High-compaction lithium iron phosphate material and preparation method thereof
By preparing lithium iron phosphate sintered materials of three particle sizes and employing wet grinding and multiple sintering processes, the problems of insufficient compaction density and kinetic properties of lithium iron phosphate materials were solved, achieving high compaction density and good energy efficiency.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2026-02-06
- Publication Date
- 2026-04-21
AI Technical Summary
Existing technologies make it difficult to prepare a reasonable particle composition by changing the sintering temperature of lithium iron phosphate or by adding additives. This results in limited improvement in the compaction density of lithium iron phosphate materials, poor kinetic performance, and a lack of medium-sized particles between large and small particles, which affects the overall performance of the materials.
Three different precursors were used to prepare lithium iron phosphate sintered materials with three particle sizes. Through wet grinding, spray drying and multiple sintering, lithium iron phosphate materials with a reasonable ratio of large, medium and small particles were prepared. The particle size distribution effect was improved by utilizing the melt regeneration between different particles.
The compaction density of lithium iron phosphate material was increased to 2.733-2.788 g/cm3, achieving high compaction density and good kinetic performance. It also exhibits a good 1C 3.2V capacity ratio and demonstrates a higher material energy efficiency ratio.
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Figure CN121894636A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of battery materials technology, and in particular to a high-pressure lithium iron phosphate material and its preparation method. Background Technology
[0002] Lithium iron phosphate (LFP), as a cathode material for lithium-ion batteries, has been widely used in electric vehicles and large-scale energy storage due to its excellent safety, stable cycle performance, and low cost. However, its inherently low ionic and electronic conductivity and tap density limit further improvements in battery volumetric energy density. Increasing the tap density of the cathode material is one of the most direct and effective ways to improve battery volumetric energy density.
[0003] Existing technology involves mixing iron phosphate, lithium carbonate, carbon source, additives, and pure water, followed by coarse grinding, fine grinding, spray drying, high-temperature calcination, and pulverization to obtain large-particle lithium iron phosphate sintered material A. Then, it mixes iron phosphate, lithium carbonate, carbon source, additives, and pure water, followed by coarse grinding, fine grinding, spray drying, high-temperature calcination, and pulverization to obtain small-particle lithium iron phosphate sintered material B. Carbon source, additives, and pure water are added to materials A and B respectively, followed by coarse grinding and fine grinding to obtain two slurries of different particle sizes. These slurries are then mixed, spray-dried, calcined at high temperature, and pulverized to obtain a high-density lithium iron phosphate material. This approach uses iron phosphate with different Fe / P ratios as raw materials, prepares two types of lithium iron phosphate sintered materials with different particle sizes using different additives and sintering conditions, and then grinds and sinterstensibly according to a specific ratio to obtain a lithium iron phosphate material with a specific particle size distribution, achieving a high-density material. However, simply using different Fe / P iron phosphate particles prepared by varying sintering temperatures or adding additives makes it difficult to achieve a reasonable particle size distribution. Furthermore, conventional iron phosphate processes have the drawback of being unable to produce small, well-spherically shaped lithium iron phosphate particles, meaning this approach has limited effectiveness in improving compaction density. On the other hand, high-compact materials achieved using a combination of two particle sizes may lack sufficient kinetic performance, as they lack a medium-sized particle between large and small sizes to enhance the material's kinetic properties. Summary of the Invention
[0004] The purpose of this invention is to provide a high-pressure lithium iron phosphate material and its preparation method. Three precursors are used to prepare lithium iron phosphate sinter with three particle sizes. The slurry with different particle sizes is mixed in different mass ratios and then sintered and crushed to obtain a high-pressure lithium iron phosphate material with good energy efficiency.
[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 high-pressure lithium iron phosphate material, characterized by comprising the following steps: Preparation of large-particle lithium iron phosphate sintered material A: Weigh the first iron phosphate, lithium carbonate, carbon source, and additives, wet grind to the first particle size, spray dry to obtain the first spray-dried material; the first spray-dried material is sintered for the first time under a protective gas to obtain the large-particle lithium iron phosphate sintered material A; Preparation of intermediate particle lithium iron phosphate sintered material B: Weigh hydroxy iron phosphate, lithium phosphate, carbon source, and additives, wet grind to the second particle size, spray dry to obtain second spray-dried material; the second spray-dried material is sintered for the second time under protective gas to obtain the intermediate particle lithium iron phosphate sintered material B. Preparation of small-particle lithium iron phosphate sintered material C: Iron oxide red, second iron phosphate, lithium phosphate, third carbon source, and additives are weighed, wet-milled to the third particle size, and spray-dried to obtain the third spray-dried material; the third spray-dried material is sintered for the third time under a protective gas to obtain the small-particle lithium iron phosphate sintered material C. Preparation of the first, second, and third slurries: The large-particle lithium iron phosphate calcined material A is wet-mixed with the fourth carbon source and ground to obtain the first slurry; the intermediate-particle lithium iron phosphate calcined material B is wet-mixed with the fifth carbon source and ground to obtain the second slurry; the small-particle lithium iron phosphate calcined material C is wet-mixed with the sixth carbon source and ground to obtain the third slurry; Preparation of high-pressure lithium iron phosphate material: The first, second and third slurries are mixed in a mass ratio, spray dried, sintered, and crushed to obtain the high-pressure lithium iron phosphate material.
[0006] In some possible implementations, the molar ratio of lithium to iron (Li / Fe) in the large-particle lithium iron phosphate sintered material A is 1.01-1.07, the carbon content is 0.03-0.3%, and the doped metal cation content is 100-6000 ppm. In the intermediate particle lithium iron phosphate sintered feedstock B, the molar ratio of lithium to iron (Li / Fe) is 1.01-1.07, the carbon content is 0.03-0.3%, and the doped metal cation content is 100-6000 ppm. In the small-particle lithium iron phosphate sintered material C, the molar ratio of lithium to iron (Li / Fe) is 1.02-1.08, the carbon content is 0.05-0.3%, and the doped metal cation content is 4000-9000 ppm. In the first ferric phosphate, the molar ratio of iron to phosphorus (Fe / P) is 0.95-0.97; in the second ferric phosphate, the molar ratio of iron to phosphorus (Fe / P) is 0.95-0.985; and in the hydroxyferric phosphate, the molar ratio of iron to phosphorus (Fe / P) is 1.435-1.455. The first, second, third, fourth, fifth, and sixth carbon sources include one or more of glucose, sucrose, starch, fructose, maltose, cyclodextrin, citric acid, polyethylene glycol, polyvinyl alcohol, and polyglycerol; the first, second, and third additives include at least one or more of titanium dioxide, ammonium metavanadate, vanadium pentoxide, niobium pentoxide, anhydrous magnesium acetate, magnesium oxide, magnesium carbonate, nickel oxide, manganese dioxide, manganese trioxide, manganese tetroxide, and cerium dioxide.
[0007] In some possible implementations, the wet grinding to the first, second, and third particle sizes specifically includes: mixing with deionized water as a solvent, with a solid content of 30%-60%, stirring and dispersing, and then grinding to the first, second, and third particle sizes; the wet mixing and grinding specifically includes: mixing with deionized water as a solvent, with a solid content of 30%-60%, stirring and dispersing, and then grinding; theoretically, organic solvents such as ethanol or methanol can also be used as solvents for wet mixing, but their cost is higher and they are generally not used.
[0008] In some possible implementations, the first particle size specifically includes a D50 particle size of 0.4-0.9µm; the second particle size specifically includes a D50 particle size of 0.4-0.9µm; and the third particle size specifically includes a D50 particle size of 0.4-0.9µm. The first slurry has a D50 particle size of 1.2-2.0µm; the second slurry has a D50 particle size of 0.8-1.5µm; and the third slurry has a D50 particle size of 0.2-0.4µm. The D50 particle size of the high-pressure lithium iron phosphate material is 0.6-1.5µm.
[0009] In some possible implementations, the first sintering and crushing specifically includes: setting the first sintering temperature to 770-830℃ and the first sintering time to 3-10h; The second sintering specifically includes: setting the second sintering temperature to 700-770℃ and the second sintering time to 3-10h; The third sintering specifically includes: setting the third sintering temperature to 450-680℃ and the third sintering time to 3-10h; The fourth sintering specifically includes setting the fourth sintering temperature to 730-820℃ and the fourth sintering time to 3-10h.
[0010] In some possible implementations, the total amount of the fourth, fifth, and sixth carbon sources added results in a carbon content of 1.2-1.8% in the high-pressure lithium iron phosphate material.
[0011] In some possible implementations, the mixing of the first, second, and third slurries by mass ratio specifically includes: the mass ratio of lithium iron phosphate sintered materials A, B, and C in the first, second, and third slurries is (4-7):(1-3):(2-5).
[0012] In some possible implementations, the spray drying specifically includes setting the inlet air temperature to 200-280°C and the outlet air temperature to 90-120°C.
[0013] In some possible implementations, the protective gas is at least one of nitrogen or argon.
[0014] Secondly, the present invention also provides a high-pressure lithium iron phosphate material, prepared based on the preparation method described in any one of the first aspects. The high-pressure lithium iron phosphate material and its preparation method provided by this invention have the following advantages compared with the prior art: 1. High-compaction lithium iron phosphate was prepared by grading lithium iron phosphate with three different particle sizes. The resulting lithium iron phosphate particle combination is more reasonable, which can effectively reduce the number of extremely large particles in the material and improve the kinetic performance of the material. Medium-sized lithium iron phosphate particles are between large and small lithium iron phosphate particles, which can alleviate the gap between large and small particles. Small-sized lithium iron phosphate particles can effectively fill the gaps between particles and further improve the compaction of the material. At the same time, medium and small particles are also beneficial to the improvement of the electrochemical performance of the material. 2. Three particle sizes of lithium iron phosphate were prepared using various precursor properties. Experiments showed that low Fe / P iron phosphate (0.95-0.97) was more likely to form large particles with better sphericity during sintering; hydroxy iron phosphate was easily sintered into medium-sized particles at suitable temperatures; and small-particle lithium iron phosphate with better roundness was prepared at low temperatures using iron oxide red and iron phosphate as a mixed iron source, overcoming the defect of conventional iron phosphate processes that are difficult to prepare small-particle lithium iron phosphate with good sphericity. Furthermore, after secondary grinding and sintering, the lithium iron phosphate particles further grew, and the lithium iron phosphate sintered material of different sizes underwent melting and regeneration, improving the particle size distribution. Therefore, the lithium iron phosphate material prepared using this process not only has a high compaction density of 2.733-2.788 g / cm³, but also exhibits other desirable properties. 3 It also has good dynamic performance (1C 3.2V capacity ratio). Attached Figure Description
[0015] Figure 1 Here is a SEM image of the finished product from Example 1; Figure 2 SEM image of the finished product in Comparative Example 2; Figure 3 This is a SEM image of the finished product in Comparative Example 3. Detailed Implementation
[0016] 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.
[0017] Example 1 This embodiment provides a high-pressure lithium iron phosphate material, the preparation method of which includes the following steps: Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 160g of glucose (first carbon source), 50g of polyethylene glycol, and 15g of titanium dioxide (first additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to the first particle size using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the first spray-dried material. Perform the first sintering under a nitrogen atmosphere, setting the first sintering temperature to 810℃ and the first sintering time to 8 hours to obtain large-particle lithium iron phosphate sintered material A.
[0018] Weigh out 5000g of hydroxyferric phosphate, 1517g of lithium phosphate, 201.4g of glucose (second carbon source), 57.5g of polyethylene glycol, and 16.4g of titanium dioxide (second additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to the second particle size using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 95℃ to obtain the second spray-dried material. Under a nitrogen atmosphere, perform a second sintering, setting the second sintering temperature to 750℃ and the second sintering time to 8 hours to obtain intermediate-particle lithium iron phosphate sintered material B.
[0019] Weigh out 1348.9g of iron oxide red, 5000g of iron phosphate, 1986.7g of lithium phosphate, 375g of glucose and 75g of polyethylene glycol as the third carbon source, and 97.5g of titanium dioxide as the third additive. Use 12000g of deionized water as a solvent, stir and disperse for 30 minutes, then grind to the third particle size using a sand mill, spray dry, set the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the third spray-dried material. Under a nitrogen atmosphere, perform a third sintering, set the third sintering temperature to 550℃ and the third sintering time to 8 hours to obtain small-particle lithium iron phosphate sintered material C.
[0020] Weigh 3000g of large-particle lithium iron phosphate sintered material A, 135g of glucose and 135g of polyethylene glycol (the fourth carbon source), and use 4000g of deionized water as a solvent. After stirring and dispersing for 30 minutes, grind the mixture using a sand mill to obtain the first slurry. Weigh 3000g of medium-particle lithium iron phosphate sintered material B, 135g of glucose and 135g of polyethylene glycol (the fifth carbon source), and use 4000g of deionized water as a solvent. After stirring and dispersing for 30 minutes, grind the mixture using a sand mill to obtain the second slurry. Weigh 3000g of small-particle lithium iron phosphate sintered material C, 135g of glucose and 135g of polyethylene glycol (the sixth carbon source), and use 4000g of deionized water as a solvent. After stirring and dispersing for 30 minutes, grind the mixture using a sand mill to obtain the third slurry.
[0021] The first, second, and third slurries are mixed according to the mass ratio of lithium iron phosphate in the first, second, and third slurries of 4:1.5:4.5. After spray drying, the inlet air temperature is set to 240℃ and the outlet air temperature is set to 100℃. Under a nitrogen atmosphere, a fourth sintering is carried out, with the fourth sintering temperature set to 780℃ and the fourth sintering time set to 6 hours. After crushing, high-pressure compacted lithium iron phosphate material is obtained.
[0022] In this embodiment, the first particle size specifically includes a D50 particle size of 0.7µm; the second particle size specifically includes a D50 particle size of 0.7µm; and the third particle size specifically includes a D50 particle size of 0.8µm.
[0023] The D50 particle size of the first slurry is 1.8µm; the D50 particle size of the second slurry is 0.8µm; the D50 particle size of the third slurry is 0.25µm; and the D50 particle size of the high-pressure lithium iron phosphate material is 1.2µm.
[0024] In other embodiments, the first, second, third, fourth, fifth, and sixth carbon sources may include one or more of sucrose, starch, fructose, maltose, cyclodextrin, citric acid, polyvinyl alcohol, and polyglycerol; the first, second, and third additives may include at least one or more of vanadium pentoxide, anhydrous magnesium acetate, magnesium oxide, magnesium carbonate, nickel oxide, manganese dioxide, manganese trioxide, manganese tetroxide, and cerium dioxide.
[0025] In other embodiments, the first particle size may include: a D50 particle size of 0.4 or 0.9 µm; the second particle size may include: a D50 particle size of 0.4 or 0.9 µm; the third particle size may include: a D50 particle size of 0.4 or 0.9 µm; the D50 particle size of the first slurry may be 1.2 or 2.0 µm; the D50 particle size of the second slurry may be 1.0 or 1.5 µm; the D50 particle size of the third slurry may be 0.2 or 0.4 µm; and the D50 particle size of the high-pressure lithium iron phosphate material may be 0.6 or 1.5 µm.
[0026] In other embodiments, the first sintering temperature can be set to 770 or 830°C, the first sintering time to 3 or 10 hours, the second sintering temperature to 700 or 770°C, the second sintering time to 3 or 10 hours, the third sintering temperature to 450 or 680°C, the third sintering time to 3 or 10 hours, and the fourth sintering temperature to 730 or 820°C, the fourth sintering time to 3 or 10 hours.
[0027] In other embodiments, the inlet air temperature can be set to 200 or 280°C, the outlet air temperature to 90 or 120°C, and the protective gas can be argon.
[0028] Example 2 Weigh out 5000g of iron phosphate, 1265.9g of lithium carbonate, 165g of glucose (first carbon source), 50g of polyethylene glycol, and 20g of titanium dioxide (first additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to the first particle size using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the first spray-dried material. Perform the first sintering under a nitrogen atmosphere, setting the first sintering temperature to 820℃ and the first sintering time to 7 hours to obtain large-particle lithium iron phosphate sintered material A.
[0029] Weigh out 5000g of hydroxyferric phosphate, 1509.6g of lithium phosphate, 190g of glucose (second carbon source), 57.5g of polyethylene glycol, and 23g of titanium dioxide (second additive). Use 8300g of deionized water as solvent, stir and disperse for 30 minutes, then grind to the second particle size using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the second spray-dried material. Perform a second sintering under a nitrogen atmosphere, setting the second sintering temperature to 770℃ and the second sintering time to 8 hours to obtain intermediate-particle lithium iron phosphate sintered material B.
[0030] Weigh out 1348.9g of iron oxide red, 5000g of iron phosphate, 1996.3g of lithium phosphate, 375g of glucose and 75g of polyethylene glycol as the third carbon source, and 105g of titanium dioxide as the third additive. Use 12000g of deionized water as a solvent, stir and disperse for 30 minutes, then grind to the third particle size using a sand mill, spray dry, set the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the third spray-dried material. Under a nitrogen atmosphere, perform a third sintering, set the third sintering temperature to 550℃ and the third sintering time to 8 hours to obtain small-particle lithium iron phosphate sintered material C.
[0031] Weigh 3000g of large-particle lithium iron phosphate sintered material A, 90g of glucose and 270g of polyethylene glycol as the fourth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30 minutes, and then grind through a sand mill to obtain the first slurry; weigh 3000g of medium-particle lithium iron phosphate sintered material B, 90g of glucose and 270g of polyethylene glycol as the fifth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30 minutes, and then grind through a sand mill to obtain the second slurry; weigh 3000g of small-particle lithium iron phosphate sintered material C, 90g of glucose and 270g of polyethylene glycol as the sixth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30 minutes, and then grind through a sand mill to obtain the third slurry.
[0032] The first, second, and third slurries are mixed according to the mass ratio of lithium iron phosphate in the first, second, and third slurries of 4:2:4. After spray drying, the inlet air temperature is set to 240℃ and the outlet air temperature is set to 100℃. Under a nitrogen atmosphere, a fourth sintering is carried out, with the fourth sintering temperature set to 780℃ and the fourth sintering time set to 6 hours. After crushing, high-pressure compacted lithium iron phosphate material is obtained.
[0033] In this embodiment, the first particle size specifically includes a D50 particle size of 0.75µm; the second particle size specifically includes a D50 particle size of 0.65µm; and the third particle size specifically includes a D50 particle size of 0.7µm.
[0034] The D50 particle size of the first slurry is 1.8µm; the D50 particle size of the second slurry is 0.8µm; the D50 particle size of the third slurry is 0.25µm; and the D50 particle size of the high-pressure lithium iron phosphate material is 1.15µm.
[0035] Example 3 Weigh 5000g of iron phosphate, 1259.7.9g of lithium carbonate, 175g of glucose as the first carbon source, and 15g of ammonium metavanadate as the first additive. Use 8600g of deionized water as a solvent, stir and disperse for 30 minutes, then grind to the first particle size using a sand mill, spray dry, set the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the first spray-dried material. Under a nitrogen atmosphere, perform the first sintering, set the first sintering temperature to 800℃ and the first sintering time to 8h to obtain large-particle lithium iron phosphate sintered material A.
[0036] Weigh out 5000g of hydroxyferric phosphate, 1524g of lithium phosphate, 190g of glucose (second carbon source), 57.5g of polyethylene glycol, 28.8g of titanium dioxide (second additive), and 4.6g of niobium pentoxide. Use 8300g of deionized water as solvent, stir and disperse for 30 minutes, then grind to the second particle size using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the second spray-dried material. Perform a second sintering under a nitrogen atmosphere, setting the second sintering temperature to 750℃ and the second sintering time to 8 hours to obtain intermediate-particle lithium iron phosphate sintered material B.
[0037] Weigh out 1348.9g of iron oxide red, 5000g of iron phosphate, 1986.7g of lithium phosphate, 375g of glucose and 75g of polyethylene glycol as the third carbon source, and 105g of titanium dioxide as the third additive. Use 12000g of deionized water as a solvent, stir and disperse for 30 minutes, then grind to the third particle size using a sand mill, spray dry, set the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the third spray-dried material. Under a nitrogen atmosphere, perform a third sintering, set the third sintering temperature to 600℃ and the third sintering time to 8 hours to obtain small-particle lithium iron phosphate sintered material C.
[0038] Weigh 3000g of large-particle lithium iron phosphate sintered material A, 120g of glucose and 150g of polyethylene glycol (the fourth carbon source), and use 4000g of deionized water as a solvent. After stirring and dispersing for 30 minutes, grind the mixture using a sand mill to obtain the first slurry. Weigh 3000g of medium-particle lithium iron phosphate sintered material B, 120g of glucose and 150g of polyethylene glycol (the fifth carbon source), and use 4000g of deionized water as a solvent. After stirring and dispersing for 30 minutes, grind the mixture using a sand mill to obtain the second slurry. Weigh 3000g of small-particle lithium iron phosphate sintered material C, 120g of glucose and 150g of polyethylene glycol (the sixth carbon source), and use 4000g of deionized water as a solvent. After stirring and dispersing for 30 minutes, grind the mixture using a sand mill to obtain the third slurry.
[0039] The first, second, and third slurries are mixed according to the mass ratio of lithium iron phosphate in the first, second, and third slurries of 5:1:4. After spray drying, the inlet air temperature is set to 240℃ and the outlet air temperature is set to 100℃. Under a nitrogen atmosphere, a fourth sintering is carried out, with the fourth sintering temperature set to 770℃ and the fourth sintering time set to 7h. After crushing, high-pressure compacted lithium iron phosphate material is obtained.
[0040] In this embodiment, the first particle size specifically includes a D50 particle size of 0.7µm; the second particle size specifically includes a D50 particle size of 0.7µm; and the third particle size specifically includes a D50 particle size of 0.7µm.
[0041] The D50 particle size of the first slurry is 1.8µm; the D50 particle size of the second slurry is 0.8µm; the D50 particle size of the third slurry is 0.27µm; and the D50 particle size of the high-pressure lithium iron phosphate material is 1.1µm.
[0042] Example 4 The only difference between this embodiment and Embodiment 1 is that... 3000g of large-particle lithium iron phosphate sintered material A, 1125g of intermediate-particle lithium iron phosphate sintered material B, 165g of glucose and 165g of polyethylene glycol (fourth carbon source) were stirred and dispersed in 8000g of deionized water for 30 minutes, and then ground in a sand mill to obtain the first slurry. 3000g of small-particle lithium iron phosphate sintered material C, 120g of glucose and 120g of polyethylene glycol (fifth carbon source) were stirred and dispersed in 4000g of deionized water for 30 minutes, and then ground in a sand mill to obtain the second slurry.
[0043] The first and second slurries are mixed according to a lithium iron phosphate mass ratio of 4:1.5:4.5.
[0044] In this embodiment, the D50 particle size of the first slurry is 1.6µm; the D50 particle size of the second slurry is 0.25µm; and the D50 particle size of the high-pressure lithium iron phosphate material is 1.3µm.
[0045] Comparative Example 1 Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 160g of glucose (first carbon source), 50g of polyethylene glycol, and 15g of titanium dioxide (first additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.7µm using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the first spray-dried material. Perform the first sintering under a nitrogen atmosphere, setting the first sintering temperature to 810℃ and the first sintering time to 8h to obtain large-particle lithium iron phosphate sintered material A.
[0046] Weigh out 1348.9g of iron oxide red, 5000g of iron phosphate, 1986.7g of lithium phosphate, 375g of glucose and 75g of polyethylene glycol as a second carbon source, and 97.5g of titanium dioxide as a second additive. Use 12000g of deionized water as a solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.8µm using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the second spray-dried material. Under a nitrogen atmosphere, perform a second sintering, setting the second sintering temperature to 550℃ and the second sintering time to 8 hours to obtain small-particle lithium iron phosphate sintered material B.
[0047] Weigh 3000g of large-particle lithium iron phosphate sintered material A, 135g of glucose and 135g of polyethylene glycol as the third carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, and then grind through a sand mill to obtain the first slurry with a D50 particle size of 1.8µm; weigh 3000g of small-particle lithium iron phosphate sintered material B, 135g of glucose and 135g of polyethylene glycol as the fourth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, and then grind through a sand mill to obtain the second slurry with a D50 particle size of 0.26µm.
[0048] The first and second slurries were mixed according to a lithium iron phosphate mass ratio of 6:4. After spray drying, the inlet air temperature was set to 240℃ and the outlet air temperature to 100℃. Under a nitrogen atmosphere, a fourth sintering was carried out at a temperature of 780℃ for 6 hours. The mixture was then crushed to obtain high-pressure compacted lithium iron phosphate material with a D50 particle size of 1.25µm.
[0049] Comparative Example 2 Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 160g of glucose (first carbon source), 50g of polyethylene glycol, and 15g of titanium dioxide (first additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.7µm using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the first spray-dried material. Perform the first sintering under a nitrogen atmosphere, setting the first sintering temperature to 810℃ and the first sintering time to 8h to obtain large-particle lithium iron phosphate sintered material A.
[0050] Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 155g of glucose (second carbon source), 50g of polyethylene glycol, and 65g of titanium dioxide (second additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.7µm using a sand mill. Spray dry the mixture, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the second spray-dried material. Under a nitrogen atmosphere, perform a second sintering, setting the second sintering temperature to 600℃ and the second sintering time to 8 hours to obtain small-particle lithium iron phosphate sintered material B.
[0051] Weigh 3000g of large-particle lithium iron phosphate calcined material A, 135g of glucose and 135g of polyethylene glycol as the third carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, and then grind through a sand mill to obtain the first slurry with a D50 particle size of 1.6µm; weigh 3000g of small-particle lithium iron phosphate calcined material B, 135g of glucose and 135g of polyethylene glycol as the fourth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, and then grind through a sand mill to obtain the second slurry with a D50 particle size of 0.28µm.
[0052] The first and second slurries were mixed according to a lithium iron phosphate mass ratio of 7:3. After spray drying, the inlet air temperature was set to 240℃ and the outlet air temperature to 100℃. Under a nitrogen atmosphere, a fourth sintering was carried out at a temperature of 790℃ for 6 hours. The mixture was then crushed to obtain high-pressure compacted lithium iron phosphate material with a D50 particle size of 1.32µm.
[0053] Comparative Example 3 Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 160g of glucose (first carbon source), 50g of polyethylene glycol, and 15g of titanium dioxide (first additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.7µm using a sand mill. Spray dry the material, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the first spray-dried material. Perform the first sintering under a nitrogen atmosphere, setting the first sintering temperature to 810℃ and the first sintering time to 8h to obtain large-particle lithium iron phosphate sintered material A.
[0054] Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 200g of glucose (second carbon source), 50g of polyethylene glycol, and 20g of titanium dioxide (second additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.7µm using a sand mill. Spray dry the mixture, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the second spray-dried material. Under a nitrogen atmosphere, perform a second sintering, setting the second sintering temperature to 730℃ and the second sintering time to 8 hours to obtain large-particle lithium iron phosphate sintered material B.
[0055] Weigh out 5000g of iron phosphate, 1257.3g of lithium carbonate, 155g of glucose (third carbon source), 50g of polyethylene glycol, and 65g of titanium dioxide (third additive). Use 8600g of deionized water as solvent, stir and disperse for 30 minutes, then grind to a D50 particle size of 0.7µm using a sand mill. Spray dry the mixture, setting the inlet air temperature to 240℃ and the outlet air temperature to 100℃ to obtain the third spray-dried material. Under a nitrogen atmosphere, perform a third sintering, setting the third sintering temperature to 600℃ and the third sintering time to 8 hours to obtain small-particle lithium iron phosphate sintered material C.
[0056] Weigh 3000g of large-particle lithium iron phosphate sintered material A, 90g of glucose and 270g of polyethylene glycol as the third carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, then grind through a sand mill to obtain the first slurry with a D50 particle size of 1.8µm; weigh 3000g of large-particle lithium iron phosphate sintered material B, 90g of glucose and 270g of polyethylene glycol as the fourth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, then grind through a sand mill to obtain the second slurry with a D50 particle size of 0.8µm; weigh 3000g of small-particle lithium iron phosphate sintered material C, 90g of glucose and 270g of polyethylene glycol as the fourth carbon source, use 4000g of deionized water as the solvent, stir and disperse for 30min, then grind through a sand mill to obtain the third slurry with a D50 particle size of 0.25µm.
[0057] The first, second, and third slurries were mixed according to a lithium iron phosphate mass ratio of 4:2:4. After spray drying, the inlet air temperature was set to 240℃ and the outlet air temperature to 100℃. Under a nitrogen atmosphere, a fourth sintering was carried out at a temperature of 780℃ for 6 hours. The mixture was then crushed to obtain high-pressure compacted lithium iron phosphate material with a D50 particle size of 1.25µm.
[0058] The compaction density, 0.1C / 1C discharge specific capacity, and 1C 3.2V capacity ratio of Examples 1-4 and Comparative Examples 1-3 were tested using the following methods: According to GB / T 30835-2014 "Carbon Composite Lithium Iron Phosphate Cathode Material for Lithium-ion Batteries", relevant physicochemical and electrochemical properties were tested, including the fabrication of coin cells (the mass ratio of active material, conductive agent and binder is 90:5:5, and the charge and discharge voltage range is 2.0-3.75V).
[0059] The results are shown in Table 1: contrast Figure 1-3 The lithium iron phosphate finished product prepared by using three precursors to prepare three particle sizes has significant advantages in controlling the large lithium iron phosphate particles and the roundness of the small lithium iron phosphate particles, which is reflected in the higher powder compaction density. Secondly, the addition of intermediate particles significantly improves the energy efficiency ratio of lithium iron phosphate materials (1C 3.2V capacity ratio), demonstrating the advantages of this scheme in material compaction density and energy efficiency ratio.
[0060] 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-pressure lithium iron phosphate material, characterized in that, Includes the following steps: Preparation of large-particle lithium iron phosphate sintered material A: Weigh the first iron phosphate, lithium carbonate, carbon source, and additives, wet grind to the first particle size, spray dry to obtain the first spray-dried material; the first spray-dried material is sintered for the first time under a protective gas to obtain the large-particle lithium iron phosphate sintered material A; Preparation of intermediate particle lithium iron phosphate sintered material B: Weigh hydroxy iron phosphate, lithium phosphate, carbon source, and additives, wet grind to the second particle size, spray dry to obtain second spray-dried material; the second spray-dried material is sintered for the second time under protective gas to obtain the intermediate particle lithium iron phosphate sintered material B. Preparation of small-particle lithium iron phosphate sintered material C: Iron oxide red, second iron phosphate, lithium phosphate, third carbon source, and additives are weighed, wet-milled to the third particle size, and spray-dried to obtain the third spray-dried material; the third spray-dried material is sintered for the third time under a protective gas to obtain the small-particle lithium iron phosphate sintered material C. Preparation of the first, second, and third slurries: The large-particle lithium iron phosphate calcined material A is wet-mixed with the fourth carbon source and ground to obtain the first slurry; the intermediate-particle lithium iron phosphate calcined material B is wet-mixed with the fifth carbon source and ground to obtain the second slurry; the small-particle lithium iron phosphate calcined material C is wet-mixed with the sixth carbon source and ground to obtain the third slurry; Preparation of high-pressure lithium iron phosphate material: The first, second and third slurries are mixed in a mass ratio, spray dried, sintered for the fourth time, and crushed to obtain the high-pressure lithium iron phosphate material.
2. The preparation method according to claim 1, characterized in that, In the large-particle lithium iron phosphate sintered material A, the molar ratio of lithium to iron (Li / Fe) is 1.01-1.07, the carbon content is 0.03-0.3%, and the doped metal cation content is 100-6000 ppm. In the intermediate particle lithium iron phosphate sintered feedstock B, the molar ratio of lithium to iron (Li / Fe) is 1.01-1.07, the carbon content is 0.03-0.3%, and the doped metal cation content is 100-6000 ppm. In the small-particle lithium iron phosphate sintered material C, the molar ratio of lithium to iron (Li / Fe) is 1.02-1.08, the carbon content is 0.05-0.3%, and the doped metal cation content is 4000-9000 ppm. In the first ferric phosphate, the molar ratio of iron to phosphorus (Fe / P) is 0.95-0.97; in the second ferric phosphate, the molar ratio of iron to phosphorus (Fe / P) is 0.95-0.985; and in the hydroxyferric phosphate, the molar ratio of iron to phosphorus (Fe / P) is 1.435-1.
455. The first, second, third, fourth, fifth, and sixth carbon sources include one or more of glucose, sucrose, starch, fructose, maltose, cyclodextrin, citric acid, polyethylene glycol, polyvinyl alcohol, and polyglycerol; the first, second, and third additives include at least one or more of titanium dioxide, ammonium metavanadate, vanadium pentoxide, niobium pentoxide, anhydrous magnesium acetate, magnesium oxide, magnesium carbonate, nickel oxide, manganese dioxide, manganese trioxide, manganese tetroxide, and cerium dioxide.
3. The preparation method according to claim 1, characterized in that, The wet grinding to the first, second, and third particle sizes specifically includes: using deionized water as a solvent, mixing with a solid content of 30%-60%, stirring and dispersing, and then grinding to the first, second, and third particle sizes; the wet mixing and grinding specifically includes: using deionized water as a solvent, mixing with a solid content of 30%-60%, stirring and dispersing, and then grinding.
4. The preparation method according to claim 1, characterized in that, The first particle size specifically includes a D50 particle size of 0.4-0.9µm; the second particle size specifically includes a D50 particle size of 0.4-0.9µm; the third particle size specifically includes a D50 particle size of 0.4-0.9µm. The first slurry has a D50 particle size of 1.2-2.0µm; the second slurry has a D50 particle size of 0.8-1.5µm; and the third slurry has a D50 particle size of 0.2-0.4µm. The D50 particle size of the high-pressure lithium iron phosphate material is 0.6-1.5µm.
5. The preparation method according to claim 1, characterized in that, The first sintering process specifically includes setting the first sintering temperature to 770-830℃ and the first sintering time to 3-10h. The second sintering specifically includes: setting the second sintering temperature to 700-770℃ and the second sintering time to 3-10h; The third sintering specifically includes: setting the third sintering temperature to 450-680℃ and the third sintering time to 3-10h; The fourth sintering specifically includes setting the fourth sintering temperature to 730-820℃ and the fourth sintering time to 3-10h.
6. The preparation method according to claim 1, characterized in that, The total addition of the fourth, fifth, and sixth carbon sources results in a carbon content of 1.2-1.8% in the high-pressure lithium iron phosphate material.
7. The preparation method according to claim 1, characterized in that, The mixing of the first, second, and third slurries by mass ratio specifically includes the following: the mass ratio of lithium iron phosphate sintered material A, B, and C in the first, second, and third slurries is (4-7):(1-3):(2-5).
8. The preparation method according to claim 1, characterized in that, The spray drying specifically includes setting the inlet air temperature to 200-280℃ and the outlet air temperature to 90-120℃.
9. The preparation method according to claim 1, characterized in that, The protective gas is at least one of nitrogen or argon.
10. A high-pressure lithium iron phosphate material, characterized in that, Prepared according to the preparation method according to any one of claims 1-9.