Hydrothermal synthesis method for preparing nano-scale carbon-coated lithium iron phosphate

Abstract

The invention discloses a hydrothermal synthesis method for preparing nano-scale carbon-coated lithium iron phosphate, which belongs to the field of lithium-ion battery anode materials and comprises the following steps of: sequentially adding a phosphorus-source solution, an iron-source solution, a carbon source, a lithium-source solution and a boiling-point elevator into a reaction device in sequence, mixing, then heating to the temperature of 60-180 DEG C for reaction under inert gas, cooling after the reaction, filtering precipitates to obtain a nano-scale lithium iron phosphate precursor, and then sintering the nano-scale lithium iron phosphate precursor at the temperature of 400-600 DEG C under the protection of the mixed gas of the inert gas and hydrogen gas. The combination of lithium, iron, phosphorus and the like on a molecular level is realized by the method, and the grains of a product are quite fine and are uniformly distributed; because the boiling-point elevator is adopted, the reaction temperature and pressure of the reaction kettle are decreased; and the hydrothermal synthesis method has the advantages of simple preparation process, short flow, easiness in operational control, low reaction temperature, short time, low energy consumption and easiness in realizing large-scale industrialized production.

Description

technical field [0001] The invention belongs to the field of positive electrode materials of lithium ion batteries, and in particular relates to a preparation method of nanoscale carbon-coated lithium iron phosphate as the positive electrode material of lithium ion batteries. Background technique [0002] With the rapid development of new energy vehicles, lithium-ion batteries, especially lithium-ion batteries with lithium iron phosphate materials as the positive electrode, will be widely used in hybrid electric vehicles (HEV) and pure electric vehicles (EV). Compared with lithium-ion batteries of other cathode materials, lithium iron phosphate batteries have the advantages of long cycle life, good safety, fast charge and discharge, low cost, and no pollution. The lithium iron phosphate synthesized by known methods has the following disadvantages: (1) ferrous iron Fe in the synthesis process 2+ Easily oxidized to ferric iron Fe 3+ , it is difficult to obtain pure-phase lit...

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Problems solved by technology

The lithium iron phosphate synthesized by known methods has the following disadvantages: (1) ferrous iron Fe in the synthesis process 2+ Easily oxidized to ferric iron Fe 3+ , it is difficult to obtain pure-phase lithium iron phosphate, that is, there are many impurities, which affect the capacity; (2) the particles are coarse and uneven, and lithium ions in LiFePO 4 The speed of migration and diffusion in the medium is slow, which leads to poor ion conductivity of the active material and affects the charge and discharge speed; (3) LiFePO 4 The electrical conductor itself is low, which affects its high-rate discharge performance

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