A high-compaction high-capacity lithium iron phosphate positive electrode material and a preparation method thereof

Abstract

The application discloses a high-compaction high-capacity lithium iron phosphate positive electrode material and a preparation method thereof. The lithium iron phosphate positive electrode material is synthesized by using iron phosphate and iron hydroxide as mixed iron sources and adopting a two-step method. In the first step, raw materials are ground to a certain particle size and are divided into four parts, and large particles, medium particles, small particles and extremely small particles are prepared by sintering at four temperatures. In the second step, the large particles and the medium particles are mixed and ground to a large-size slurry, the small particles and the extremely small particles are mixed and ground to a small-size slurry, the two kinds of slurries are mixed, spray drying is carried out, sintering is carried out, and crushing is carried out to obtain the high-compaction high-capacity lithium iron phosphate. The multiple particles are mixed and ground in the application, so that the compaction density of the positive electrode material is further increased; low-molecular carbon sources are selected for primary sintering, which is beneficial to particle coating and improves particle roundness; and high-molecular carbon sources are selected for secondary sintering, so that a continuous conductive network is constructed, and the capacity of the material is ensured.

Description

Technical Field

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

[0002] With the global energy structure transformation, 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 high-pressure, high-capacity lithium iron phosphate cathode material and its preparation method. Iron phosphate and iron hydroxide are used as iron sources. The raw materials are ground to a certain particle size and divided into four parts. Large particles, medium particles, small particles and ultra-small particles are prepared by sintering at four different temperatures. The large and medium particles are then mixed and ground into a large-particle slurry, and the small and ultra-small particles are mixed and ground into a small-particle slurry. The two slurries are then mixed, spray-dried, sintered, and pulverized to obtain high-pressure, high-capacity lithium iron phosphate.

[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 high-pressure, high-capacity lithium iron phosphate cathode material, comprising the following steps: Iron source, lithium source, phosphorus source, first carbon source, dopant, and deionized water are mixed in proportion, ground in the first stage, and spray-dried to obtain a first precursor powder; a first portion of the first precursor powder is sintered at a first temperature and then pulverized by airflow to obtain a first intermediate; a second portion of the first precursor powder is sintered at a second temperature and then pulverized by airflow to obtain a second intermediate; a third portion of the first precursor powder is sintered at a third temperature and then pulverized by airflow to obtain a third intermediate; and a fourth portion of the first 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 second carbon source, and deionized water are mixed in a certain proportion and then ground in a second process to obtain a first slurry; the third intermediate, the fourth intermediate, the third carbon source, and deionized water are mixed in a certain proportion and then ground in a third process to obtain a second slurry. The first and second slurries are mixed and spray-dried to obtain the second precursor powder, which is then sintered at a fifth temperature and pulverized by airflow to obtain the high-pressure, high-capacity lithium iron phosphate cathode material with a D50 particle size of 0.8~1.2μm. The first intermediate has an average primary particle size of 1500~2000nm; the second intermediate has an average primary particle size of 800~1200nm; the third intermediate has an average primary particle size of 300~600nm; and the fourth intermediate has an average primary particle size of 50~150nm. The iron source includes ferric phosphate and ferric hydroxide, wherein the ferric 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.

[0006] In some possible implementations, the lithium source is a battery-grade lithium source, including one or more of lithium carbonate, lithium phosphate, lithium hydroxide, and lithium dihydrogen phosphate, and the phosphorus source is a battery-grade phosphorus source, including one or more of iron phosphate, lithium phosphate, lithium dihydrogen phosphate, phosphoric acid, and ammonium monohydrogen phosphate. The amount of lithium source added is determined according to the Li / Fe molar ratio of the high-pressure, high-capacity lithium iron phosphate cathode material being 1.01 to 1.05, and the amount of phosphorus source added is determined according to the Fe / P molar ratio of the high-pressure, high-capacity lithium iron phosphate cathode material being 0.965 to 0.975.

[0007] In some possible implementations, the first carbon source includes one or more of glucose, PEG, citric acid, and sucrose, and the carbon content of the first precursor powder is 0.02~0.7wt%. The second and third carbon sources include one or more of polyethylene, PVP, PVDF, starch, PET, and polyamide; the carbon content of the high-pressure, high-capacity lithium iron phosphate cathode material is 1.1~1.5wt%.

[0008] In some possible implementations, the dopant includes one or more of titanium dioxide, ammonium metavanadate, niobium pentoxide, and manganese oxide; the content of the dopant element in the first precursor powder is 3000~6000ppm.

[0009] In some possible implementations, the first intermediate and the second intermediate are mixed in a ratio of 2~4:2~4, and the third intermediate and the fourth intermediate are mixed in a ratio of 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 and second precursor powders to be 20–60 μm and the moisture content to ≤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 800~830℃ and the holding period to 5~11h; The second temperature sintering specifically includes: setting the temperature to 740~800℃ and holding the temperature for 5~11 hours; The third temperature sintering specifically includes: setting the temperature to 660~740℃ and holding the temperature for 5~11 hours; The fourth temperature sintering specifically includes: setting the temperature to 450~600℃ and holding the temperature for 5~11 hours; The fifth temperature sintering specifically includes setting the temperature to 750~810℃ 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 0.3–0.7 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 0.8–1.4 μm, and a solid content of 30–50 wt%. The third grinding process specifically includes: setting the temperature to 10-45℃, grinding to a D50 particle size of 0.1-0.5μm, and a solid content of 30-50wt%.

[0013] In a second aspect, the present invention provides a high-pressure, high-capacity lithium iron phosphate cathode material, wherein the high-pressure, high-capacity 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 high-pressure, high-capacity lithium iron phosphate cathode material described in the second aspect.

[0015] The present invention provides a high-pressure, high-capacity lithium iron phosphate cathode material and its preparation method, which have the following advantages compared with the prior art: 1. This invention uses ferric phosphate and ferric hydroxide as composite precursors and imposes restrictions on them. Due to the material characteristics of ferric phosphate and ferric hydroxide, the precursors have already produced particle size distribution. At the same time, the difference in their reaction temperature is used to increase the number of particle sizes.

[0016] 2. In composite precursors, more free phosphate groups can be introduced, which improves the temperature sensitivity of the precursor and enables the sintering of a single precursor into different particles at different temperatures.

[0017] 3. The preparation method of this invention involves two grinding and two sintering processes. Large and medium particles are ground to a large particle size, while small and extremely small particles are ground to a small particle size, which improves the accuracy of particle size distribution. As shown in Table 1, the particle size distribution of this invention is ≥2.7 g / cm³. 3 The powder resistivity is as low as 4.2 Ω·cm, and the first discharge capacity at 1.0C is higher than 141.9 mAh / g, which reflects the characteristics of high pressure, high capacity and low internal resistance of this invention.

[0018] 4. In the first sintering of this invention, a low-molecular-weight carbon source is used to improve particle coating and enhance particle roundness; in the second sintering, a high-molecular-weight carbon source is used to construct a continuous conductive network to ensure the material's performance. Attached Figure Description

[0019] 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

[0020] 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.

[0021] Example 1 This embodiment provides a high-pressure, high-capacity lithium iron phosphate cathode material, the preparation method of which includes the following steps: S1, 3000g ferric phosphate, 897g ferric hydroxide, 1134.8g lithium phosphate, 59.2g phosphoric acid, 150g sucrose, 86.1g polyethylene glycol, 32.3g titanium dioxide, and 8045g deionized water are mixed and ground at 20℃ until the D50 particle size is 0.5μm and the solid content is 40wt%. The mixture is then spray-dried to obtain the first precursor powder. The first portion of the first precursor powder is sintered at 815℃ for 8 hours using air jet milling to obtain the second precursor powder with an average primary particle size of 1700nm. The first intermediate is prepared by sintering the first precursor powder at a second temperature of 770°C for 8 hours, followed by air jet milling to obtain a second intermediate with an average primary particle size of 1000 nm. The second intermediate is prepared by sintering the first precursor powder at a third temperature of 700°C for 8 hours, followed by air jet milling to obtain a third intermediate with an average primary particle size of 450 nm. The third intermediate is prepared by sintering the first precursor powder at a fourth temperature of 520°C for 8 hours, followed by air jet milling to obtain a fourth intermediate with an average primary particle size of 100 nm.

[0022] S2. Mix 1200g of the first intermediate, 1200g of the second intermediate, 112g of PVP, and 3600g of deionized water in a certain proportion, and then grind them in a third process at a temperature of 20℃ until the D50 particle size is 1.1μm and the solid content is 40wt%, to obtain the first slurry. Mix 800g of the third intermediate, 800g of the fourth intermediate, 112g of PVP, and 2400g of deionized water in a certain proportion, and then grind them in a fourth process at a temperature of 20℃ until the D50 particle size is 0.3μm and the solid content is 40wt%, to obtain the second slurry.

[0023] S3. The first and second slurries are mixed and spray-dried to obtain the second precursor powder. Then, the powder is sintered at the fifth temperature of 780℃ for 8 hours and air-jet pulverized to obtain a high-capacity lithium iron phosphate cathode material with a D50 particle size of 1.0μm and a carbon content of 1.3wt%.

[0024] The specific surface area of ​​iron phosphate is 10 m². 2 / g, its Fe / P molar ratio is 0.970, and the specific surface area of ​​ferric hydroxide is 100m². 2 / g.

[0025] 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%.

[0026] Sintering at the first, second, third, fourth, and fifth temperatures is carried out under a protective gas, which in this embodiment is nitrogen.

[0027] Example 2 This embodiment provides a high-pressure, high-capacity lithium iron phosphate cathode material, the preparation method of which includes the following steps: S1, 3000g ferric phosphate, 1039g ferric hydroxide, 1175.2g lithium phosphate, 189.3g phosphoric acid, 145.5g glucose, 90.9g citric acid, 22.8g titanium dioxide, and 13230g deionized water are mixed and ground at 10℃ until the D50 particle size is 0.3μm and the solid content is 30wt%. The mixture is then spray-dried to obtain the first precursor powder. The first portion of the first precursor powder is sintered at 800℃ for 11 hours using air jet milling to obtain an average primary particle size of 1500 nm. The first intermediate is formed by sintering the first precursor powder at a second temperature of 740°C for 11 hours, followed by air jet milling to obtain a second intermediate with an average primary particle size of 800 nm. The third intermediate is formed by sintering the first precursor powder at a third temperature of 660°C for 11 hours, followed by air jet milling to obtain a third intermediate with an average primary particle size of 300 nm. The fourth intermediate is formed by sintering the first precursor powder at a fourth temperature of 450°C for 11 hours, followed by air jet milling to obtain a fourth intermediate with an average primary particle size of 50 nm.

[0028] S2. Mix 1600g of the first intermediate, 800g of the second intermediate, 100g of PVP, 80g of PEG, and 5600g of deionized water in a certain proportion, and then grind them in a third process at a temperature of 10℃ until the D50 particle size is 0.8μm and the solid content is 30wt% to obtain the first slurry. Mix 800g of the third intermediate, 800g of the fourth intermediate, 100g of PVP, 80g of PEG, and 3733g of deionized water in a certain proportion, and then grind them in a fourth process at a temperature of 10℃ until the D50 particle size is 0.1μm and the solid content is 30wt% to obtain the second slurry.

[0029] S3. The first and second slurries are mixed and spray-dried to obtain the second precursor powder. Then, the powder is sintered at the fifth temperature of 810℃ for 6 hours and air-jet pulverized to obtain a high-capacity lithium iron phosphate cathode material with a D50 particle size of 0.8μm and a carbon content of 1.1wt%.

[0030] 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.

[0031] 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%.

[0032] Sintering at the first, second, third, fourth, and fifth temperatures is carried out under a protective gas, which in this embodiment is nitrogen.

[0033] Example 3 This embodiment provides a high-pressure, high-capacity lithium iron phosphate cathode material, the preparation method of which includes the following steps: S1, 3000g ferric phosphate, 788g ferric hydroxide, 1192.2g lithium phosphate, 10g lithium carbonate, 181.3g glucose, 164.8g polyethylene glycol, 41.3g titanium dioxide, and 5305g deionized water are mixed and ground at 30℃ until the D50 particle size is 0.7μm and the solid content is 50wt%. The mixture is then spray-dried to obtain the first precursor powder. The first portion of the first precursor powder is sintered at 830℃ for 5 hours using air jet milling to obtain an average primary particle size of 2000nm. The first intermediate is obtained by sintering the first precursor powder at a second temperature of 800℃ for 5 hours and then pulverizing it with airflow to obtain a second intermediate with an average primary particle size of 1200 nm. The third intermediate is obtained by sintering the first precursor powder at a third temperature of 740℃ for 5 hours and then pulverizing it with airflow to obtain a third intermediate with an average primary particle size of 600 nm. The fourth intermediate is obtained by sintering the first precursor powder at a fourth temperature of 600℃ for 5 hours and then pulverizing it with airflow to obtain a fourth intermediate with an average primary particle size of 150 nm.

[0034] S2. Mix 1600g of the first intermediate, 800g of the second intermediate, 80g of PVP, 48g of PEG, and 2400g of deionized water in a certain proportion, and then grind them in a third process at a temperature of 30℃ until the D50 particle size is 1.4μm and the solid content is 50wt%, to obtain the first slurry. Mix 400g of the third intermediate, 1200g of the fourth intermediate, 80g of PVP, 48g of PEG, and 1600g of deionized water in a certain proportion, and then grind them in a fourth process at a temperature of 30℃ until the D50 particle size is 0.5μm and the solid content is 50wt%, to obtain the second slurry.

[0035] S3. The first and second slurries are mixed and spray-dried to obtain the second precursor powder. Then, the powder is sintered at the fifth temperature of 750°C for 10 hours. The powder is then pulverized by airflow to obtain a high-capacity lithium iron phosphate cathode material with a D50 particle size of 1.2 μm and a carbon content of 1.5 wt%.

[0036] 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 200m². 2 / g.

[0037] 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%.

[0038] Sintering at the first, second, third, fourth, and fifth temperatures is carried out under a protective gas, which in this embodiment is nitrogen.

[0039] Comparative Example 1 The only difference between this comparative example and Example 1 is that, in S1, when preparing the first precursor powder, 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 precursor powder remains unchanged.

[0040] Comparative Example 2 The only difference between this comparative example and Example 1 is that 2400g of the first intermediate, 112g of PVP, and 3600g of deionized water were mixed in proportion, and then ground in a third process at a temperature of 20°C until the D50 particle size was 1.1μm and the solid content was 40wt%, thus obtaining the first slurry.

[0041] Comparative Example 3 The only difference between this comparative example and Example 1 is that 1600g of the fourth intermediate, 112g of PVP, and 2400g of deionized water were mixed in proportion, and then ground in a fourth process at a temperature of 20°C until the D50 particle size was 0.3μm and the solid content was 40wt%, thus obtaining the second slurry.

[0042] Comparative Example 4 The only difference between this comparative example and Example 1 is that the 112g PVP in S2 is replaced with 206.3g glucose.

[0043] The following tests were performed on Examples 1-3 and Comparative Examples 1-4: 1. Take 10kx scanning electron microscope images of the lithium iron phosphate cathode materials prepared in Examples 1-3 and Comparative Examples 1-4; 2. Weigh 1g of each of the lithium iron phosphate cathode materials prepared in Examples 1-3 and Comparative Examples 1-4 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 1-4 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 sheet. 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.

[0044] 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 are superior to the lithium iron phosphate cathode materials prepared in Comparative Examples 1-4 in all aspects of performance. Furthermore, the powder resistivity of the lithium iron phosphate cathode materials prepared in Examples 1-3 is significantly lower, and the powder compaction degree of the lithium iron phosphate cathode materials prepared in Examples 1-3 all reaches 2.7 g / cm³. 3 This meets the requirements of fifth-generation lithium iron phosphate materials for powder compaction.

[0045] 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 high-capacity lithium iron phosphate cathode material with high pressure and high density, characterized in that, Includes the following steps: Iron source, lithium source, phosphorus source, first carbon source, dopant, and deionized water are mixed in proportion, ground in the first stage, and spray-dried to obtain first precursor powder; the first portion of the first precursor powder is sintered at a first temperature and pulverized by airflow to obtain a first intermediate. The second part involves sintering the first precursor powder at a second temperature and then pulverizing it with airflow to obtain a second intermediate. The third part involves sintering the first precursor powder at a third temperature and then pulverizing it with airflow to obtain a third intermediate. The fourth part involves sintering the first precursor powder at a fourth temperature and then pulverizing it with airflow to obtain a fourth intermediate. The first intermediate, the second intermediate, the second carbon source, and deionized water are mixed in proportion and then subjected to a second grinding process to obtain the first slurry. The third intermediate, the fourth intermediate, the third carbon source, and deionized water are mixed in proportion and then subjected to a third grinding process to obtain a second slurry. The first and second slurries are mixed and spray-dried to obtain the second precursor powder, which is then sintered at a fifth temperature and pulverized by airflow to obtain the high-pressure, high-capacity lithium iron phosphate cathode material with a D50 particle size of 0.8~1.2μm. The first intermediate has an average primary particle size of 1500~2000nm; the second intermediate has an average primary particle size of 800~1200nm; the third intermediate has an average primary particle size of 300~600nm; and the fourth intermediate has an average primary particle size of 50~150nm. The iron source includes ferric phosphate and ferric hydroxide, wherein the ferric 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 lithium source is a battery-grade lithium source, including one or more of lithium carbonate, lithium phosphate, lithium hydroxide, and lithium dihydrogen phosphate; the phosphorus source is a battery-grade phosphorus source, including one or more of iron phosphate, lithium phosphate, lithium dihydrogen phosphate, phosphoric acid, and ammonium monohydrogen phosphate. The amount of lithium source added is determined according to the Li / Fe molar ratio of the high-pressure, high-capacity lithium iron phosphate cathode material being 1.01 to 1.05, and the amount of phosphorus source added is determined according to the Fe / P molar ratio of the high-pressure, high-capacity lithium iron phosphate cathode material being 0.965 to 0.

975.

3. The preparation method according to claim 1, characterized in that, The first carbon source includes one or more of glucose, PEG, citric acid, and sucrose, and the carbon content of the first precursor powder is 0.02~0.7wt%. The second and third carbon sources include one or more of polyethylene, PVP, PVDF, starch, PET, and polyamide; the carbon content of the high-pressure, high-capacity lithium iron phosphate cathode material is 1.1~1.5wt%.

4. The preparation method according to claim 1, characterized in that, The dopant includes one or more of titanium dioxide, ammonium metavanadate, niobium pentoxide, and manganese oxide; the content of the dopant element in the first precursor powder is 3000~6000ppm.

5. The preparation method according to claim 1, characterized in that, The first intermediate and the second intermediate are mixed in a ratio of 2~4:2~4, and the third intermediate and the fourth intermediate are mixed in a ratio of 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 and second 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 800~830℃ and the holding period to 5~11h; The second temperature sintering specifically includes: setting the temperature to 740~800℃ and holding the temperature for 5~11 hours; The third temperature sintering specifically includes: setting the temperature to 660~740℃ and holding the temperature for 5~11 hours; The fourth temperature sintering specifically includes: setting the temperature to 450~600℃ and holding the temperature for 5~11 hours; The fifth temperature sintering specifically includes setting the temperature to 750~810℃ 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 0.3–0.7 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 0.8–1.4 μm, and a solid content of 30–50 wt%. The third grinding process specifically includes: setting the temperature to 10-45℃, grinding to a D50 particle size of 0.1-0.5μm, and a solid content of 30-50wt%.

9. A high-pressure, high-capacity lithium iron phosphate cathode material, characterized in that, The high-pressure, high-capacity lithium iron phosphate cathode material is prepared by the preparation method described in 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 high-pressure, high-capacity lithium iron phosphate cathode material as described in claim 9.

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