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Method for synthesizing high-density lithium iron phosphate material

A technology of lithium iron phosphate and synthesis method, applied in phosphorus compounds, chemical instruments and methods, inorganic chemistry and other directions, can solve the problems of agglomerate accumulation of conductive agents, residual ferric iron, affecting the performance of lithium iron phosphate materials, etc. The effect of increasing volume specific energy and increasing bulk density

Inactive Publication Date: 2011-10-05
天津恒普科技发展有限公司
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

This method results in agglomerated buildup of the conductive agent
Patent CN100486004C proposes a method for preparing lithium iron phosphate by reacting ferric salt and lithium dihydrogen phosphate, but since there is no reducing agent in this method, a large amount of ferric iron will be left, which will affect the performance of lithium iron phosphate material
Since iron ions are produced by the decomposition of iron salts, there are problems such as that the particles of the product will not achieve densification

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0024] The synthesis method of high-density lithium iron phosphate material, first dry and dehydrate iron phosphate at 200°C for 10 hours, and then dry ball mill 50g of dehydrated iron phosphate and 5.6g lithium powder in dry air with a relative humidity of 1%. , for mixing. At this time, the molar ratio of iron phosphate to lithium powder is 1:0.8. On the surface of the mixed material, apply a pressure of 0.1MPa with a ceramic mold, and heat at 400°C for 1 hour without air to generate pure phase lithium iron phosphate. The obtained lithium iron phosphate was pulverized and immersed in 55.6 g of polyvinyl butyral ethanol solution. Wherein, the weight percent of polyvinyl butyral in the solution is 1%. Then the system is dried at 100°C, and then calcined at 500°C for 10 hours to form a lithium iron phosphate material with a thin carbon film on the surface. The tap density of the material can reach 1.72g / cm 3 .

Embodiment 2

[0026] The synthesis method of high-density lithium iron phosphate material, first, dry and dehydrate iron phosphate at 700°C for 1 hour, and then dehydrate 50Kg of iron phosphate and 8.4Kg of lithium powder in a dry air environment with a relative humidity of 1%. Jet milling for mixing. At this time, the molar ratio of iron phosphate to lithium powder is 1:1.2. On the surface of the mixed material, apply a pressure of 10MPa with a ceramic mold, and then heat at 300°C for 5 hours without air to generate pure phase lithium iron phosphate. After the obtained lithium iron phosphate was pulverized, it was immersed in a 584Kg polyvinyl butyral ethanol solution. The weight percent concentration of polyvinyl butyral in the solution is 20%. Then the system is dried at 120°C, and then calcined at 600°C for 1 hour to form a lithium iron phosphate material with a thin carbon film on the surface. The tap density of the material can reach 1.80g / cm 3 .

Embodiment 3

[0028] The synthesis method of high-density lithium iron phosphate material, first, dry and dehydrate iron phosphate at 400°C for 4 hours, and then dry the dehydrated iron phosphate 100Kg and 70Kg lithium powder in a dry air environment with a relative humidity of 1.5%. Ball mill mixture. At this time, the molar ratio of iron phosphate to lithium powder is 1:1. On the surface of the mixed material, apply a pressure of 5MPa with a ceramic mold, and then heat at 350°C for 3 hours without air to generate pure phase lithium iron phosphate. After crushing the obtained lithium iron phosphate, immerse in 850Kg polyvinyl butyral ethanol solution. The weight percentage concentration of polyvinyl butyral in this solution is 5%. Then the system is dried at 110°C, and then calcined at 550°C for 5 hours to form a lithium iron phosphate material with a thin carbon film on the surface. The tap density of the material can reach 1.75g / cm 3 .

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Abstract

The invention relates to a method for synthesizing a high-density lithium iron phosphate material, belonging to the technical field of cathode materials of lithium ion batteries. The method for synthesizing the high-density lithium iron phosphate material comprises the following technical steps of: 1, synthesizing pure-phase lithium iron phosphate: firstly, drying and dehydrating iron phosphate for 1-10 hours at the temperature of 200-700 DEG C, and uniformly mixing the dehydrated iron phosphate with metal lithium powder in the atmosphere of dry air or inert gas; and applying the pressure of 0.1-10MPa to the surface of an iron phosphate and lithium powder mixed material, and heating for 1-5 hours at the temperature of 300-400 DEG C in an air isolation way; 2, cladding a thin carbon layer: crushing lithium iron phosphate, and then immersing into a polyvinyl butyral / ethanol solution, wherein the concentration of the polyvinyl butyral is 1-20%, and the weight ratio of the lithium iron phosphate to the solution is 1:(1-10); and 3, baking and calcining: baking at the temperature of 100-120 DEG C, and calcining for 1-10 hours at the temperature of 500-600 DEG C. The method provided by the invention has the advantages of simple process and convenience for operation, and the high-density lithium iron phosphate material has the advantages of stable quality, high material packing density, low carbon content, high gram capacity, high energy density per unit volume and the like.

Description

technical field [0001] The invention belongs to the technical field of lithium ion battery cathode materials, and in particular relates to a synthesis method of a high-density lithium iron phosphate material. Background technique [0002] At present, the application fields of lithium-ion batteries are becoming wider and wider. Lithium iron phosphate power batteries in particular have safety, cycle life and high-temperature performance unmatched by other cathode materials, and are widely used in electric vehicles and other fields. However, the performance of lithium iron phosphate materials is generally poor, especially in indicators such as discharge capacity and density. The existing technology generally adopts ferrous oxalate or ferric phosphate system, which is made by adding additives such as lithium source and carbon source, and sintering at high temperature. The sintering temperature is generally not lower than 650°C. Under high temperature conditions, the carbon so...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01B25/45H01M4/1397
CPCY02E60/122Y02E60/12Y02E60/10
Inventor 胡学仁
Owner 天津恒普科技发展有限公司
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