Lithium iron phosphate positive electrode material, lithium ion battery and preparation method

Abstract

The application discloses a lithium iron phosphate positive material, a lithium ion battery and a preparation method. The lithium iron phosphate positive material is synthesized by using iron phosphate and iron hydroxide as mixed iron sources and adopting a two-step method. In the first step, two raw materials are respectively ground into one kind of large particle size and one kind of small particle size. The large particle size is prepared by sintering at two different temperatures to obtain large particles and medium particles. The small particle size is prepared by sintering at two different temperatures to obtain small particles and extremely small particles. In the second step, the four kinds of particles are dry mixed according to a certain proportion. A carbon source solution is introduced during the sintering process to perform CVD carbon source coating, so that the carbon source coating effect is improved. After sintering, the lithium iron phosphate positive material is obtained. By means of dry mixing of multi-stage particles, once sintering of high carbon content and twice sintering of CVD coating, high compaction and high capacity can be realized, the coating effect of the particles is effectively improved, and the manufacturing cost is greatly reduced.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a lithium iron phosphate cathode material, a lithium-ion battery, and a preparation method thereof. Background Technology

[0002] With the global energy structure transformation and the advancement of "dual carbon" goals, lithium-ion batteries are increasingly widely used in new energy vehicles, large-scale energy storage systems, and portable electronic devices. Among them, lithium iron phosphate has become the mainstream cathode material for power batteries and energy storage batteries due to its core advantages such as high theoretical specific capacity, excellent thermal stability, low cost, environmental friendliness, and long cycle life. However, the rapid development of the new energy industry has placed higher demands on battery performance, which is determined by the compaction density and capacity performance of the cathode material. Compaction density directly determines the amount of active material filled per unit volume and is a key indicator for improving battery energy density, while high capacity is a core prerequisite for ensuring range and energy storage efficiency.

[0003] Currently, high-performance lithium iron phosphate is commonly prepared using a single precursor. However, the material reaction mechanisms and temperatures of the same precursor process are similar, which significantly affects the design particle size distribution and prevents the optimal performance from being achieved. This invention uses a composite product of iron phosphate and iron hydroxide as a precursor. Due to the inherent material properties of iron phosphate and iron hydroxide, the precursor already exhibits particle size distribution. Furthermore, by utilizing the difference in their reaction temperatures, the particle size distribution is increased, significantly improving the performance of the lithium iron phosphate cathode material. Summary of the Invention

[0004] The purpose of this invention is to provide a lithium iron phosphate cathode material, a lithium-ion battery, and a preparation method. Using iron phosphate and iron hydroxide as a mixed iron source, a two-step synthesis method is employed. The two raw materials are ground to a large particle size and a small particle size, respectively. The large particle size is sintered at two different temperatures to prepare large and medium particles, while the small particle size is sintered at two different temperatures to prepare small and ultra-small particles. The four types of particles are then dry-mixed in a certain proportion. During the sintering process, a carbon source solution is introduced for CVD carbon source coating to improve the carbon source coating effect. Sintering yields the lithium iron phosphate cathode material.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides a method for preparing a lithium iron phosphate cathode material, comprising the following steps: A first iron source, lithium source, phosphorus source, carbon source, dopant, and deionized water are mixed in a certain proportion, and after a first grinding and spray drying, a first precursor powder is obtained; a portion of the first precursor powder is sintered at a first temperature and then pulverized by airflow to obtain a first intermediate; another portion of the first precursor powder is sintered at a second temperature and then pulverized by airflow to obtain a second intermediate. The second iron source, lithium source, phosphorus source, carbon source, dopant, and deionized water are mixed in proportion, and after a second grinding and spray drying, a second precursor powder is obtained; a portion of the second precursor powder is sintered at a third temperature and then pulverized by airflow to obtain a third intermediate; another portion of the second precursor powder is sintered at a fourth temperature and then pulverized by airflow to obtain a fourth intermediate. The first intermediate, the second intermediate, the third intermediate, and the fourth intermediate are dry-mixed in proportion and sintered at a fifth temperature. During sintering, a third carbon source solution with anhydrous ethanol as a solvent is added, and the concentration of the third carbon source solution is maintained at 500 g / L. Then, the mixture is subjected to air jet milling to obtain the lithium iron phosphate cathode material with a D50 particle size of 0.8~1.4 μm. The first intermediate has an average primary particle size of 800-1200 nm; the second intermediate has an average primary particle size of 500-700 nm; the third intermediate has an average primary particle size of 200-400 nm; and the fourth intermediate has an average primary particle size of 100-200 nm. The first and second iron sources include iron phosphate and iron oxide hydroxide, wherein the specific surface area of ​​the iron phosphate is 4-16 m². 2 / g, with an Fe / P molar ratio of 0.960–0.980, and the specific surface area of ​​the ferric hydroxide is 20–300 m² / g. 2 / g, wherein the ratio of ferric phosphate to ferric hydroxide is 9:1 to 1:9.

[0006] In some possible implementations, the first and second lithium sources are battery-grade lithium sources, including one or more of lithium carbonate, lithium phosphate, lithium hydroxide, and lithium dihydrogen phosphate; and the first and second phosphorus sources are battery-grade phosphorus sources, including one or more of iron phosphate, lithium phosphate, lithium dihydrogen phosphate, phosphoric acid, and ammonium monohydrogen phosphate. The amounts of the first and second lithium sources added are determined according to the Li / Fe molar ratio of the lithium iron phosphate cathode material being 1.02 to 1.06; the amounts of the first and second phosphorus sources added are determined according to the Fe / P molar ratio of the lithium iron phosphate cathode material being 0.965 to 0.975.

[0007] In some possible implementations, the first and second carbon sources include one or more of glucose, PEG, citric acid, and sucrose, and the carbon content of the first and second precursor powders is 0.8~1.2 wt%. The third carbon source solution includes one or more of polyethylene solution, PVP solution, PVDF solution, starch solution, PEG solution, sucrose solution, and glucose solution; the carbon content of the high-pressure, high-capacity lithium iron phosphate cathode material is 1.2~1.6wt%.

[0008] In some possible implementations, the first and second dopants each include one or more of titanium dioxide, ammonium metavanadate, niobium pentoxide, and manganese oxide; the content of the doping element in the first precursor powder is 1500~4000ppm, and the content of the doping element in the first precursor powder is 5000~7000ppm.

[0009] In some possible implementations, the first, second, third, and fourth intermediates are mixed in a ratio of 2~4:2~4:1~3:1~3.

[0010] In some possible implementations, the spray drying specifically includes: setting the inlet temperature to 180–240°C and the outlet temperature to 80–140°C; controlling the D50 particle size of the first, second, and third precursor powders to be 20–60 μm and the moisture content to be ≤1.5%.

[0011] In some possible implementations, the first, second, third, fourth, and fifth temperature sintering are all carried out under a protective gas, which is an inert gas; The first temperature sintering specifically includes: setting the temperature to 800~840℃ and the holding period to 7~11h; The second temperature sintering specifically includes: setting the temperature to 740~780℃ and holding the temperature for 7~11 hours; The third temperature sintering specifically includes: setting the temperature to 720~760℃ and holding the temperature for 4~7 hours; The fourth temperature sintering specifically includes: setting the temperature to 660~700℃ and holding the temperature for 4~7 hours; The fifth temperature sintering specifically includes setting the temperature to 740~780℃ and the holding period to 6~10h.

[0012] In some possible implementations, the first grinding specifically includes: setting the temperature to 10–45°C, grinding to a D50 particle size of 0.8–1.2 μm, and a solid content of 30–50 wt%. The second grinding process specifically includes: setting the temperature to 10–45°C, grinding to a D50 particle size of 0.2–0.5 μm, and a solid content of 30–50 wt%. The dry mixing method specifically includes: using a high-speed mixer, with mixing parameters set to 30~50Hz and mixing time of 30~50min.

[0013] In a second aspect, the present invention provides a lithium iron phosphate cathode material, wherein the lithium iron phosphate cathode material is prepared by the preparation method described in any one of the first aspects.

[0014] Thirdly, the present invention also provides a lithium-ion battery, the lithium-ion battery comprising a lithium-ion battery cathode made based on the lithium iron phosphate cathode material described in the second aspect.

[0015] The lithium iron phosphate cathode material, lithium-ion battery, and preparation method provided by this invention have the following advantages compared with the prior art: 1. This invention uses ferric phosphate and ferric hydroxide as a composite precursor and imposes restrictions on them. Due to the inherent material properties of ferric phosphate and ferric hydroxide, the precursor already exhibits particle size distribution. By utilizing the difference in their reaction temperature, the quantity of particle size distribution is increased, and more free phosphate ions are introduced, thereby improving particle roundness. Figure 1 As shown.

[0016] 2. The preparation method of this invention involves one grinding and two sintering processes. High-pressure compaction and high-capacity are achieved through a mixture of large, medium, small, and extremely small particles. As shown in Table 1, the ≥2.7 g / cm³ of this invention... 3 The powder resistivity is as low as 4.2 Ω·cm, and the first discharge capacity at 1.0C is higher than 142 mAh / g, which reflects the characteristics of high pressure, high capacity and low internal resistance of this invention.

[0017] 3. In the first sintering of this invention, a conventional carbon source is selected to obtain a high carbon content. In the second sintering, CVD coating is used to catalyze the transition metal to directionally coat the weakly coated carbon source sites (where Fe atoms are exposed, indicating weak coating) and obtain more graphene phase, effectively improving the coating effect of the particles and achieving high capacity and low internal resistance. This invention changes the two wet mixing processes to one wet mixing process plus one dry mixing process, which reduces the production cost while maintaining the performance of lithium iron phosphate cathode material. Attached Figure Description

[0018] Figure 1 Here is a SEM image of the lithium iron phosphate cathode material prepared in Example 1; Figure 2 The graph shows the charge-discharge performance of the lithium iron phosphate cathode material prepared in Example 1. Detailed Implementation

[0019] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application. At the same time, in the description of the embodiments of this application, the terms "first," "second," etc., are only used to distinguish descriptions and should not be construed as indicating or implying relative importance. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0020] Example 1 This embodiment provides a lithium iron phosphate cathode material, the preparation method of which includes the following steps: S1, 3000g ferric phosphate, 980g ferric hydroxide (specific surface area 150m²) 2 1174.4g lithium phosphate, 120.4g phosphoric acid, 300g glucose, 132.4g PEG, 24.31g titanium dioxide, and 8440g deionized water were mixed and ground at 20°C until the D50 particle size was 1.0μm and the solid content was 40wt%. The mixture was then spray-dried to obtain a first precursor powder. A portion of the first precursor powder was sintered at a first temperature of 820°C for 9 hours and then pulverized by air jet milling to obtain a first intermediate with an average primary particle size of 1000nm. Another portion of the first precursor powder was sintered at a second temperature of 760°C for 9 hours and then pulverized by air jet milling to obtain a second intermediate with an average primary particle size of 600nm. S2, 3000g ferric phosphate, 980g ferric hydroxide (specific surface area 100m²) 2 1174.4g lithium phosphate, 120.4g phosphoric acid, 300g glucose, 132.4g PEG, 44.2g titanium dioxide, and 8440g deionized water were mixed and then ground at 20℃ until the D50 particle size was 0.35μm and the solid content was 40wt%. The mixture was then spray-dried to obtain a second precursor powder. A portion of the second precursor powder was sintered at a third temperature of 740℃ for 5.5h and then air-jet milled to obtain a third intermediate with an average primary particle size of 300nm. Another portion of the second precursor powder was sintered at a fourth temperature of 680℃ for 5.5h and then air-jet milled to obtain a fourth intermediate with an average primary particle size of 150nm. S3. Mix 1200g of the first intermediate, 1200g of the second intermediate, 800g of the third intermediate, and 800g of the fourth intermediate in a dry manner according to the ratio. Use a high-speed mixer to mix the materials. Set the mixing parameters to 40Hz and the mixing time to 40min. Perform sintering at the fifth temperature. Set the temperature to 760℃ and the holding period to 7h. During sintering, add a dispersion formed by dispersing 40g of PVP with 80mL of anhydrous ethanol as the solvent. Then perform air jet milling to obtain lithium iron phosphate cathode material with a D50 particle size of 1.1μm and a carbon content of 1.3wt%.

[0021] The specific surface area of ​​iron phosphate is 10 m². 2 / g, with a Fe / P molar ratio of 0.970.

[0022] Spray drying specifically includes: setting the inlet temperature to 210℃ and the outlet temperature to 110℃; controlling the D50 particle size of the first and second precursor powders to 40μm and the moisture content to ≤1.5%.

[0023] Sintering at the first, second, third, fourth, and fifth temperatures is carried out under a protective gas, which in this embodiment is nitrogen.

[0024] Example 2 This embodiment provides a lithium iron phosphate cathode material, the preparation method of which includes the following steps: S1, 3000g iron phosphate, 1251g iron hydroxide, 1273.5g lithium phosphate, 325.9g phosphoric acid, 244g sucrose, 146g PEG, 32.6g titanium dioxide, and 13880g deionized water were mixed and ground at 10℃ until the D50 particle size was 0.8μm and the solid content was 30wt%. The mixture was then spray-dried to obtain a first precursor powder. A portion of the first precursor powder was sintered at a first temperature of 800℃ for 11 hours and then pulverized by air jet milling to obtain a first intermediate with an average primary particle size of 800nm. Another portion of the first precursor powder was sintered at a second temperature of 780℃ for 7 hours and then pulverized by air jet milling to obtain a second intermediate with an average primary particle size of 500nm. S2, 3000g iron phosphate, 1251g iron hydroxide, 1273.5g lithium phosphate, 325.9g phosphoric acid, 244g sucrose, 146g PEG, 40.8g titanium dioxide, and 13880g deionized water were mixed and then ground at 10℃ until the D50 particle size was 0.2μm and the solid content was 30wt%. The mixture was then spray-dried to obtain a second precursor powder. A portion of the second precursor powder was sintered at a third temperature of 720℃ for 7 hours and then pulverized by air jet milling to obtain a third intermediate with an average primary particle size of 200nm. Another portion of the second precursor powder was sintered at a fourth temperature of 660℃ for 7 hours and then pulverized by air jet milling to obtain a fourth intermediate with an average primary particle size of 100nm. S3. Mix 800g of the first intermediate, 1600g of the second intermediate, 1200g of the third intermediate, and 400g of the fourth intermediate in a dry manner according to the ratio. Use a high-speed mixer to mix the materials. Set the mixing parameters to 30Hz and the mixing time to 50min. Perform sintering at the fifth temperature of 740℃ and hold for 10h. During sintering, add a dispersion of 40g of PVP in 80mL of anhydrous ethanol as a solvent. Then perform air jet milling to obtain lithium iron phosphate cathode material with a D50 particle size of 0.8μm and a carbon content of 1.1wt%.

[0025] The specific surface area of ​​iron phosphate is 4 m². 2 / g, its Fe / P molar ratio is 0.960, and the specific surface area of ​​ferric hydroxide is 300m². 2 / g.

[0026] Spray drying specifically includes: setting the inlet temperature to 240℃ and the outlet temperature to 140℃; controlling the D50 particle size of the first and second precursor powders to 20μm and the moisture content to ≤1.5%.

[0027] Sintering at the first, second, third, fourth, and fifth temperatures is carried out under a protective gas, which in this embodiment is nitrogen.

[0028] Example 3 This embodiment provides a lithium iron phosphate cathode material, the preparation method of which includes the following steps: S1, 3000g iron phosphate, 711g iron hydroxide, 996.8g lithium phosphate, 92.2g lithium carbonate, 268.9g sucrose, 257g citric acid, 9.9g titanium dioxide, and 5340g deionized water are mixed and ground at 30℃ until the D50 particle size is 1.2μm and the solid content is 50wt%. The mixture is then spray-dried to obtain a first precursor powder. A portion of the first precursor powder is sintered at 840℃ for 7 hours using air jet milling to obtain a first intermediate with an average primary particle size of 1200nm. Another portion of the first precursor powder is sintered at 740℃ for 11 hours using air jet milling to obtain a second intermediate with an average primary particle size of 700nm. S2, 3000g iron phosphate, 711g iron hydroxide, 996.8g lithium phosphate, 92.2g lithium carbonate, 268.9g sucrose, 257g citric acid, 39.6g titanium dioxide, and 5340g deionized water were mixed and then ground at 30℃ until the D50 particle size was 0.3μm and the solid content was 50wt%. The mixture was then spray-dried to obtain a second precursor powder. A portion of the second precursor powder was sintered at a third temperature of 760℃ for 4 hours and then pulverized by air jet milling to obtain a third intermediate with an average primary particle size of 400nm. Another portion of the second precursor powder was sintered at a fourth temperature of 700℃ for 4 hours and then pulverized by air jet milling to obtain a fourth intermediate with an average primary particle size of 200nm. S3. Mix 1200g of the first intermediate, 800g of the second intermediate, 1200g of the third intermediate, and 800g of the fourth intermediate in a dry manner according to the ratio. Use a high-speed mixer to mix the materials. Set the mixing parameters to 50Hz and the mixing time to 30min. Perform sintering at the fifth temperature. Set the temperature to 780℃ and the holding period to 6h. During sintering, add a dispersion formed by dispersing 40g of PVP with 80mL of anhydrous ethanol as the solvent. Then perform air jet milling to obtain lithium iron phosphate cathode material with a D50 particle size of 1.4μm and a carbon content of 1.6wt%.

[0029] The specific surface area of ​​iron phosphate is 16 m². 2 / g, its Fe / P molar ratio is 0.980, and the specific surface area of ​​ferric hydroxide is 20m². 2 / g.

[0030] Spray drying specifically includes: setting the inlet temperature to 180℃ and the outlet temperature to 80℃; controlling the D50 particle size of the first and second precursor powders to 60μm and the moisture content to ≤1.5%.

[0031] Sintering at the first, second, third, fourth, and fifth temperatures is carried out under a protective gas, which in this embodiment is nitrogen.

[0032] Comparative Example 1 The only difference between this comparative example and Example 1 is that iron hydroxide in the raw materials is replaced with iron phosphate, lithium phosphate is replaced with lithium carbonate, and the elemental molar ratio of the first and second precursor powders remains unchanged.

[0033] Comparative Example 2 The only difference between this comparative example and Example 1 is that another portion of the first precursor powder is sintered at a second temperature of 820°C for a holding period of 9 hours, followed by airflow pulverization to obtain the second intermediate.

[0034] Comparative Example 3 The only difference between this comparative example and Example 1 is that a portion of the second precursor powder is sintered at a third temperature of 680°C for 5.5 hours, followed by airflow pulverization to obtain the third intermediate.

[0035] The following tests were performed on Examples 1-3 and Comparative Examples 1-3: 1. Take 10kx scanning electron microscope images of the lithium iron phosphate cathode materials prepared in Examples 1-3 and Comparative Examples 1-3; 2. Weigh 1g of each of the lithium iron phosphate cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 and place them into a compaction mold. Place the mold into the compaction equipment to start the test. Take the result under 30KN pressure as the powder compaction density. 3. The lithium iron phosphate cathode materials prepared in Examples 1-3 and Comparative Examples 1-3 were dispersed in NMP with Super-P and PVDF at a mass ratio of 80:10:10. After ball milling and uniform dispersion, the dispersion was coated on aluminum foil and vacuum dried to obtain the cathode electrode. The electrolyte was 1 mol / L LiPF6, with a solvent volume ratio of EC:DMC:EMC = 1:1:1 (volume ratio). The separator was Celgard polypropylene membrane, and the lithium metal sheet was used as the anode. All materials were assembled into a coin cell. The test voltage range was 2.0V-3.75V. The cells were charged to 3.75V using a constant current and constant voltage charging method, and discharged to 2.0V using a constant current discharging method. The charge / discharge current was 0.1C for 1 cycle; then, the cells were charged / discharged at 1C for 3 cycles, with the cutoff voltage condition the same as at 0.1C.

[0036] The test results are shown in Table 1: Table 1 Test Results As shown in Table 1, under the same test conditions, the lithium iron phosphate cathode materials prepared in Examples 1-3 of this invention exhibit significantly lower powder resistivity compared to Comparative Examples 1-3, and the powder compaction degree of the lithium iron phosphate cathode materials prepared in Examples 1-3 all reaches 2.7 g / cm³. 3This meets the requirements of fifth-generation lithium iron phosphate materials for powder compaction. At the same time, the 1.0C first discharge capacity of the lithium iron phosphate cathode materials prepared in Examples 1-3 is also significantly higher than that of Comparative Examples 1-3.

[0037] Obviously, those skilled in the art can make various modifications and variations to the embodiments of the present invention without departing from the spirit and scope of the invention. Therefore, if these modifications and variations fall within the scope of the claims of the present invention and their equivalents, the present invention also intends to include these modifications and variations.

Claims

1. A method for preparing a lithium iron phosphate cathode material, characterized in that, Includes the following steps: A first iron source, lithium source, phosphorus source, carbon source, dopant, and deionized water are mixed in a certain proportion, and after a first grinding and spray drying, a first precursor powder is obtained; a portion of the first precursor powder is sintered at a first temperature and then pulverized by airflow to obtain a first intermediate; another portion of the first precursor powder is sintered at a second temperature and then pulverized by airflow to obtain a second intermediate. The second iron source, lithium source, phosphorus source, carbon source, dopant, and deionized water are mixed in proportion, and after a second grinding and spray drying, a second precursor powder is obtained; a portion of the second precursor powder is sintered at a third temperature and then pulverized by airflow to obtain a third intermediate; another portion of the second precursor powder is sintered at a fourth temperature and then pulverized by airflow to obtain a fourth intermediate. The first intermediate, the second intermediate, the third intermediate, and the fourth intermediate are dry-mixed in proportion and sintered at a fifth temperature. During sintering, a third carbon source solution with anhydrous ethanol as solvent is added and the solution concentration is maintained at 500 g / L. Then, the mixture is subjected to air jet milling to obtain the lithium iron phosphate cathode material with a D50 particle size of 0.8~1.4 μm. The first intermediate has an average primary particle size of 800-1200 nm; the second intermediate has an average primary particle size of 500-700 nm; the third intermediate has an average primary particle size of 200-400 nm; and the fourth intermediate has an average primary particle size of 100-200 nm. The first and second iron sources include iron phosphate and iron oxide hydroxide, wherein the iron phosphate has a specific surface area of ​​4-16 m². 2 / g, with an Fe / P molar ratio of 0.960–0.980, and the specific surface area of ​​the ferric hydroxide is 20–300 m² / g. 2 / g, wherein the ratio of ferric phosphate to ferric hydroxide is 9:1 to 1:

9.

2. The preparation method according to claim 1, characterized in that, The first and second lithium sources are battery-grade lithium sources, including one or more of lithium carbonate, lithium phosphate, lithium hydroxide, and lithium dihydrogen phosphate. The first and second phosphorus sources are battery-grade phosphorus sources, including one or more of iron phosphate, lithium phosphate, lithium dihydrogen phosphate, phosphoric acid, and ammonium monohydrogen phosphate. The amounts of the first and second lithium sources added are determined according to the Li / Fe molar ratio of the lithium iron phosphate cathode material being 1.02 to 1.06; the amounts of the first and second phosphorus sources added are determined according to the Fe / P molar ratio of the lithium iron phosphate cathode material being 0.965 to 0.

975.

3. The preparation method according to claim 1, characterized in that, The first and second carbon sources include one or more of glucose, PEG, citric acid, and sucrose, and the carbon content of the first and second precursor powders is 0.8~1.2wt%. The third carbon source solution includes one or more of polyethylene solution, PVP solution, PVDF solution, starch solution, PEG solution, sucrose solution, and glucose solution; the carbon content of the high-pressure, high-capacity lithium iron phosphate cathode material is 1.2~1.6wt%.

4. The preparation method according to claim 1, characterized in that, Both the first and second dopants include one or more of titanium dioxide, ammonium metavanadate, niobium pentoxide, and manganese oxide; the content of the doping element in the first precursor powder is 1500~4000ppm, and the content of the doping element in the first precursor powder is 5000~7000ppm.

5. The preparation method according to claim 1, characterized in that, The first, second, third, and fourth intermediates are mixed in a ratio of 2~4:2~4:1~3:1~3.

6. The preparation method according to claim 1, characterized in that, The spray drying specifically includes: setting the inlet temperature to 180-240℃ and the outlet temperature to 80-140℃; controlling the D50 particle size of the first, second, and third precursor powders to be 20-60μm and the moisture content to ≤1.5%.

7. The preparation method according to claim 1, characterized in that, The sintering at the first, second, third, fourth, and fifth temperatures is all carried out under a protective gas, which is an inert gas. The first temperature sintering specifically includes: setting the temperature to 800~840℃ and the holding period to 7~11h; The second temperature sintering specifically includes: setting the temperature to 740~780℃ and holding the temperature for 7~11 hours; The third temperature sintering specifically includes: setting the temperature to 720~760℃ and holding the temperature for 4~7 hours; The fourth temperature sintering specifically includes: setting the temperature to 660~700℃ and holding the temperature for 4~7 hours; The fifth temperature sintering specifically includes setting the temperature to 740~780℃ and the holding period to 6~10h.

8. The preparation method according to claim 1, characterized in that, The first grinding process specifically includes: setting the temperature to 10–45°C, grinding to a D50 particle size of 0.8–1.2 μm, and a solid content of 30–50 wt%. The second grinding process specifically includes: setting the temperature to 10–45°C, grinding to a D50 particle size of 0.2–0.5 μm, and a solid content of 30–50 wt%. The dry mixing method specifically includes: using a high-speed mixer, with mixing parameters set to 30~50Hz and mixing time of 30~50min.

9. A lithium iron phosphate cathode material, characterized in that, The lithium iron phosphate cathode material is prepared by the preparation method according to any one of claims 1-8.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes a lithium-ion battery cathode made based on the lithium iron phosphate cathode material of claim 9.

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