Preparation method for yttrium iron fluoride doped lithium manganese phosphate-carbon composite cathode material

Abstract

The invention relates to a preparation method for a yttrium iron fluoride doped lithium manganese phosphate--carbon composite cathode material. The chemical formula of the yttrium iron fluoride doped lithium manganese phosphate is LiMn1-x-y FexYyP1-zFzO4, wherein the x equals to 0.2-0.3; the y equals to 0.01-0.025; the z equals to 0.05-0.15.The preparation method comprises the following steps: (1) preparing the yttrium iron fluoride doped lithium manganese phosphate; (2) preparing conductive carbon dispersion; mixing ytterbium magnesium doped lithium manganese phosphate precursor with the conductive carbon dispersion to obtain a mixture; after ball milling and drying, placing the mixture in a mixed atmosphere of argon and acetylene; sintering and obtaining the yttrium iron fluoride doped lithium manganese phosphate-carbon composite cathode material; according to the invention, rare earth element Y and transitional element Fe are doped in the lithium manganese phosphate composite material, so as to replace part of M n; F is doped to replace part of P for modification and improvement to the electronic conductivity and physical activity; then, coating carbon black and a carbon nanotube mixed carbon network wrap the surface of the lithium manganese phosphate composite cathode material so as to further improve the electrical conductivity and cycling stability.

Description

Technical field [0001] The invention relates to a preparation method of yttrium-iron-fluorine-doped lithium manganese phosphate-carbon composite cathode material. Background technique [0002] At present, the anode materials of lithium-ion batteries mainly include lithium cobalt oxide, lithium manganese oxide, ternary materials and transition metal phosphates. Lithium cobalt oxide was first commercially used as a battery cathode material, but the material has high production costs, poor thermal stability, large environmental pollution, and poor safety performance. LiCoO 2 Cathode materials cannot meet many requirements of electric vehicles for power batteries. The lithium iron phosphate cathode material developed in recent years has become the most promising lithium ion power battery material due to its long cycle life, excellent safety performance, good high temperature performance and high rate discharge performance. Although the lithium iron phosphate cathode material h...

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Problems solved by technology

[0004] However, the electrode potential of lithium manganese phosphate relative to Li is 4.1V, which is much higher than the 3.4V voltage platform of lithium iron phosphate, and under this voltage platform, the conductivity of existing positive electrode materials is very poor, coupled with its electrochemical capacity Low, poor high temperature performance limits its application