Method for preparing nanocrystalline lithium iron phosphate powder by adopting iron hydroxide colloid

Abstract

The invention relates to a method for preparing nanocrystalline lithium iron phosphate powder by adopting iron hydroxide colloid, which comprises the steps of: with Fe(OH)3 colloid as a raw material, adding a lithium source, a phosphorus source and an organic carbon source in the colloid, powerfully and uniformly stirring and drying in vacuum at low temperature to form a uniform nano precursor containing lithium, iron, phosphorus and carbon; and placing in a crucible and raising the temperature to 500-800 DEG C in a muffle furnace protected by inert atmosphere, preserving the temperature for 2-24h, cracking the organic carbon source into carbon under the inert atmosphere, reducing ferric iron into ferrous iron by the carbon to form carbon wrapped lithium iron phosphate, naturally cooling to room temperature, and then grinding or crushing to obtain the nanocrystalline lithium iron phosphate powder. The colloid Fe(OH)3 is used as an iron source, the prepared lithium iron phosphate is of nano level, has excellent electrochemical property and low-temperature discharge property, is simple in process, and is suitable for industrialized production.

Description

Technical field: [0001] The invention relates to a method for preparing nanocrystalline lithium iron phosphate powder by using iron hydroxide colloid, and belongs to a method for preparing positive electrode materials for lithium-ion power batteries. Background technique: [0002] Olivine-type lithium iron phosphate has the advantages of safety, no pollution, wide source of raw materials, and good cycle stability. It is considered to be used in pure electric vehicles, hybrid electric vehicles, electric bicycles, electric tools, energy storage power stations, etc. The best cathode material for power batteries in the field of high power. [0003] However, pure-phase lithium iron phosphate has poor conductivity and low ionic conductivity, so that its capacity decays rapidly during high-current discharge; the diffusion rate of lithium ions has a very direct relationship with temperature, especially at low temperatures (-20°C, -40°C). , the lithium ion diffusion rate is lower, r...

AI Technical Summary

Problems solved by technology

However, using these raw materials and synthesis methods, the primary particles of lithium iron phosphate materials prepared are relatively large, and the secondary aggregates are relatively large, which is obviously not conducive to material rate discharge, low temperature discharge, etc.

[0005] Invention patent 200710013369.6 discloses a method for preparing homogeneously dispersed lithium iron phosphate nanocrystals by hydrothermal synthesis. The homogeneously dispersed lithium iron phosphate nanocrystals with a particle size of 0.2-0.5 μm are prepared, but the hydrothermal synthesis method used is limited to a small amount For the preparation of powder, if the amount of preparation is to be expanded, it is difficult to design and manufacture large-scale high-temperature and high-pressure reactors, and it is difficult to realize industrialization

[0006] The patent application number is 200810029616.6, which discloses a method for preparing nano-lithium iron phosphate materials by sol-gel method, but requires a large amount of additives and complexing agents, such as polyvinyl alcohol or octadecyltrimethylammonium bromide, lemon Acid, malic acid or tartaric acid, etc., lead to problems such as large drying shrinkage of the precursor, difficulty in industrialization, and long synthesis cycle

Images