Method for preparing carbon-coated spherical nano lithium iron phosphate by liquid phase method

Abstract

The invention discloses a method for preparing carbon-coated spherical nano lithium iron phosphate by a liquid phase method. According to the method, a lithium iron phosphate powder body with an olivine structure is quickly produced in a normal pressure liquid phase, the nano lithium iron phosphate powder obtained by the reaction is mixed with an organic carbon source such as glucose, the resultant product can be carbonized and spherized at high temperature within a very short time under the protection of inert atmosphere to obtain the carbon-coated spherical nano lithium iron phosphate with a small and uniform particle size, and the particle size range is 50nm to 300nm. The technical scheme of the invention is as follows: a certain-concentration mixed aqueous solution of ferrous salt and phosphoric acid is prepared with an equimolar ratio, and is placed in a reactor, a high-boiling-point polar organic solvent such as dimethyl sulfoxide and crystal growth inhibitor, such as polyacrylamide, of 0.5-3% are added, and the volume ratio of the aqueous solution to the high-boiling-point polar organic solvent is 0.5-2:1; under stirring, a lithium hydroxide solution with a certain concentration is added slowly until the pH value of a reaction solution is 6 to 7, and then the solution is heated to the boiling point, and reacts under reflux for 0.5 to 3h; the product is conventionally filtered, washed, and dried in a vacuum to obtain a nano-lithium iron phosphate powder body; and then the generated nano-lithium iron phosphate powder and the organic carbon source such as the glucose are mixed and placed in a high-temperature furnace in which inert gas is introduced to be used as protective gas, and under the condition that the temperature is controlled between 500 and 700 DEG C, the resultant product is crystallized and spheroidized for 1 to 5h, and is cooled and then pulverized to obtain the product provided by the invention. The product provided by the invention is used for a cathode material of lithium-ion batteries.

Description

technical field [0001] The invention belongs to a preparation method of a positive electrode material of a lithium ion battery, in particular to a method for directly preparing carbon-coated nanometer lithium iron phosphate powder under normal pressure liquid phase conditions. Background technique [0002] The theoretical capacity of lithium iron phosphate is 170mAh / g, and the discharge voltage is 3.4V. It has excellent safety performance and cycle performance, and the material has a wide range of raw materials, low price, and no pollution to the environment. It is considered to be a power lithium-ion battery with great potential. Materials have become a hot spot in research and development in recent years. However, lithium iron phosphate itself also has some defects. The first is that its special structure hinders the deintercalation rate of lithium ions; the second is that the electronic conductivity is poor, resulting in poor high-rate discharge performance; the third is ...

AI Technical Summary

Problems solved by technology

This method takes a long time to treat the precursor and the process is complicated. Since the precursor is not lithium iron phosphate forming an olivine structure, it still needs a long follow-up high temperature treatment.

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