Preparation method of nano lithium iron phosphate/carbon porous anode material with high-rate performance

Abstract

The invention discloses a nano lithium iron phosphate / porous carbon anode material with high-rate performance and a preparation method thereof. The nano lithium iron phosphate / porous carbon anode material is suitable for power batteries. Different from a process for preparing a porous lithium iron phosphate material by using a hydrothermal synthesis method, a composite nano lithium iron phosphate / carbon porous material is successfully prepared by using an improved solid phase synthesis method. The preparation method comprises the following steps of: grinding and dispersing an organic high-molecular pore-foaming agent and an iron-compound to obtain a uniform mixture; then sequentially adding a phosphorous compound and a lithium compound into a mixing system; ball-milling the mixture for a certain period of time; moving an obtained thick intermediate product into a closed reactor; heating the closed reactor to 80-140 DEG C; keeping the closed reactor at a constant temperature for a certain period of time; finally drying a reaction product, and carrying out a sintering process at 600-750 DEG C to prepare the nano lithium iron phosphate / porous carbon anode material. The preparation method is simple and good in product reproducibility and has the advantages of excellent electronic conductivity and ionic conductivity, high reversible cycle capacity and good high-rate performance.

Description

technical field [0001] The invention relates to a positive electrode material of a secondary lithium ion battery, in particular to a high rate performance nanometer lithium iron phosphate / carbon porous positive electrode material and a preparation method thereof. Background technique [0002] Commercial lithium-ion secondary batteries have been widely used in electronic products such as mobile phones, notebook computers, and digital cameras. What is even more exciting is that, as a clean energy source, lithium-ion batteries are regarded as the best power source for new electric vehicles and hybrid vehicles. Therefore, based on the application of power batteries, improving the electrochemical characteristics of lithium-ion batteries under high-rate conditions is a hot spot for current and future research and development. [0003] The improvement of the performance of lithium-ion batteries depends to a large extent on the development and application of high-performance positi...

AI Technical Summary

Problems solved by technology

However, in LiFePO 4 In the crystal structure, due to the adjacent FeO 6 Octahedrons are connected by common vertices, therefore, their electronic conductivity is low; in addition, PO 4 Tetrahedral on FeO 6 between octahedrons, which hinders the Li + Diffusion movement; and stable PO 4 The tetrahedron makes Li + The free volume to move is small, so that the de-intercalation motion is affected

In summary, based on the microstructure characteristics of pure-phase olivine-structured lithium iron phosphate, its electronic conductivity and ionic conductivity are extremely poor, which hinders the charge transfer of the material when it is charged and discharged under high-rate conditions. Insufficient intercalation / extraction depth will lead to a decrease in capacity, and more seriously, the obstruction of charge transfer will lead to an increase in the internal resistance of the battery, which will intensify the capacity fading of the material

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