min, the temperature is 500℃ / min-700℃, and the holding time is 2℃ / min-5h.

[0009] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following feature: in step 5, the second predetermined particle size requirement is D50 = 0.8 μm-1.3 μm.

[0010] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following characteristics: in step 6, the heating rate of calcination is 2℃ / min-10℃ / min, the temperature is 500℃-700℃, and the holding time is 2h-5h.

[0011] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following characteristics: in step 7, the mass ratio of sample A to sample B is 5:5-9:1, and the third predetermined particle size requirement is D50 = 0.4-0.6 μm.

[0012] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following characteristics: in step 8, the calcination heating rate is 2℃ / min-10℃ / min, the temperature is 750℃-850℃, and the holding time is 5h-15h.

[0013] The method for preparing high-pressure lithium iron phosphate cathode material provided by the present invention may also have the following characteristics: in step 9, the final product after air jet milling has a D50 of 0.8 μm-1.5 μm.

[0014] The present invention also provides a high-density lithium iron phosphate cathode material, characterized in that it is prepared by the above-mentioned high-density lithium iron phosphate cathode material preparation method.

[0015] Compared with existing lithium iron phosphate synthesis technologies, the advantages of this invention are:

[0016] This invention provides a method for preparing high-compact lithium iron phosphate cathode material. First, two primary particles with different particle sizes are prepared and sintered at low temperature. Then, the two particles are wet-mixed and graded. The mixed slurry is milled twice to control the particle size and then spray-dried. The sprayed material is sintered twice to obtain the finished product. The material prepared by this invention through two sintering processes has high crystallinity, more rounded particles, improved material density, and higher powder compaction density. Attached Figure Description

[0017] Figure 1 This is a scanning electron microscope image of the high-pressure lithium iron phosphate material in Embodiment 1 of the present invention;

[0018] Figure 2 This is a charge-discharge curve of the high-pressure lithium iron phosphate material in Embodiment 1 of the present invention. Detailed Implementation

[0019] To make the technical means, creative features, objectives and effects of this invention easy to understand, the following embodiments, in conjunction with the accompanying drawings, specifically illustrate the high-pressure lithium iron phosphate cathode material and its preparation method of this invention.

[0020] Example 1

[0021] This embodiment provides a high-pressure lithium iron phosphate cathode material and its preparation method, which includes the following steps:

[0022] Step 1: Select iron phosphate with a molar ratio of 0.98:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose, 2% polyethylene glycol (PEG), and 0.5% titanium dioxide by mass. Control the solid content to 45%. Prepare the slurry and disperse it for 1 hour to form the first slurry.

[0023] Step 2: Grind the first slurry using a sand mill to control the particle size to D50 = 0.29-0.31 μm. After sand milling, spray dry to obtain a spherical first solid powder.

[0024] Step 3: The first solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 550°C at a rate of 5°C / min, and held for 4 hours to obtain sample A.

[0025] Step 4: Select iron phosphate with a molar ratio of 0.96:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose and 2% PEG by mass, control the solid content at 45%, prepare the slurry and disperse it for 1 hour to form the second slurry.

[0026] Step 5: Grind the second slurry to a particle size D50 = 0.98-1.02 μm, and spray dry after grinding to obtain the second solid powder.

[0027] Step 6: The second solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 600°C at a rate of 5°C / min, and held for 5 hours to obtain sample B.

[0028] Step 7: Mix the above sample A and the above sample B at a mass ratio of 7:3 to form a slurry, and then perform sand milling to control D50 = 0.45-0.47μm. Finally, spray dry to obtain the third solid powder.

[0029] Step 8: The above-mentioned third solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 790°C at a heating rate of 5°C / min, and held at that temperature for 10 hours to obtain sample C.

[0030] Step 9: The above sample C is subjected to air jet milling to obtain high-pressure lithium iron phosphate cathode material with D50 = 1.0 μm.

[0031] The compaction density of the high-compact lithium iron phosphate cathode material obtained in this embodiment is 2.62 g / cm³. 3 The carbon content is 1.35%.

[0032] Figure 1 This is a scanning electron microscope image of the high-pressure lithium iron phosphate material in Embodiment 1 of the present invention; Figure 2 This is a charge-discharge curve of the high-pressure lithium iron phosphate material in Embodiment 1 of the present invention.

[0033] Depend on Figure 1 It can be seen that the high-compaction lithium iron phosphate cathode material prepared in Example 1 is spherical with rounded particles and a uniform distribution of particle size, which is beneficial for improving the compaction density. Figure 2 It can be seen that the high-density lithium iron phosphate cathode material has an initial charge capacity of 162.1 mAh / g at 0.1C, an initial discharge capacity of 160.1 mAh / g, an initial coulombic efficiency of 98.8%, and an initial discharge capacity of 143.8 mAh / g at 1C, demonstrating excellent electrochemical performance.

[0034] Example 2

[0035] This embodiment provides a high-pressure lithium iron phosphate cathode material and its preparation method, which includes the following steps:

[0036] Step 1: Select iron phosphate with a molar ratio of 0.98:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 9% glucose, 2.5% PEG, and 0.3% titanium dioxide by mass. Control the solid content to 45%. Prepare the slurry and disperse it for 1 hour to form the first slurry.

[0037] Step 2: Grind the first slurry using a sand mill to control the particle size to D50 = 0.29-0.31 μm. After sand milling, spray dry to obtain a spherical first solid powder.

[0038] Step 3: The first solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 600℃ at a rate of 3℃ / min, and held for 4 hours to obtain sample A.

[0039] Step 4: Select iron phosphate with a molar ratio of 0.96:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 9% glucose and 2.5% PEG by mass, control the solid content at 45%, prepare the slurry and disperse it for 1 hour to form the second slurry.

[0040] Step 5: Grind the second slurry to a particle size D50 = 0.98-1.02 μm, and spray dry after grinding to obtain the second solid powder.

[0041] Step 6: The second solid powder is calcined in a nitrogen atmosphere, with the temperature increased from room temperature to 650°C at a rate of 3°C / min, and held at that temperature for 4 hours to obtain sample B.

[0042] Step 7: Mix the above sample A and the above sample B at a mass ratio of 7:3 to form a slurry, and then perform sand milling to control D50 = 0.45-0.47μm. Finally, spray dry to obtain the third solid powder.

[0043] Step 8: The above-mentioned third solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 760°C at a heating rate of 3°C / min, and held for 10 hours to obtain sample C.

[0044] Step 9: The above sample C is subjected to air jet milling to obtain high-pressure lithium iron phosphate cathode material with D50 = 1.2 μm.

[0045] The compaction density of the high-compact lithium iron phosphate cathode material obtained in this embodiment is 2.61 g / cm³. 3 The carbon content is 1.41%.

[0046] Example 3

[0047] This embodiment provides a high-pressure lithium iron phosphate cathode material and its preparation method, which includes the following steps:

[0048] Step 1: Select iron phosphate with a molar ratio of 0.985:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.04:1. Add 8% glucose, 2% polyethylene glycol (PEG), and 0.8% titanium dioxide by mass. Control the solid content to 45%. Prepare the slurry and disperse it for 1 hour to form the first slurry.

[0049] Step 2: Grind the first slurry using a sand mill to control the particle size to D50 = 0.29-0.31 μm. After sand milling, spray dry to obtain a spherical first solid powder.

[0050] Step 3: The first solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 600°C at a rate of 5°C / min, and held for 4 hours to obtain sample A.

[0051] Step 4: Select iron phosphate with a molar ratio of 0.955:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.04:1. Add 8% glucose and 2% PEG by mass, control the solid content at 45%, prepare the slurry and disperse it for 1 hour to form the second slurry.

[0052] Step 5: Grind the second slurry to a particle size D50 = 1.15-1.20 μm, and spray dry after grinding to obtain the second solid powder.

[0053] Step 6: The second solid powder is calcined in a nitrogen atmosphere, heated from room temperature to 680°C at a heating rate of 5°C / min, and held at that temperature for 5 hours to obtain sample B.

[0054] Step 7: Mix the above sample A and the above sample B at a mass ratio of 6:4 to form a slurry, and then perform sand milling to control D50 = 0.55-0.60 μm. Finally, spray dry to obtain the third solid powder.

[0055] Step 8: The above-mentioned third solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 790°C at a heating rate of 5°C / min, and held at that temperature for 10 hours to obtain sample C.

[0056] Step 9: The above sample C is subjected to air jet milling to obtain high-pressure lithium iron phosphate cathode material with D50 = 1.15 μm.

[0057] The compaction density of the high-compact lithium iron phosphate cathode material obtained in this embodiment is 2.63 g / cm³. 3 The carbon content is 1.36%.

[0058] Comparative Example 1

[0059] This comparative example provides a lithium iron phosphate cathode material and its preparation method. The difference between this preparation method and Example 1 lies in the different particle size control during sand milling.

[0060] Specifically, the preparation method of the lithium iron phosphate cathode material in this comparative example includes the following steps:

[0061] Step 1: Select iron phosphate with a molar ratio of 0.98:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose, 2% polyethylene glycol (PEG), and 0.5% titanium dioxide by mass. Control the solid content to 45%. Prepare the slurry and disperse it for 1 hour to form the first slurry.

[0062] Step 2: Grind the first slurry using a sand mill to control the particle size to D50 = 0.15-0.2μm. After sand milling, spray dry to obtain a spherical first solid powder.

[0063] Step 3: The first solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 550°C at a rate of 5°C / min, and held for 4 hours to obtain sample A.

[0064] Step 4: Select iron phosphate with a molar ratio of 0.96:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose and 2% PEG by mass, control the solid content at 45%, prepare the slurry and disperse it for 1 hour to form the second slurry.

[0065] Step 5: Grind the second slurry to a particle size D50 = 0.98-1.02 μm, and spray dry after grinding to obtain the second solid powder.

[0066] Step 6: The second solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 600°C at a rate of 5°C / min, and held for 5 hours to obtain sample B.

[0067] Step 7: Mix the above sample A and the above sample B at a mass ratio of 7:3 to form a slurry, and then perform sand milling to control D50 = 0.45-0.47μm. Finally, spray dry to obtain the third solid powder.

[0068] Step 8: The above-mentioned third solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 790°C at a heating rate of 5°C / min, and held at that temperature for 10 hours to obtain sample C.

[0069] Step 9: The above sample C is subjected to air jet milling to obtain lithium iron phosphate cathode material with D50 = 1.0 μm.

[0070] The compaction density of the lithium iron phosphate cathode material obtained in this embodiment is 2.45 g / cm³. 3 The carbon content is 1.3%.

[0071] Comparative Example 2

[0072] This comparative example provides a lithium iron phosphate cathode material and its preparation method. The difference between this preparation method and Example 1 lies in the calcination temperature.

[0073] Specifically, the preparation method of the lithium iron phosphate cathode material in this comparative example includes the following steps:

[0074] Step 1: Select iron phosphate with a molar ratio of 0.98:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose, 2% polyethylene glycol (PEG), and 0.5% titanium dioxide by mass. Control the solid content to 45%. Prepare the slurry and disperse it for 1 hour to form the first slurry.

[0075] Step 2: Grind the first slurry using a sand mill to control the particle size to D50 = 0.29-0.31 μm. After sand milling, spray dry to obtain a spherical first solid powder.

[0076] Step 3: The first solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 550°C at a rate of 5°C / min, and held for 4 hours to obtain sample A.

[0077] Step 4: Select iron phosphate with a molar ratio of 0.96:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose and 2% PEG by mass, control the solid content at 45%, prepare the slurry and disperse it for 1 hour to form the second slurry.

[0078] Step 5: Grind the second slurry to a particle size D50 = 0.98-1.02 μm, and spray dry after grinding to obtain the second solid powder.

[0079] Step 6: The second solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 600°C at a rate of 5°C / min, and held for 5 hours to obtain sample B.

[0080] Step 7: Mix the above sample A and the above sample B at a mass ratio of 7:3 to form a slurry, and then perform sand milling to control D50 = 0.45-0.47μm. Finally, spray dry to obtain the third solid powder.

[0081] Step 8: The above-mentioned third solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 700℃ at a heating rate of 5℃ / min, and held for 10h to obtain sample C.

[0082] Step 9: The above sample C is subjected to air jet milling to obtain lithium iron phosphate cathode material with D50 = 1.0 μm.

[0083] The compaction density of the lithium iron phosphate cathode material obtained in this embodiment is 2.55 g / cm³. 3 The carbon content is 1.37%.

[0084] Comparative Example 3

[0085] This comparative example provides a lithium iron phosphate cathode material and its preparation method. The difference between this preparation method and Example 1 is that the two particles (samples) in this comparative example are directly mixed without undergoing a second calcination process, and only undergo one calcination.

[0086] Specifically, the preparation method of the lithium iron phosphate cathode material in this comparative example includes the following steps:

[0087] Step 1: Select iron phosphate with a molar ratio of 0.98:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose, 2% polyethylene glycol (PEG), and 0.5% titanium dioxide by mass. Control the solid content to 45%. Prepare the slurry and disperse it for 1 hour to form the first slurry.

[0088] Step 2: Grind the first slurry using a sand mill to control the particle size to D50 = 0.29-0.31 μm. After sand milling, spray dry to obtain a spherical first solid powder.

[0089] Step 3: The first solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 550°C at a rate of 5°C / min, and held for 4 hours to obtain sample A.

[0090] Step 4: Select iron phosphate with a molar ratio of 0.96:1 and disperse it in water. Add lithium carbonate with a molar ratio of 1.03:1. Add 8% glucose and 2% PEG by mass, control the solid content at 45%, prepare the slurry and disperse it for 1 hour to form the second slurry.

[0091] Step 5: Grind the second slurry to a particle size D50 = 0.98-1.02 μm, and spray dry after grinding to obtain the second solid powder.

[0092] Step 6: The second solid powder is calcined in a nitrogen atmosphere, and the temperature is increased from room temperature to 600°C at a rate of 5°C / min, and held for 5 hours to obtain sample B.

[0093] Step 7: Mix the above sample A and the above sample B at a mass ratio of 7:3 and perform air jet milling to obtain lithium iron phosphate cathode material with D50 = 1.0 μm.

[0094] The compaction density of the lithium iron phosphate cathode material obtained in this embodiment is 2.41 g / cm³. 3 The carbon content is 1.39%.

[0095] Table 1 shows the comparison of results from the implementation cases of this experiment.

[0096] experiment <![CDATA[Compaction (g / cm 3 )]]> Carbon content (%) Example 1 2.62 1.35 Example 2 2.61 1.41 Example 3 2.63 1.36 Comparative Example 1 2.45 1.30 Comparative Example 2 2.55 1.37 Comparative Example 3 2.41 1.39

[0097] As shown in Table 1, the compacted density of the lithium iron phosphate product prepared by this invention can reach 2.6 g / cm³. 3 The above is an explanation. In Comparative Example 1, the particle size of the small particles was adjusted, and the excessive proportion of small particles led to reduced compaction. In Comparative Examples 2 and 3, the secondary calcination temperature was lowered or the secondary calcination process was completely eliminated. The temperature was too low, resulting in poor crystallinity, numerous lattice defects, voids between particles, and poor control over morphology and size, which in turn led to low compaction.

[0098] Those skilled in the art should understand that this invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to this invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a high-pressure lithium iron phosphate cathode material, characterized in that, Includes the following steps: Step 1: Disperse ferric phosphate, lithium carbonate, glucose, polyethylene glycol (PEG), and titanium dioxide in water according to a first predetermined ratio to form a first slurry; Step 2: Grind the first slurry to the first predetermined particle size requirement and then spray dry it to obtain the first solid powder; Step 3: Calcine the first solid powder to obtain sample A; Step 4: Disperse ferric phosphate, lithium carbonate, glucose, and PEG in water according to a second predetermined ratio to form a second slurry; Step 5: Grind the second slurry to the second predetermined particle size requirement and then spray dry to obtain the second solid powder; Step 6: Calcining the second solid powder to obtain sample B; Step 7: Mix the sample A and the sample B in a third predetermined ratio to form a slurry, then grind the mixture to the third predetermined particle size requirement and spray dry it to obtain a third solid powder. Step 8: Calcining the third solid powder to obtain sample C; Step 9: After air jet milling, the sample C is used to obtain high-pressure lithium iron phosphate cathode material.

2. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1, characterized in that: in, In step 1, the iron-phosphorus molar ratio of ferric phosphate is 0.97-0.99:1, the lithium-iron molar ratio of lithium carbonate is 1.0-1.05:1, the mass addition of glucose is 6-10%, the mass addition of PEG is 1%-5%, and the mass addition of titanium dioxide is 0.2%-1%. In step 4, the iron-phosphorus molar ratio of the iron phosphate is 0.95-0.97:1, the lithium-iron molar ratio of the lithium carbonate is 1.0-1.05:1, the mass addition of glucose is 6-10%, and the mass addition of PEG is 1%-5%.

3. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 2, the first predetermined particle size requirement is D50 = 0.2-0.5 μm.

4. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 3, the heating rate of the calcination is 2℃ / min-10℃ / min, the temperature is 500℃ / min-700℃, and the holding time is 2℃ / min-5h.

5. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 5, the second predetermined particle size requirement is D50 = 0.8 μm - 1.3 μm.

6. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 6, the heating rate of the calcination is 2℃ / min-10℃ / min, the temperature is 500℃-700℃, and the holding time is 2h-5h.

7. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 7, the mass ratio of sample A to sample B is 5:5-9:1, and the third predetermined particle size requirement is D50 = 0.4-0.6 μm.

8. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 8, the heating rate of the calcination is 2℃ / min-10℃ / min, the temperature is 750℃-850℃, and the holding time is 5h-15h.

9. The method for preparing high-pressure lithium iron phosphate cathode material according to claim 1 or 2, characterized in that: in, In step 9, the final product after air jet milling has a D50 of 0.8μm-1.5μm.

10. A high-pressure lithium iron phosphate cathode material, characterized in that, It is prepared by the high-pressure lithium iron phosphate cathode material preparation method according to any one of claims 1-9.

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