CN-121983548-A - Lithium iron manganese phosphate composite material, preparation method thereof and secondary battery containing lithium iron manganese phosphate composite material

CN121983548ACN 121983548 ACN121983548 ACN 121983548ACN-121983548-A

Abstract

The invention belongs to the field of batteries, and particularly discloses a lithium iron manganese phosphate composite material, a preparation method thereof and a secondary battery containing the same. The preparation method comprises the steps of firstly preparing manganese iron phosphate containing a special pore-forming agent, then mixing the manganese iron phosphate serving as a precursor with raw materials such as a lithium source, a doped metal element M source, a carbon source and the like, respectively grinding the mixture into large and small particle mixtures with different particle diameters, grinding and mixing the large and small particle mixtures, spray-drying the large and small particle mixtures to obtain an unsintered precursor mixture, and finally sintering the unsintered precursor mixture through twice heat treatment to obtain the manganese iron lithium phosphate composite material. The method can lead the lithium iron manganese phosphate composite material to have the advantages of high compaction density, high rate capability, low cost and high gram capacity play, and widens the application prospect of the material.

Inventors

WANG YUNJIE
ZHENG YOUSHUI
LEI CHAO
ZHANG CHEN
ZHENG HUANRAN
LU ZHICAI

Assignees

金龙羽新能源(深圳)有限公司

Dates

Publication Date: 20260505
Application Date: 20260204

Claims (10)

1. The preparation method of the lithium iron manganese phosphate composite material is characterized by comprising the following steps of: (1) Dissolving the first pore-forming agent in a solvent, adding the second pore-forming agent and the solid electrolyte, and sequentially performing ball milling, spray drying, heat treatment and crushing to obtain a third pore-forming agent; the decomposition temperature of the first pore-forming agent is T1, and the decomposition temperature of the second pore-forming agent is T2; (2) Under the protection of inert gas, dropwise adding an alkaline solution into the first mixture for precipitation reaction, adding a third pore-forming agent, washing, filtering and drying to obtain a second mixture, wherein the pH value of the precipitation reaction is 5.5-8; (3) Mixing the second mixture, a lithium source, a metal element M doped source, a carbon source and a solvent to obtain a third mixture; Taking one part of the third mixture and grinding the third mixture to slurry 1 with an average particle size d 1; Taking another part of the third mixture, and grinding the third mixture to obtain slurry 2 with an average particle size of d2, wherein d1 and d2 satisfy the following relationship that d1< d2; (4) Sequentially ball-milling and spray-drying the slurry 1 and the slurry 2 to obtain a fourth mixture, wherein the average particle size of the fourth mixture is less than or equal to 10 mu m; (5) Sequentially performing primary sintering, secondary sintering and cooling on the fourth mixture to obtain the lithium iron manganese phosphate composite material; the sintering temperature of the first sintering is T3, the sintering temperature of the second sintering is T4, and T1< T3< T2< T4 are satisfied.
2. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, comprising at least one of the following a-B: A. In the step (1), the first pore-forming agent comprises at least one of nylon, ammonium carbonate, ammonium bicarbonate, ammonium oxalate, polymethacrylate, methyl methacrylate, methylcellulose, polyvinyl alcohol, carboxymethyl cellulose, ascorbic acid, polyfurfuryl alcohol or polymethyl methacrylate; B. In the step (1), the second pore-forming agent comprises at least one of polystyrene, polyvinyl butyral, modified graphene or modified wood particles, and the modified graphite comprises graphene oxide.
3. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, wherein in the step (2), the mass percentage of the third pore-forming agent is 1-30% based on the total mass of the ferrous source, the manganese source and the phosphorus source in the solution containing the ferrous source and the manganese source and the solution containing the phosphorus source.
4. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, comprising at least one of the following C-D: C. in the step (5), the temperature of the T3 is 250-400 ℃, the temperature rising speed of the T3 is 0.5-15 ℃ per minute, and the time of the first sintering is 0.5-6h; D. In the step (5), the temperature of the T4 is 580-700 ℃, the temperature rising speed of the T4 is 0.5-15 ℃ per minute, and the time of the second sintering is 4-26 hours.
5. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, comprising at least one of the following E to K: E. in the step (1), the solid electrolyte comprises at least one of lithium aluminum titanium phosphate, lithium germanium aluminum phosphate, lithium lanthanum titanate or lithium lanthanum zirconium oxide; F. In step (1), the solvent comprises at least one of ethanol or water; G. in the step (1), the mass ratio of the first pore-forming agent to the second pore-forming agent to the solid electrolyte is (1-9): 1-9; H. In the step (1), the ball milling time is 1-3 hours; I. In the step (1), the air inlet temperature of the spray drying is 150-220 ℃, and the air outlet temperature of the spray drying is 65-110 ℃; J. in the step (1), the temperature of the heat treatment is 95-110 ℃, and the time of the heat treatment is 0.5-3h; K. in the step (1), the average particle size of the third pore-forming agent is 10-100nm.
6. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, comprising at least one of the following L-V: l, in the step (2), in the solution containing the ferrous source and the manganese source, the ferrous source comprises at least one of ferrous chloride, ferrous sulfate or ferrous nitrate; M, in the step (2), in the solution containing the ferrous source and the manganese source, the manganese source comprises at least one of manganese chloride, manganese sulfate or manganese nitrate; In the step (2), the mass percentage of Fe and Mn in the solution containing the ferrous source and the manganese source is 3-20% and 3-20% respectively; O, in the step (2), the phosphorus source comprises at least one of ammonium phosphate, monoammonium phosphate, diammonium phosphate or phosphoric acid in the solution containing the phosphorus source; p, in the step (2), the pH value of the solution containing the phosphorus source is 6-8, and the mass percentage of P in the solution containing the phosphorus source is 3% -20%; Q, in the step (2), the molar ratio of Fe in the ferrous source to Mn in the manganese source to P in the phosphorus source in the solution containing the ferrous source to the solution containing the manganese source is (1-9): 10-13; R, in the step (2), the alkali in the alkaline solution comprises at least one of ammonia water, sodium hydroxide or sodium carbonate; s, in the step (2), the time of the precipitation reaction is 0.5-8h; in the step (2), the dripping time is less than 6 hours; u, in the step (2), the drying temperature is 100-220 ℃; v, in the step (2), the average particle size of the second mixture is less than 200 mu m.
7. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, comprising at least one of the following I to X: I. in the step (3), the lithium source comprises at least one of lithium hydroxide, lithium carbonate, lithium dihydrogen phosphate, lithium oxalate, lithium acetate or lithium phosphate; II. In the step (3), the metal element M in the doped metal element M source comprises at least one of Ti, mg, al, V, nb or Zn, and the doped metal element M source comprises at least one of oxide or salt of the metal element M; III, in the step (3), the carbon source comprises at least one of starch, sucrose, glucose, citric acid, polyethylene glycol, polyvinylpyrrolidone, polypropylene, conductive carbon black, acetylene black, carbon nanotubes or graphene; IV, step (3), wherein the solvent comprises water; V, in the step (3), the third mixture further comprises a solid electrolyte, wherein the solid electrolyte comprises at least one of lithium aluminum titanium phosphate, lithium aluminum germanium phosphate, lithium lanthanum titanate or lithium lanthanum zirconium oxide; VI, in the step (3), the second mixture contains Fe element, mn element and P element, and the molar ratio of the Li element in the lithium source, the Fe element in the second mixture and the metal element M in the doped metal element M source is (1-1.06): (0.25-0.45): (0.001-0.03); VII, in the step (3), the mass percentage of the carbon source is 1% -8% based on the total mass of the second mixture, the lithium source and the doped metal element M source; VIII, in the step (3), the mass percent of the solid electrolyte is 0-10% based on the total mass of the second mixture, the lithium source and the doped metal element M source; IX, in step (3), the mass percent of solvent in the third mixture is 40% -80% based on the mass of the third mixture; In the step (3), the solid content of the third mixture is 10-90 wt%, d1 is 0.1-0.4 μm, and d2 is 0.3-1 μm.
8. The method of preparing a lithium iron manganese phosphate composite material according to claim 1, comprising at least one of the following a to d: a. In the step (4), the mass ratio of the slurry 1 to the slurry 2 is (2-9): 1-8; b. in the step (4), the air inlet temperature of the spray drying is 150-220 ℃, and the air outlet temperature of the spray drying is 65-110 ℃; c. in the step (4), the average particle size of the fourth mixture is 2-9 μm; d. In the step (4), the ball milling time is 10-30min.
9. A lithium iron manganese phosphate composite material prepared by the method for preparing a lithium iron manganese phosphate composite material according to any one of claims 1 to 8.
10. A secondary battery comprising a positive electrode sheet, a negative electrode sheet, and an electrolyte, wherein the positive electrode sheet comprises the lithium iron manganese phosphate composite material according to claim 9.

Description

Lithium iron manganese phosphate composite material, preparation method thereof and secondary battery containing lithium iron manganese phosphate composite material Technical Field The invention belongs to the field of batteries, and particularly relates to a lithium iron manganese phosphate composite material, a preparation method thereof and a secondary battery containing the same. Background Lithium iron manganese phosphate (LMFP) has excellent thermodynamic, kinetic stability and safety properties, and is widely used in commercial batteries. The LMFP is mainly realized by two modes of a liquid phase method and a solid phase method. The liquid phase method can be further classified into a hydrothermal method, a solvothermal method, a sol-gel method, a coprecipitation method, and the like. The hydrothermal method has the advantages of the most wide application range, low energy consumption and low cost, and can control the particle size of the product, but because the hydrothermal method is produced under the environment of high temperature and high pressure, the hydrothermal method has high requirements on equipment and operation control, cannot be popularized on a large scale, and has poor consistency of different batches of the product and high industrialization difficulty. The solid phase method for preparing LMFP has the problems of uneven reaction, large particle size, difficult morphology control and poor batch consistency. The LMFP prepared by the liquid phase method has good consistency, but has higher cost, and still has the problems of low compaction density, low electronic conductivity, low lithium ion diffusion rate, poor multiplying power performance and lower gram capacity exertion, and cannot effectively improve the compaction density and gram capacity exertion of the LMFP, so that the application scene of the LMFP is limited. The ferric manganese phosphate (MFP) has good chemical stability, is not easy to deteriorate in the storage and transportation processes, can be selected by a plurality of synthetic methods, and can select a proper process route according to actual conditions. Meanwhile, the MFP is used as a precursor of the LMFP by a liquid phase method, the purity requirement on the MFP is high, if the MFP contains impurities, the performance of the LMFP is influenced, and Me/P and Mn/Fe of the MFP greatly influence the performance of the LMFP. In addition, the granularity and the microscopic morphology of the MFP have larger influence on the performance of the LMFP, and the microscopic morphology of the conventional MFP has more sheets. When the MFP is used as a precursor to prepare the lithium iron manganese phosphate, the MFP and other raw materials are generally required to be mixed by grinding or sanding, but the flaky MFP is not easy to grind and disperse into primary particles, which is not beneficial to forming proper gradation in the subsequent stage, so that the electrical property of the LMFP is difficult to improve by controlling the MFP particles. In addition, in general, pore-forming agents are added in the process of preparing the MFP by precipitation, and then the precipitated product is sintered, and the pore-forming agents are decomposed at high temperature to generate gas so as to improve the porosity of the MFP and improve the particle performance of the MFP. However, high temperature sintering is required during the pore-forming of the MFP further obviously improving the production cost. Disclosure of Invention Aiming at the problems of low compaction density, gram capacity, rate capability and the like of the LMFP prepared by taking the MFP as a precursor in the prior art, the invention provides a lithium iron manganese phosphate composite material, a preparation method thereof and a secondary battery containing the lithium iron manganese phosphate composite material. In order to achieve the above purpose, the method specifically comprises the following technical scheme: In a first aspect, a method for preparing a lithium iron manganese phosphate composite material includes the steps of: (1) Dissolving a first pore-forming agent in a solvent, adding a second pore-forming agent and a solid electrolyte, and sequentially performing ball milling, spray drying, heat treatment and crushing to obtain a third pore-forming agent, wherein the decomposition temperature of the first pore-forming agent is T1, and the decomposition temperature of the second pore-forming agent is T2; (2) Under the protection of inert gas, dropwise adding an alkaline solution into the first mixture for precipitation reaction, adding a third pore-forming agent, washing, filtering and drying to obtain a second mixture, wherein the pH value of the precipitation reaction is 5.5-8; (3) Mixing the second mixture, a lithium source, a metal element M doped source, a carbon source and a solvent to obtain a third mixture; Taking one part of the third mixture and grinding the third mixture to slurry 1 w