Preparation method of vanadium oxide and lithium iron phosphate composite materials with high tap density

Abstract

The invention discloses a preparation method of vanadium oxide and lithium iron phosphate composite materials with a high tap density. The method comprises the following steps: (1) preparing a lithium iron phosphate precursor; (2) preparing the vanadium oxide and lithium iron phosphate composite materials; and (3) molding processing, sintering under a temperature of 500-800 DEG C in an atmosphere of nitrogen, crushing the sintered materials, and sieving by a sieve of 100-400 meshes to obtain the vanadium oxide and lithium iron phosphate composite materials with the high tap density. The method can greatly improve diffusion capacity of lithium ion among particles, and thus improve power performance of the lithium iron phosphate. Spherical-like precursors are compacted and sintered after a drying processing of a secondary mixing, and thus pores among particle are reduced, components of the precursors are combined tightly, and the reaction is carried out adequately. The sintered lithium iron phosphate particles are round in surface morphology, and can effectively improve tap density of the materials.

Description

technical field [0001] The invention mainly relates to a preparation method of a composite material, in particular to a preparation method of a high tap density vanadium oxide and lithium iron phosphate composite material. Background technique [0002] In recent years, new energy vehicles have attracted more and more people's attention. The Ministry of Industry and Information Technology's "Development Plan for Energy Conservation and New Energy Vehicle Industry" has been formulated and will be announced soon—a ten-year investment of 100 billion. New energy vehicles are impressively listed among the seven strategic emerging industries in "The Decision to Develop Strategic Emerging Industries". As an important part of new energy vehicles - power lithium-ion batteries will also usher in a spring of development; [0003] Due to its excellent performance, lithium iron phosphate has become the preferred cathode material for power lithium-ion batteries for electric vehicles. The ...

AI Technical Summary

Problems solved by technology

However, since carbon is only a good conductor of electrons, Li + The carbon-coated lithium iron phosphate particles can only diffuse through the interstitial position of the carbon layer or the surface not covered by the carbon layer, while Li + The intercalation and deintercalation in the lithium iron phosphate crystal can only pass through the (010) surface of the olivine crystal structure, and the path of the deintercalation of lithium is similar to a one-dimensional structure. Therefore, to some extent, improper carbon coating treatment will inevitably affect Li + effective diffusion, resulting in a polarization effect, affecting the performance of the material

The metal ion doping process replaces the lithium site or iron site of lithium iron phosphate with high-valent metal ions to change its lattice constant microscopically, so as to achieve the effect of optimizing the transmission path of lithium ions. At the same time, the electronic compensation effect can improve the volume of the material. Phase conductivity, but in the actual industrialization process it is difficult to accurately control the doping position of the metal ion on the iron position or the lithium position, and when the doped metal ion occupies the lithium position, a part of the capacity of the material will be sacrificed, causing the material The gram capacity drops

Tap density can be said to be the biggest shortcoming of lithium iron phosphate, which also limits its application range to a certain extent

In the process of preparing lithium iron phosphate by means of solid-state reaction, most of them involve carbon coating or carbothermal reduction technology. Since the carbon material hinders the growth of lithium iron phosphate grains during the reaction process, and the organic matter Pyrolytic carbon mostly has a loose and porous form, both of which reduce the tap density of lithium iron phosphate to a certain extent

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