Preparation method of lithium iron phosphate material with low carbon content and high rate capability
The preparation of low-carbon micron lithium iron phosphate material through heterogeneous spray drying method is solved, and the problems of poor electronic conductivity and lithium ion diffusion kinetics of lithium iron phosphate materials are achieved, and the performance improvement of high magnification and high energy density is achieved, and at low temperatures are achieved. Maintain good discharge capacity.
Patent Information
- Application Number
- CN202411244505.2
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-06
- Publication Date
- 2024-12-13
AI Technical Summary
In the electric vehicles and energy storage fields, the existing lithium iron phosphate materials are difficult to meet the needs of high magnification and high energy density due to low electronic conductivity and poor lithium ion diffusion kinetics, and the carbon coating is difficult to achieve uniform coating, resulting in performance. decline.
The low-carbon micron-sized lithium iron phosphate material is prepared by heterogeneous spray drying. By coating it at one time, a uniform carbon coating is formed, which improves the electronic conductivity and lithium ion diffusion kinetics of the material, and improves the rate performance and energy density.
It has achieved the improvement of the conductivity and anti-aging ability of lithium iron phosphate materials under low carbon content, meet the needs of high energy density and high rate performance, and maintain a high discharge capacity at low temperatures.
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Figure CN119133394A_ABST
Abstract
Description
Technical Field
[0001] The present invention relates to the technical field of preparation methods of lithium iron phosphate materials, and in particular to a preparation method of lithium iron phosphate materials with low carbon content and high rate performance. Background Art
[0002] As we all know, lithium-ion batteries, as a clean and renewable energy source, are widely used in electric vehicles, power storage and other fields. The positive electrode material determines the performance and cost of the battery. Compared with layered ternary positive electrode materials, LiFePO4 (LFP) positive electrode materials are widely accepted and used due to their low cost, high safety and good cycle performance.
[0003] The application of LFP faces bottlenecks in the fields of electric vehicles and energy storage. In the field of electric vehicles, LFP is difficult to apply to high-power vehicles due to its low electronic conductivity and poor lithium ion diffusion kinetics. In addition, due to limited vehicle space, LFP has a low volume energy density and it is difficult to achieve maximum cruising range. In the field of energy storage, LFP's low volume energy density makes it difficult to face the challenge of increasing the capacity of a single battery. The increase in the capacity of a single battery will inevitably reduce the cost per watt-hour, which requires LFP to have a higher volume energy density. Thickening the electrode and placing more LFP in the same casing can help increase the capacity of a single battery. However, thickening the electrode will greatly reduce the rate performance of a single battery, resulting in the nominal power of almost all large-capacity batteries on the market being only 0.25C.
[0004] The prior art has proposed various methods to improve rate performance, among which carbon coating and nano-sizing are the most commonly used methods to improve LFP rate performance. Surface carbon coating can effectively enhance the overall electronic conductivity of particles and electrodes, while nano-sizing can effectively shorten the ion transfer path and improve diffusion kinetics. However, experiments have confirmed that micron-sized particles will form a dense stack when stacked, and particles that are too large will lead to a decrease in the performance of the prepared battery. It is also difficult to achieve uniform mixing and coating of the surface carbon coating. Therefore, it is very difficult to form a uniform coating with a low carbon content on lithium iron phosphate materials. Summary of the invention
[0005] 1. Technical issues to be resolved
[0006] In view of the shortcomings of the prior art, the present invention provides a method for preparing a lithium iron phosphate material with a low carbon content and high rate performance, which prepares a low-carbon micron-sized lithium iron phosphate material by a heterogeneous spray drying method. The corresponding preparation method has a simple process and low cost. The lithium iron phosphate material obtained by one coating has a more uniform coating layer while ensuring a low carbon content, and the electrical conductivity of the material is improved, which can meet the requirements of high energy density and high rate performance. In addition, the electrochemical performance does not decay significantly after contact with air, and the anti-aging ability is significantly improved.
[0007] (II) Technical solution
[0008] To achieve the above object, the present invention provides the following technical solution: a method for preparing a lithium iron phosphate material with low carbon content and high rate performance, comprising the following steps:
[0009] S1: adding the iron source and lithium source of the raw materials for preparing lithium iron phosphate into deionized water in a certain proportion, and continuously stirring at room temperature to obtain a primary mixed system;
[0010] S2. Adding a second iron source, a phosphorus source and a carbon source to the primary mixed system obtained in the previous step to prepare a secondary mixed system;
[0011] S3: granulating the secondary mixed system obtained in the previous step by using a spray dryer to obtain a precursor powder;
[0012] S4: sintering the dried precursor powder obtained in the previous step under an inert atmosphere, and cooling after sintering;
[0013] S5 crushes the sintered material cooled in the previous step to obtain a lithium iron phosphate material with a low carbon content.
[0014] Preferably, the iron source is ferric phosphate and ferrous sulfate, the lithium source is lithium hydroxide, the phosphorus source is one of diammonium phosphate and lithium dihydrogen phosphate, and the second carbon source is one of glucose and sucrose.
[0015] Furthermore, the molar ratio of the ferric phosphate to the ferrous sulfate is 1:1.
[0016] Furthermore, the molar ratio of the iron source and the lithium source in the primary mixed system is 1:1.02-1:1.04, the molar ratio of the phosphorus source, the lithium source and the iron source added further is 1:1.02:1-1:1.04:1, and the mass of the carbon source is 2.6±0.3wt% of iron phosphate.
[0017] As a further embodiment of the present invention, the inert gas is argon or nitrogen, the inlet temperature is 250-280°C, and the feed rate is 700-850 mL / h.
[0018] As a further embodiment of the present invention, the precursor powder is heated at a rate of 3-5°C / min in an inert atmosphere, and is first sintered at 350-400°C for 5 hours, and then sintered at 700-750°C for 10 hours.
[0019] As a further solution of this scheme, the median particle size d50 of the pulverized particles of the sintered material is controlled to be 0.8 to 2.5 μm.
[0020] The lithium iron phosphate prepared by the method for preparing a low-carbon content and high-rate performance lithium iron phosphate material is a low-carbon micron-sized lithium iron phosphate material prepared by a heterogeneous spray drying method, and the lithium iron phosphate material can maintain 135 mAh g at 10C. -1 gram capacity and maintains a high discharge capacity at low temperatures.
[0021] (III) Beneficial effects
[0022] Compared with the prior art, the present invention provides a method for preparing a lithium iron phosphate material with low carbon content and high rate performance, which has the following beneficial effects:
[0023] In the present invention, two iron sources and low carbon content are used to synthesize a low-carbon lithium iron phosphate material by a heterogeneous spray drying method. The material is stacked with uniformly coated carbon coating particles. Due to the close stacking of particles and uniform coating, the material has a higher energy density and excellent lithium ion diffusion kinetics, which ultimately improves the discharge capacity, rate performance and low-temperature discharge capability of the lithium iron phosphate material. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 It is a schematic diagram of the overall process framework of the present invention;
[0025] Figure 2 This is a SEM image of LFP of a specific embodiment of the present invention;
[0026] Figure 3 This is a SEM image of the positive electrode sheet prepared in the first specific embodiment of the present invention;
[0027] Figure 4 This is a graph of 8C discharge performance tested in specific embodiments 1 and 2 of the present invention;
[0028] Figure 5 This is a performance diagram of the discharge rate of -20°C to 25°C tested in the first and second embodiments of the present invention. DETAILED DESCRIPTION
[0029] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.
[0030] Example
[0031] See also Figure 1-Figure 5 , a method for preparing a lithium iron phosphate material with low carbon content and high rate performance, comprising the following steps:
[0032] S1: adding the iron source and lithium source of the raw materials for preparing lithium iron phosphate into deionized water in a certain proportion, and continuously stirring at room temperature to obtain a primary mixed system;
[0033] S2. Adding a second iron source, a phosphorus source and a carbon source to the primary mixed system obtained in the previous step to prepare a secondary mixed system;
[0034] S3: granulating the secondary mixed system obtained in the previous step by using a spray dryer to obtain a precursor powder;
[0035] S4: sintering the dried precursor powder obtained in the previous step under an inert atmosphere, and cooling after sintering;
[0036] S5 crushes the sintered material cooled in the previous step to obtain a lithium iron phosphate material with a low carbon content.
[0037] The iron source is ferric phosphate and ferrous sulfate, the molar ratio of the ferric phosphate to the ferrous sulfate is 1:1, the lithium source is lithium hydroxide, the phosphorus source is one of ammonium dihydrogen phosphate and lithium dihydrogen phosphate, the second carbon source is one of glucose and sucrose, the molar ratio of the iron source to the lithium source in the primary mixed system is 1:1.02-1:1.04, the molar ratio of the phosphorus source, lithium source and iron source added continuously is 1:1.02:1-1:1.04:1, the mass of the carbon source is phosphoric acid The inert gas is argon or nitrogen, the inlet temperature is 250-280°C, the feed rate is 700-850mL / h, the precursor powder is heated at a rate of 3-5°C / min in an inert atmosphere, and is first sintered at 350-400°C for 5h, and then sintered at 700-750°C for 10h, and the median particle size d50 of the sintered material after crushing is controlled to be 0.8-2.5μm.
[0038] The lithium iron phosphate prepared by the method for preparing a low-carbon content and high-rate performance lithium iron phosphate material is a low-carbon micron-sized lithium iron phosphate material prepared by a heterogeneous spray drying method, and the lithium iron phosphate material can maintain 135 mAh g at 10C. -1 gram capacity and maintains a high discharge capacity at low temperatures. Specific embodiment 1
[0040] Weigh 302g of ferric phosphate and 85.7g of LiOH·H2O, dissolve in deionized water, and stir continuously at room temperature to mix well. Continue to add 230g of NH4H2PO4, 85.7g of LiOH·H2O, 556g of FeSO4·7H2O and 32.3g of glucose and stir continuously to control the solid content to 35%. After sand milling, spray drying is performed to obtain a precursor powder. The precursor powder is sintered at an inlet temperature of 260°C and a feed rate of 800mL / h. The mixture is heated at 3°C min under an inert atmosphere. -1 The sample was heated at a speed of 300 °C and sintered at 350 °C for 5 h and 700 °C for 10 h to obtain micron-sized A-LFP material.
[0041] A-LFP material, Super-P, CNTs solution and PVDF binder are dispersed in NMP solvent, wherein the mass ratio of A-LFP:Super-P:CNTs:PVDF is 94:2.5:0.5:3. The paste is fully stirred and coated on aluminum foil. The electrode plate is dried in a vacuum oven at 100°C for 12 hours to remove the NMP solvent. Specific embodiment 2
[0043] Weigh 604g of ferric phosphate and 85.7g of LiOH·H2O, dissolve them in deionized water, stir continuously at room temperature, mix evenly, continue to add 230g of NH4H2PO4, 85.7g of LiOH·H2O and 32.3g of glucose and stir continuously, control the solid content to 35%, grind the mixture and spray dry it to obtain a precursor powder, sinter the precursor powder, the inlet temperature is 260℃, the feed rate is 800mL / h, and the temperature is 3℃ min under an inert atmosphere. -1 The samples were heated at a rate of , sintered at 350 °C for 5 h, and sintered at 700 °C for 10 h to obtain micron-sized B-LFP materials.
[0044] B-LFP material, Super-P, CNTs solution and PVDF binder are dispersed in NMP solvent, where the mass ratio of A-LFP:Super-P:CNTs:PVDF is 94:2.5:0.5:3. The paste is fully stirred and coated on aluminum foil. The electrode plate is dried in a vacuum oven at 100°C for 12 hours to remove the NMP solvent.
[0045] In summary, after the preparation of the two component materials of the specific embodiment 1 and the specific embodiment 2 and the attached specification Figure 2 , 3 The analysis and comparison of , 4 and 5 confirm that the low-carbon lithium iron phosphate material synthesized by the preparation method of the non-low-carbon-content high-rate performance lithium iron phosphate material has dense and uniform carbon coating particles, and the corresponding lithium iron phosphate material has a high energy density and excellent lithium ion diffusion kinetics, and improves the discharge capacity, rate performance and low-temperature discharge capability of the lithium iron phosphate material.
[0046] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.
Claims
1. A method for preparing a lithium iron phosphate material with low carbon content and high rate performance, characterized in that: The steps include: S1: adding the iron source and lithium source of the raw materials for preparing lithium iron phosphate into deionized water in a certain proportion, and continuously stirring at room temperature to obtain a primary mixed system; S2. Adding a second iron source, a phosphorus source and a carbon source to the primary mixed system obtained in the previous step to prepare a secondary mixed system; S3: granulating the secondary mixed system obtained in the previous step by using a spray dryer to obtain a precursor powder; S4: sintering the dried precursor powder obtained in the previous step under an inert atmosphere, and cooling after sintering; S5 crushes the sintered material cooled in the previous step to obtain a lithium iron phosphate material with a low carbon content.
2. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 1, characterized in that: The iron source is ferric phosphate and ferrous sulfate, the lithium source is lithium hydroxide, the phosphorus source is one of ammonium dihydrogen phosphate and lithium dihydrogen phosphate, and the second carbon source is one of glucose and sucrose.
3. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 2, characterized in that: The molar ratio of the ferric phosphate to the ferrous sulfate is 1:
1.
4. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 3, characterized in that: The molar ratio of the iron source and the lithium source in the primary mixed system is 1:1.02-1:1.04, and the molar ratio of the phosphorus source, the lithium source and the iron source added further is 1:1.02:1-1:1.04:
1. The mass of the carbon source is 2.6±0.3wt% of the iron phosphate.
5. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 4, characterized in that: The inlet temperature of the inert gas is 250-280° C., and the feed rate of the inert gas is 700-850 mL / h.
6. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 5, characterized in that: The precursor powder is heated at a rate of 3-5°C / min in an inert atmosphere, and is first sintered at 350-400°C for 5 hours, and then sintered at 700-750°C for 10 hours.
7. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 6, characterized in that: The median particle size d50 of the pulverized sintered material is controlled to be 0.8-2.5 μm.
8. The method for preparing a lithium iron phosphate material with low carbon content and high rate performance according to claim 8, characterized in that: The lithium iron phosphate prepared by the method for preparing a low-carbon content and high-rate performance lithium iron phosphate material is a low-carbon micron-sized lithium iron phosphate material prepared by a heterogeneous spray drying method, and the lithium iron phosphate material can maintain 135 mAh g at 10C. -1 gram capacity and maintains a high discharge capacity at low temperatures.