Preparation method and application of high-compaction lithium iron phosphate
By controlling the grinding particle size and additives, nano- and micron-sized spherical particles are prepared to form a densely packed structure, solving the problem of low compaction density of lithium iron phosphate powder and achieving high compaction density and low-cost production.
Patent Information
- Application Number
- CN202511283455.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-09
- Publication Date
- 2025-12-12
AI Technical Summary
In existing technologies, it is difficult to further improve the compaction density of lithium iron phosphate powder, high-temperature sintering is prone to generating impurity phases and has high cost, and the mixing and gradation process is complex and unstable.
By controlling the grinding particle size and adding different carbon sources and dopants, nano- and micron-sized spherical particles are prepared to form a three-dimensional conductive network. The particle size distribution is optimized by spray drying and sintering processes to form a densely packed structure.
The increased compaction density of lithium iron phosphate reduced production costs and energy consumption, while also improving material uniformity and stability, thus meeting the requirements of green manufacturing.
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Figure CN121107380A_ABST
Abstract
Description
Technical Field
[0001] This invention relates to the field of lithium-ion battery technology, specifically to a high-pressure lithium iron phosphate preparation method. Background Technology
[0002] In the field of lithium-ion batteries, with the booming development of electric vehicle technology with long driving range and the demand for high-performance energy storage, extremely stringent requirements are placed on the volumetric and mass energy density of lithium battery cathode materials. Lithium iron phosphate has become a highly promising cathode material choice due to its many significant advantages such as high safety, long cycle life, environmental friendliness and abundant resources.
[0003] However, its specific capacity has been approaching its theoretical limit after years of technological breakthroughs, and the room for improvement is extremely limited. Under these circumstances, continuously improving the compaction density of the material has become a key and effective way to further improve the volumetric energy density of lithium iron phosphate.
[0004] In the current industry, various technical strategies are adopted to improve the compaction density of lithium iron phosphate. Some companies try to increase the sintering temperature to promote particle melting, intending to improve the compaction density of the material powder. However, during the high-temperature sintering process, the material is very easy to react with impurities in the environment, generating impurity phases that are not conducive to electrochemical reactions, directly causing loss of electrical performance.
[0005] Meanwhile, the high-temperature process significantly increases production energy consumption, leading to a significant increase in production costs. This high-investment, low-return approach makes it difficult to achieve large-scale industrial application. Some companies choose to sinter lithium iron phosphate particles of different sizes separately and then mix them to achieve particle size distribution. This is the most direct method for preparing high-compact lithium iron phosphate. However, this method has limited ways to form large-particle lithium iron phosphate, and there is also the problem of poor mixing uniformity during the mixing process, resulting in unstable compaction density of the final product and significant differences in quality between batches.
[0006] Some companies have tried to mix and grade two different particle sizes of slurry in the hope of improving compaction density by optimizing particle distribution. However, this method requires additional equipment for slurry preparation and mixing, involves complex process parameter control, is cumbersome, and requires a large investment in equipment procurement and process debugging in the early stage. Summary of the Invention
[0007] The purpose of this invention is to provide a method for preparing high-compaction lithium iron phosphate and its application, which solves the technical problem that the powder compaction density in the preparation of lithium iron phosphate needs to be further improved in the prior art.
[0008] The objective of this invention can be achieved through the following technical solution: a method for preparing high-pressure lithium iron phosphate, comprising the following steps:
[0009] S1. Add iron source, phosphorus source, lithium source, first carbon source, second carbon source, and dopant to deionized water and mix. Disperse by ultrasonication for 20-30 minutes, then transfer to a sand mill and grind until the slurry particle size D50 is 200-400 nm. Spray dry to obtain the first spray material.
[0010] S2. Add iron source, phosphorus source, lithium source, first carbon source, second carbon source, and dopant to deionized water and mix. Disperse by ultrasonication for 20-30 minutes, then transfer to a sand mill and grind until the slurry particle size D50 is 1-3 μm. Spray dry to obtain the second spray material.
[0011] S3. Mix the first spray material with the second spray material to obtain a mixed spray material. Place the mixed spray material into a tube furnace for sintering and then crush it to obtain high-pressure lithium iron phosphate.
[0012] The preparation mechanism of high-pressure lithium iron phosphate is as follows:
[0013] In a sand mill, high-speed rotating grinding media further break down particles in the slurry through impact, shearing, and friction. When the slurry is spray-dried, it is dispersed into fine droplets by an atomizer. Upon contact with hot air, the moisture evaporates rapidly, and the solutes in the raw materials precipitate out in solid form and agglomerate into spherical particles. The first and second spray-dried materials form nano-sized and micron-sized spherical particles, respectively. During the sintering process in a tubular furnace, high temperature causes the lithium source, iron source, and phosphorus source to undergo a solid-phase reaction to generate lithium iron phosphate crystals. The first and second carbon sources pyrolyze at high temperature to generate amorphous carbon, which uniformly coats the surface of the lithium iron phosphate particles. After lithium iron phosphate particles of different sizes are mixed and sintered with carbon sources, nanoparticles fill the gaps between micron-sized particles, and the carbon layer acts as a bridge to connect adjacent particles, forming a three-dimensional conductive network, resulting in high-pressure lithium iron phosphate.
[0014] Furthermore, the iron source includes at least one of anhydrous ferric phosphate, ferrous oxalate, iron(II,III) oxide, or ferric oxide; the phosphorus source includes at least one of ferric phosphate, ammonium dihydrogen phosphate, lithium dihydrogen phosphate, or lithium monohydrogen phosphate; the lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium acetate, or lithium hydroxide; and the molar ratio of iron atoms, phosphorus atoms, and lithium atoms is 0.96-0.98:1:1.00-1.08.
[0015] Furthermore, the first carbon source is at least one of glucose, hydroxypropyl β-cyclodextrin, sucrose, or citric acid, and the amount added is 3-10% of the iron source mass ratio; the second carbon source is at least one of polyethylene glycol, modified polyethylene glycol, or highly conductive polyaniline, and the amount added is 2-6% of the iron source mass.
[0016] Furthermore, the dopant is at least one of titanium dioxide, boron trioxide, and phosphoric acid, and the amount added is 1-2% of the mass of the iron source.
[0017] Furthermore, in step S1, in mixture two, the amount of the first carbon source added is 7-10% by weight, the amount of the second carbon source added is 4-6%, and the amount of titanium dioxide added is 0.4-1%.
[0018] Furthermore, in step S2, in mixture two, the amount of the first carbon source added is 3-6% by weight, the amount of the second carbon source added is 2-4%, the amount of titanium dioxide added is 0-0.4%, the amount of boron trioxide added is 0-0.4%, and the amount of phosphoric acid added is 0-2%.
[0019] Furthermore, in step S3, the weight ratio of the first spray material to the second spray material is 5-9:1-4; the sintering temperature is 750-810℃, and the sintering time is 6-10h.
[0020] This invention also proposes an application of high-density lithium iron phosphate, in which the high-density lithium iron phosphate prepared by the above-mentioned high-density lithium iron phosphate preparation method is applied to lithium iron phosphate cathode materials.
[0021] The present invention has the following beneficial effects:
[0022] 1. This invention optimizes particle size distribution by controlling the grinding particle size, carbon content, element doping, and additive content of high-compact lithium iron phosphate through reverse analysis. Different sizes of lithium iron phosphate can be directly prepared using sprayed materials with varying carbon source additions. Therefore, sintering a mixture of two sprayed materials in a specific ratio ensures both the uniformity of the carbon source and the presence of particles of different sizes. Using phosphoric acid as an additive reduces the iron-to-phosphorus ratio, i.e., phosphorus is relatively excessive, which promotes crystallization and preferred orientation. This orientation facilitates the formation of a more regular crystal structure, reduces crystal defects and porosity, and thus increases compaction density.
[0023] 2. This invention utilizes nano-sized particles to fill the gaps between micron-sized particles through different grinding particle sizes, forming a structure similar to close packing. This significantly reduces porosity. The high surface energy of the nanoparticles promotes particle rearrangement and grain boundary diffusion during sintering, reducing internal voids and further improving material density, laying the foundation for increased battery energy density. The first carbon source pyrolysis generates a thin and uniform amorphous carbon coating layer, reducing the contact resistance between lithium iron phosphate particles. The second carbon source constructs a three-dimensional conductive network, forming a dual conductive channel of particle coating and network connection. The carbon layer encapsulates the nanoparticles, preventing agglomeration caused by excessive surface energy during sintering, maintaining the dispersion of nanoparticles, and ensuring unobstructed ion diffusion paths. Furthermore, the spray-dried material gradation preparation process is relatively simple and does not require complex post-processing steps. This process can reduce raw material waste and energy consumption, thereby reducing production costs. No toxic reagents are used in the synthesis process, and the carbon dioxide and water vapor generated during spray drying and sintering can be treated to meet emission standards, complying with green manufacturing requirements. Attached Figure Description
[0024] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0025] Figure 1 This is a scanning electron microscope image of Example 2;
[0026] Figure 2 This is a comparative scanning electron microscope image. Detailed Implementation
[0027] The technical solution of the present invention will be clearly and completely described below with reference to the embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.
[0028] In this application, the glucose was obtained from Shenyang Elepx Chemical Co., Ltd., with CAS number 58367-01-4 and a purity of 98.5%.
[0029] In this application, the polyethylene glycol is from Nantong Chenrun Chemical Co., Ltd., CAS number 25322-68-3, with a density of 1.27 g / cm³. 3 The model number is PEG-400.
[0030] Example 1
[0031] This embodiment provides a method for preparing high-pressure lithium iron phosphate, including the following steps:
[0032] S1. Preparation of the first spray material
[0033] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 140g of glucose, 50g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 300nm. Then transfer it to a spray dryer for spray drying to obtain the first spray material.
[0034] S2, Prepare the second spray material
[0035] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 140g of glucose, 50g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 800nm. Then transfer it to a spray dryer for spray drying to obtain the second spray material.
[0036] S3, Preparation of lithium iron phosphate
[0037] The first spray material and the second spray material were dry-mixed in a V-type mixer at a ratio of 4:6 for 4 hours to obtain a mixed spray material. The mixed spray material was sintered at 790℃ for 10 hours and then pulverized to obtain the finished lithium iron phosphate product.
[0038] Example 2
[0039] This embodiment provides a method for preparing high-pressure lithium iron phosphate, including the following steps:
[0040] S1. Preparation of the first spray material
[0041] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 160g of glucose, 62g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the first spray material.
[0042] S2, Prepare the second spray material
[0043] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 70g of glucose, 25g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the second spray material.
[0044] S3, Preparation of lithium iron phosphate
[0045] The first spray material and the second spray material were dry-mixed in a V-type mixer at a ratio of 3:7 for 4 hours to obtain a mixed spray material. The mixed spray material was sintered at 790℃ for 10 hours and then pulverized to obtain the finished lithium iron phosphate product.
[0046] Example 3
[0047] This embodiment provides a method for preparing high-pressure lithium iron phosphate, including the following steps:
[0048] S1. Preparation of the first spray material
[0049] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 120g of glucose, 70g of polyethylene glycol, and 7g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the first spray material.
[0050] S2, Prepare the second spray material
[0051] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 160g of glucose, 60g of polyethylene glycol, and 1g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the second spray material.
[0052] S3, Preparation of lithium iron phosphate
[0053] The first spray material and the second spray material were dry-mixed in a V-type mixer at a ratio of 5:5 for 4 hours to obtain a mixed spray material. The mixed spray material was sintered at 800℃ for 10 hours and then pulverized to obtain the finished lithium iron phosphate product.
[0054] Example 4
[0055] This embodiment provides a method for preparing high-pressure lithium iron phosphate, including the following steps:
[0056] S1. Preparation of the first spray material
[0057] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 130g of glucose, 55g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the first spray material.
[0058] S2, Prepare the second spray material
[0059] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 140g of glucose, 50g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the second spray material.
[0060] S3, Preparation of lithium iron phosphate
[0061] The first spray material and the second spray material were dry-mixed in a V-type mixer at a ratio of 6:4 for 4 hours to obtain a mixed spray material. The mixed spray material was sintered at 795℃ for 10 hours and then pulverized to obtain the finished lithium iron phosphate product.
[0062] Example 5
[0063] This embodiment provides a method for preparing high-pressure lithium iron phosphate, including the following steps:
[0064] S1. Preparation of the first spray material
[0065] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 140g of glucose, 50g of polyethylene glycol, and 4g of titanium dioxide, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the first spray material.
[0066] S2, Prepare the second spray material
[0067] Weigh out 2000g of anhydrous ferric phosphate, 500g of lithium carbonate, 140g of glucose, 50g of polyethylene glycol, and 34g of phosphoric acid, and disperse them in 8.8L of deionized water. Transfer the dispersion to a sand mill for fine grinding until the particle size D50 of the slurry is 350nm. Then transfer it to a spray dryer for spray drying to obtain the second spray material.
[0068] S3, Preparation of lithium iron phosphate
[0069] The first and second spray materials were dry-mixed in a V-type mixer at a ratio of 8:2 for 4 hours to obtain a mixed spray material. The mixed spray material was sintered at 785℃ for 10 hours, and then pulverized to obtain the finished lithium iron phosphate product.
[0070] Comparative Example 1
[0071] The difference between this comparative example and Example 5 is that step S2 is omitted, and the spray material obtained in step S1 is directly sintered and pulverized to obtain lithium iron phosphate.
[0072] Performance testing:
[0073] The powder compaction density of lithium iron phosphate cathode materials prepared in Examples 1 to 5 and comparative examples and the coin cells prepared from each cathode material were determined in accordance with the standard GB / T 44330-2024 "Determination of Powder Compacted Density of Cathode Materials for Lithium-ion Batteries".
[0074] The discharge specific capacity of the lithium iron phosphate cathode materials prepared in Examples 1-5 and the comparative examples, as well as the coin cells prepared from each cathode material, were determined according to standard GB / T 42161-2022 "Methods for Testing the Electrochemical Performance of Lithium Iron Phosphate: First Discharge Specific Capacity and First Charge-Discharge Efficiency". The specific test results are shown in Table 1 below:
[0075] Table 1 – Performance Test Data of Samples
[0076]
[0077]
[0078] Data Analysis:
[0079] Comparative analysis of the data in Table 1 above shows that the lithium iron phosphate cathode material prepared by this invention, by controlling at least one of the grinding particle size, carbon source addition amount, dopant, and additives in Examples 1-5 to achieve particle size gradation, has a compaction density superior to the comparative example. This indicates that by adjusting different grinding particle sizes, carbon content, element doping amounts, and additives to obtain different spray materials, and then performing particle gradation on them, spherical secondary particles with reasonable particle size gradation are formed, reducing interparticle voids, optimizing powder packing efficiency, and improving the compaction density of the material.
[0080] The preferred embodiments of the present invention disclosed above are merely illustrative of the invention. These preferred embodiments do not exhaustively describe all details, nor do they limit the invention to specific implementations. Clearly, many modifications and variations can be made based on the content of this specification. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to better understand and utilize the invention. The invention is limited only by the claims and their full scope and equivalents.
Claims
1. A method for preparing high-pressure lithium iron phosphate, characterized in that, Includes the following steps: S1. Add iron source, phosphorus source, lithium source, first carbon source, second carbon source, and dopant to deionized water and mix. Disperse ultrasonically for 20-30 minutes to obtain mixture one. Then transfer it to a sand mill and grind it finely until the slurry particle size is 200-400nm. Spray dry to obtain the first spray material. S2. Add iron source, phosphorus source, lithium source, first carbon source, second carbon source, and dopant to deionized water and mix. Disperse by ultrasonication for 20-30 minutes to obtain mixture two. Then transfer it to a sand mill and grind it into a slurry with a particle size of 1-3 μm. Spray dry to obtain second spray material. S3. Mix the first spray material with the second spray material to obtain a mixed spray material. Place the mixed spray material into a tube furnace for sintering and then crush it to obtain high-pressure lithium iron phosphate.
2. The method for preparing high-pressure lithium iron phosphate according to claim 1, characterized in that, The iron source includes at least one of anhydrous ferric phosphate, ferrous oxalate, iron(II,III) oxide, or ferric oxide; the phosphorus source includes at least one of ferric phosphate, ammonium dihydrogen phosphate, lithium dihydrogen phosphate, or lithium monohydrogen phosphate; the lithium source includes at least one of lithium carbonate, lithium dihydrogen phosphate, lithium acetate, or lithium hydroxide; and the molar ratio of iron atoms, phosphorus atoms, and lithium atoms is 0.96-0.98:1:1.00-1.
08.
3. The method for preparing high-pressure lithium iron phosphate according to claim 1, characterized in that, The first carbon source is at least one of glucose, hydroxypropyl β-cyclodextrin, sucrose or citric acid, and the amount added is 3-10% of the iron source mass ratio; the second carbon source is at least one of polyethylene glycol or highly conductive polyaniline, and the amount added is 2-6% of the iron source mass.
4. The method for preparing high-pressure lithium iron phosphate according to claim 1, characterized in that, The dopant is at least one of titanium dioxide, boron trioxide, and phosphoric acid, and the amount added is 1-2% of the mass of the iron source.
5. The method for preparing high-pressure lithium iron phosphate according to claim 1, characterized in that, In step S1, in mixture two, the amount of the first carbon source added is 7-10% by weight, the amount of the second carbon source added is 4-6%, and the amount of titanium dioxide added is 0.4-1%.
6. The method for preparing high-pressure lithium iron phosphate according to claim 1, characterized in that, In step S2, in mixture two, the amount of the first carbon source added is 3-6% by weight, the amount of the second carbon source added is 2-4%, the amount of titanium dioxide added is 0-0.4%, the amount of boron trioxide added is 0-0.4%, and the amount of phosphoric acid added is 0-2%.
7. The method for preparing high-pressure lithium iron phosphate according to claim 1, characterized in that, In step S3, the weight ratio of the first spray material to the second spray material is 5-9:1-4; the sintering temperature is 750-810℃, and the sintering time is 6-10h.
8. An application of high-pressure lithium iron phosphate, characterized in that, The high-density lithium iron phosphate prepared by the high-density lithium iron phosphate preparation method according to any one of claims 1-7 is applied to lithium iron phosphate cathode materials.