A kind of preparation method of lithium iron phosphate cathode material

Abstract

The invention discloses a method for preparing a lithium iron phosphate positive material. Aiming at overcoming the conventional modification defects of a lithium iron phosphate material, a certain amount of carbon source is added into a synthesized precursor, carbon source gas and silicon source gas are introduced in a sintering process, a SiC coating layer is uniformly deposited on the surface of the lithium iron phosphate material through a chemical vapour deposition method, and thus the lithium iron phosphate material with the uniform SiC / C coating layer on the surface is prepared. In a synthesis process, the added amount of carbon source in the precursor, and the gas inlet pressures and flows and the vapour deposition time of the carbon source gas and the silicon source gas in a vapour deposition process are regulated, so that the lithium iron phosphate material with the uniform C / SiC coating layer on the surface is obtained. The lithium iron phosphate positive material has small primary particle size, is provided with the uniform and compact C / SiC coating layer on the surface and has high tap density, better multiplying power charging and discharging performance and excellent processability, so that the lithium iron phosphate positive material has broad application prospect in the field of power lithium ion batteries.

Description

technical field [0001] The invention relates to the fields of electrochemical material preparation and new energy, in particular to a preparation method of lithium iron phosphate cathode material. Background technique [0002] With the increasing energy crisis, the whole world is looking for new renewable resources. Renewable resources such as solar energy, wind energy, tidal energy, geothermal energy, etc. have regional and temporal characteristics. To make full use of these resources, smart grids or large-scale energy storage systems are required. Lithium-ion batteries have promising application prospects as energy storage potentials. On the other hand, the depletion of petrochemical energy forces people to develop hybrid electric or pure electric vehicles, and its core component battery has become a research focus. Compared with other batteries, lithium-ion is favored for its high energy density, good safety and long service life. [0003] Lithium iron phosphate materi...

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Problems solved by technology

The smaller the crystal particle radius, the shorter the solid phase diffusion process of lithium ions in the ion, and the easier the intercalation and extraction of lithium ions; (2) element doping, introducing heteroatoms into the material lattice to improve the electrical conductivity of the material, but Its feasibility and working mechanism are still unclear at present, and the effect is not obvious, and the capacity will decrease with the increase of element doping amount; (3) doping with conductive agent can improve the electronic conductivity of the material, and most of them use carbon Coating technology, due to the complex form of carbon materials, the tap density of most carbon-coated lithium iron phosphate materials will be greatly reduced, and the processing performance will be affected to a certain extent

[0005] There are many studies on the modification of lithium iron phosphate materials, but it has not been found that adding carbon source to the precursor combined with vapor deposition of SiC during sintering to synthesize iron phosphate with small particle size and tight SiC / C carbon coating Research on Lithium Materials

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