Preparation method of high-compaction powder positive electrode material

Abstract

The invention provides a preparation method of a high-compaction powder positive electrode material, and belongs to the field of preparation of battery powder positive electrode materials. Comprising the following steps: (1) uniformly mixing raw materials corresponding to the high-compaction powder material; (2) pressing the mixture into a compact block; (3) sintering the block at high temperature to prepare a block precursor; (4) crushing the block precursor into a primary powder material; (5) carrying out secondary sintering on the primary powder material; and (6) polishing the secondary sintered material to prepare the target high-compaction powder material. The invention provides a preparation method of a high-compaction powder positive electrode material aiming at the defects of high porosity, insufficient particle stacking density, low particle sphericity degree, insufficient particle gradation gap filling and the like of the existing powder positive electrode material, and aims at solving the problems of insufficient stacking density, unobvious particle gradation effect, low compaction density and the like of powder positive electrode particles.

Description

Technical Field

[0001] This invention belongs to the field of powder materials, and particularly relates to a method for preparing a high-pressure compaction powder cathode material. Background Technology

[0002] Powder materials are widely used in various industries such as chemical, food, pharmaceutical, and building materials, with diverse applications. Currently, with the booming development of new energy cathode and anode materials in the chemical industry, the demand for high-compaction powder battery materials is also increasing. Especially as electric vehicles and energy storage power stations place increasingly higher demands on the energy density of new energy batteries, higher requirements are being placed on the compaction density of new energy cathode materials.

[0003] Currently, there are numerous methods for synthesizing cathode materials in the industry, including co-precipitation, high-temperature solid-state methods, sol-gel methods, and hydrothermal methods, each with its own advantages and disadvantages. However, as the industry's requirements for the compaction density of cathode materials become increasingly stringent, traditional preparation methods face drawbacks such as high porosity between powder cathode materials, insufficient particle packing density, poor particle sphericity, and insufficient particle gradation and gap filling. This results in cathode materials generally exhibiting disadvantages such as low compaction density and large specific surface area. Summary of the Invention

[0004] Based on the aforementioned shortcomings of current cathode materials, this invention provides a method for preparing high-compact powder cathode materials to solve problems such as insufficient packing density between powder cathode particles, insignificant particle gradation effect, and low compaction density.

[0005] A method for preparing a high-compact powder cathode material, the specific implementation scheme of which is as follows: (1) The raw material powder of the positive electrode material is added to the perfluorinated powder material and then ground until uniform. After spray drying, water is removed to obtain a mixture. (2) Press the mixture into compact blocks; (3) The bulk material is sintered at high temperature to prepare a bulk precursor; (4) Crush the bulk precursor into powder material; (5) The powder material is sand-milled, polished, spray-dried, and then sintered twice; (6) After crushing the secondary sintering material, a high-pressure compacted powder material is obtained.

[0006] The raw material powder for the cathode material mentioned in step (1) includes either lithium iron phosphate raw material powder or lithium manganese iron phosphate raw material powder. The raw material for the cathode material may also selectively contain dopants, which may be metallic or non-metallic elements.

[0007] Perfluorinated materials include any one or more combinations of perfluoropolyether siloxanes, polytetrafluoroethylene, perfluoroalkoxyalkane polymers, perfluoroethylene propylene, and perfluoroether rubber.

[0008] The amount of perfluorinated material added is 0.1-5 wt% of the raw material powder material for the cathode material.

[0009] The method for uniformly mixing raw materials in step (1) includes one or more of the following: physical grinding, dry mixing, sol-gel method, and co-precipitation method.

[0010] The pressing pressure in step (2) is 20-200 MPa, and the length, width and height of the pressed blank are (300-350) mm * (300-350) mm * (120-250) mm respectively.

[0011] The high-temperature sintering temperature in step (3) is 400-1000℃, and the sintering atmosphere is one or more of air, oxygen, and nitrogen.

[0012] In this invention, pressing followed by sintering enhances the contact force between powder particles, effectively improving heat transfer efficiency. Furthermore, perfluorinated materials, due to their excellent heat resistance and extremely low specific surface energy, effectively prevent excessive particle growth and severe adhesion after sintering during the formation of compact bulk materials. Through the combined effect of these two factors, the contradiction between excessive growth and irregular morphology during lithium iron phosphate sintering can be effectively controlled, significantly improving compaction density and balancing electrical properties.

[0013] The crushing method described in step (4) is one or more of the following: roller crusher, jaw crusher, extrusion, ball mill, and sand mill, to crush the particles to a size of 0.6-3.2 μm.

[0014] In step (5), a carbon source is selectively added, which includes one or more of glucose, cellulose, sucrose, polyethylene glycol, chitosan, and citric acid.

[0015] The polishing method described in step (5) is one or more of the following: air jet milling, ball milling, sand milling, and spray drying.

[0016] The secondary sintering temperature in step (5) is 400-1000℃, and the sintering atmosphere is one or both of nitrogen and argon.

[0017] The secondary sintering process in this invention has three main functions: first, it further reduces defects in the crystal structure of the material and improves the crystallinity of the cathode material; second, it simultaneously performs secondary carbon coating through secondary sintering; and third, it changes the morphology of the particles through secondary sintering and improves the sphericity of the particles.

[0018] The polishing method described in step (6) is one or more of the following: air jet milling, ball milling, sand milling, spray drying, coating, and sintering.

[0019] The present invention also provides the application of the high-compact powder material prepared by the high-compact powder material preparation method described above in the preparation of lithium iron phosphate and lithium manganese iron phosphate battery materials.

[0020] This invention effectively achieves the matching of large and small particles and the filling of gaps between particles in the cathode material through a continuous top-down synthesis process involving uniform mixing of raw materials, compaction, high-temperature sintering, crushing, secondary sintering, and polishing, thereby improving the compaction density of the powder cathode material. In the embodiment of this invention, the uniform mixing and compaction of raw materials first provide a uniform reaction environment for the subsequent high-temperature sintering reaction, ensuring the full generation of substances and the growth of the material towards bulk density. During the crushing of the bulk material, a matching of large and small particles is achieved, effectively realizing the gradation effect of the powder material. Further polishing of the powder particles after crushing further enhances the gradation effect and effectively improves the sphericity and surface smoothness of the powder particles, thereby further increasing the compaction density of the material. Attached Figure Description

[0021] Figure 1 This is a SEM image of lithium iron phosphate in Example 1 of the preparation of the high-pressure lithium iron phosphate powder cathode of the present invention.

[0022] Figure 2 This is a SEM image of lithium manganese iron phosphate in Example 4 of the preparation of the high-pressure lithium iron phosphate powder cathode of the present invention.

[0023] Figure 3 This is a SEM image of lithium iron phosphate in Comparative Example 1 during the preparation of the high-pressure lithium iron phosphate powder cathode of this invention.

[0024] Figure 4 This is a SEM image of lithium manganese iron phosphate in Comparative Example 2, used in the preparation of the high-pressure lithium iron phosphate powder cathode of this invention. Detailed Implementation

[0025] I. Preparation of High-Pressure Lithium Iron Phosphate Powder Cathode (1) Weigh a certain amount of the corresponding raw materials of lithium iron phosphate, such as iron phosphate, lithium carbonate, dopant, glucose, and perfluorinated powder materials, disperse them in pure water and then grind them. When the particle size of the mixed slurry meets the standard, spray dry to remove moisture and obtain a uniformly mixed synthetic raw material.

[0026] (2) Press the raw material obtained in step (1) into a block.

[0027] (3) The bulk material is sintered at high temperature to obtain lithium iron phosphate bulk material precursor.

[0028] (4) The sintered bulk material precursor is crushed to the target particle size by a jaw crusher, a double roll crusher, and an air jet mill.

[0029] (5) After the powdered material is dispersed in pure water containing glucose and PEG, it is sand-milled and polished until the target particle size is reached. Then, the sand-milled slurry is spray-dried and sintered again.

[0030] (6) After the material is sintered, it is subjected to air jet pulverization. After pulverization, high-pressure lithium iron phosphate powder cathode material is obtained.

[0031] Example 1 of high-pressure lithium iron phosphate powder cathode preparation Weigh out 500g of ferric phosphate, 123.31g of lithium carbonate, 18.13g of glucose, 4.5g of titanium dioxide, and 1.5g of polytetrafluoroethylene, disperse them in pure water, and mill them into a slurry with a particle size of 350 nm ≤ D. 50 Spray drying is performed when the nm is ≤450 nm.

[0032] The dried material was pressed into a compact at 50 MPa until the length, width and height were 340 mm * 340 mm * 185 mm.

[0033] The bulk material precursor was obtained by sintering the preform at 820°C for 10 hours under a nitrogen protective atmosphere.

[0034] The block material is then crushed sequentially through a jaw crusher, a double roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm.

[0035] The pulverized powder material was dispersed in pure water containing coating agents glucose and PEG and then ground until the slurry was ≤300nm. 50 After the particle size is ≤600 nm, it is spray-dried. The dried powder is sintered at 780℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium iron phosphate powder cathode material is obtained.

[0036] Example 2 of high-pressure lithium iron phosphate powder cathode preparation Weigh out 500g of ferrous oxalate, 301.25g of lithium dihydrogen phosphate, 18.13g of glucose, 4.5g of titanium dioxide, and 1.5g of perfluoroalkoxyalkane polymer, disperse them in anhydrous ethanol, and mill them until the particle size of the mixed slurry reaches 1μm≤D. 50 Spray drying is performed when the particle size is ≤3μm.

[0037] The dried material is pressed into a compact at 40MPa to a size of 350mm*350mm*180mm.

[0038] The bulk material precursor was obtained by sintering the preform at 820°C for 10 hours under a nitrogen protective atmosphere.

[0039] Then the block material is successively crushed by a jaw crusher, a double roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm; The pulverized powder material was dispersed in pure water containing coating agents glucose and PEG and then ground until the slurry was ≤300nm. 50 After the particle size is ≤600 nm, it is spray-dried. The dried powder is sintered at 780℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium iron phosphate powder cathode material is obtained.

[0040] Example 3 of high-pressure lithium iron phosphate powder cathode preparation Weigh out 500g of ferric oxide, 650.78g of lithium dihydrogen phosphate, 18.13g of glucose, 4.5g of titanium dioxide, and 1.5g of perfluoroethylene propylene. Disperse these components in pure water and mill them until the particle size of the mixed slurry reaches 450 nm ≤ D. 50 Spray drying is performed when the nm density is ≤600 nm.

[0041] The dried material is pressed into a compact at 50MPa to a size of 350mm*350mm*180mm.

[0042] The bulk material precursor was obtained by sintering the preform at 820°C for 10 hours under a nitrogen protective atmosphere.

[0043] Then the block material is successively crushed by a jaw crusher, a double roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm; The pulverized powder material was dispersed in pure water containing coating agents glucose and PEG and then ground until the slurry was ≤300nm. 50 After the particle size is ≤600 nm, it is spray-dried. The dried powder is sintered at 780℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium iron phosphate powder cathode material is obtained.

[0044] Comparative Example 1: Preparation of High-Pressure Lithium Iron Phosphate Powder Cathode Weigh out 250g of ferric oxide, 325.39g of lithium dihydrogen phosphate, 250g of ferric phosphate, 61.76g of lithium carbonate, 18.13g of glucose, and 4.5g of titanium dioxide, disperse them in pure water, and mill them into a slurry until the particle size of the mixture reaches 450 nm ≤ D. 50 Spray drying is performed when the nm density is ≤600 nm.

[0045] The dried material is pressed into a compact at 50MPa to a size of 350mm*350mm*180mm.

[0046] The bulk material precursor was obtained by sintering the preform at 820°C for 10 hours under a nitrogen protective atmosphere.

[0047] The block material is then crushed sequentially through a jaw crusher, a double roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm.

[0048] The pulverized powder material was dispersed in pure water containing coating agents glucose and PEG and then ground until the slurry was ≤300nm. 50 After the particle size is ≤600 nm, it is spray-dried. The dried powder is sintered at 780℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium iron phosphate powder cathode material is obtained. II. Preparation of High-Pressure Lithium Manganese Iron Phosphate Powder Cathode The preparation of high-density lithium manganese iron phosphate powder cathode material is basically the same as that of high-density lithium iron phosphate powder material, the difference lies in the corresponding raw materials and process control parameters.

[0049] Example 4 of high-pressure solid lithium manganese iron phosphate powder cathode preparation Weigh out 200g of ferric phosphate, 148.78g of manganese tetroxide, 122.81g of lithium carbonate, 224g of ammonium dihydrogen phosphate, 30.5g of glucose, 4.5g of titanium dioxide, and 2.5g of polytetrafluoroethylene. Disperse them in pure water and mill them until the particle size of the mixed slurry reaches 350 nm ≤ D. 50 Spray drying was performed at ≤400 nm. The dried material is pressed into a compact at 80MPa to a size of 350mm*350mm*180mm. The bulk material precursor was obtained by sintering the preform at 820°C for 10 hours under a nitrogen protective atmosphere. Then the block material is successively crushed by a jaw crusher, a double roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm; The pulverized powder material was dispersed in pure water containing coating agents glucose and PEG and then ground until a slurry with a particle size of 200 nm ≤ D was formed. 50 After the particle size is ≤500 nm, it is spray-dried. The dried powder is sintered at 760℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium manganese iron phosphate powder cathode material is obtained.

[0050] Example 5 of high-pressure solid lithium manganese iron phosphate powder cathode preparation Weigh out 200g of ferric phosphate, 148.78g of manganese tetroxide, 122.81g of lithium carbonate, 228.03g of phosphoric acid, 30.5g of glucose, 4.5g of titanium dioxide, and 2.5g of perfluoroether rubber. Disperse these components in pure water and mill them until the particle size of the mixed slurry reaches 350 nm ≤ D. 50 Spray drying was performed at ≤400 nm. The dried material was pressed into a compact at 80MPa to a size of 320mm*320mm*180mm. The preform was sintered at 820℃ for 10 h under a nitrogen protective atmosphere to obtain a bulk material precursor. The bulk material was then sequentially pulverized using a jaw crusher, a double-roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm. The pulverized powder was then dispersed in pure water containing coating agents glucose and PEG and ground into a slurry with a particle size D50 ≤ 3 μm. 50 After the particle size is ≤500 nm, it is spray-dried. The dried powder is sintered at 760℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium manganese iron phosphate powder cathode material is obtained.

[0051] Comparative Example 2: Preparation of High-Pressure Lithium Manganese Iron Phosphate Powder Cathode Weigh out 200g of ferric phosphate, 148.78g of manganese tetroxide, 202.60g of lithium dihydrogen phosphate, 50.09g of lithium carbonate, 30.5g of glucose, and 4.5g of titanium dioxide, disperse them in pure water, and mill them into a slurry until the particle size of the mixture reaches 350 nm ≤ D. 50 Spray drying was performed at ≤400 nm. The dried material is pressed into a compact at 50MPa to a size of 300mm*300mm*180mm; The bulk material precursor was obtained by sintering the preform at 820°C for 10 hours under a nitrogen protective atmosphere. Then the block material is successively crushed by a jaw crusher, a double roll crusher, and an air jet mill until the particle size D50 ≤ 3 μm; The pulverized powder material was dispersed in pure water containing coating agents glucose and PEG and then ground until a slurry with a particle size of 200 nm ≤ D was formed. 50 After the particle size is ≤500 nm, it is spray-dried. The dried powder is sintered at 760℃ for 8 hours in a nitrogen atmosphere and then subjected to air jet milling. After milling, high-pressure lithium manganese iron phosphate powder cathode material is obtained.

[0052]

[0053] 1. Testing conditions for compaction density: The prepared positive electrode powder material is uniformly poured into the mold of the powder compaction density tester. Pressure of 1, 2 and 3 tons is applied sequentially on the tablet press, and the pressure is held for 30 seconds after each application. The compaction density value under 3 tons is taken as the powder compaction density of the positive electrode material.

[0054] 2. Detection conditions for average sphericity: Common methods for calculating sphericity include the volume method and the diameter method. The diameter method defines particle sphericity as the ratio of the particle's perimeter-equivalent diameter to its area-equivalent diameter. The volume method defines particle sphericity as the ratio of the particle's surface area-equivalent diameter to its volume-equivalent diameter. This invention measures the microscopic morphology of particles using SEM, then obtains the particle perimeter and area through image analysis and soft statistics, and finally calculates the average sphericity of the particles using the diameter method.

[0055] 3. 1C Discharge Test Conditions: PVDF, Super-p, N-methylpyrrolidone, and the lithium manganese iron phosphate cathode material prepared in the examples and comparative examples were homogenized into a slurry. The mass ratio of lithium manganese iron phosphate cathode material, PVDF, and Super-p was 90:5:5, and the solid content of the slurry was 30%. The slurry was then coated, dried, and punched to obtain circular electrode sheets. Finally, the circular electrode sheets, separator, and lithium sheet were assembled into coin cells for testing in a glove box. The coin cells were charged and discharged within a voltage range of 2.0-3.75V (2.0~4.3V for lithium manganese iron phosphate).

Claims

1. A method for preparing a high-pressure compaction powder cathode material, characterized in that: The preparation method includes the following steps: (1) The raw material powder of the positive electrode material is added to the perfluorinated powder material and then ground until uniform. After spray drying, water is removed to obtain a mixture. (2) Press the mixture into compact blocks; (3) The bulk material is sintered at high temperature to prepare a bulk precursor; (4) Crush the bulk precursor into powder material; (5) The powder material is sand-milled, polished, spray-dried, and then sintered twice; (6) After crushing the secondary sintering material, a high-pressure compacted powder material is obtained.

2. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: The raw material powder of the cathode material mentioned in step (1) includes either lithium iron phosphate raw material powder or lithium manganese iron phosphate raw material powder.

3. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: Perfluorinated materials include any one or more combinations of polytetrafluoroethylene, perfluoroalkoxyalkylene polymers, perfluoroethylene propylene, and perfluoroether rubber.

4. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: The pressing pressure in step (2) is 20-200 MPa, and the volume of the pressed blank is (300-350) mm*(300-350) mm*(120-250) mm.

5. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: The high-temperature sintering temperature in step (3) is 400-1000℃, and the sintering atmosphere is one or both of nitrogen and argon.

6. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: The crushing method described in step (4) is one or more of the following: roller crusher, jaw crusher, extrusion, ball mill, and sand mill, to crush the particles to a size of 0.6-3.2 μm.

7. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: In step (5), a carbon source is selectively added, which includes one or more of glucose, cellulose, sucrose, polyethylene glycol, chitosan, and citric acid.

8. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: The polishing method described in step (5) is one or more of the following: air jet milling, ball milling, sand milling, and spray drying.

9. The method for preparing high-pressure compacted powder according to claim 1, characterized in that: The secondary sintering temperature is 400-1000℃, and the sintering atmosphere is one or both of nitrogen and argon.

10. The application of a high-compact powder material prepared by the method of any one of claims 1-9 in the preparation of lithium iron phosphate and lithium manganese iron phosphate cathode battery materials.

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