Preparation method of lithium hexafluorophosphate

Abstract

The invention relates to a preparation method of lithium hexafluorophosphate. The preparation method comprises the following steps of: (1) distilling to obtain hydrogen fluoride liquid of which the purity is over 99.99 weight percent; (2) reacting the high-purity hydrogen fluoride liquid with phosphorus pentachloride to obtain mixed gas of the phosphorus pentafluoride and hydrogen chloride; (3) introducing the mixed gas of the phosphorus pentachloride and the hydrogen chloride into hydrogen fluoride and lithium fluoride, reacting at a certain temperature and under certain pressure to obtain solution of lithium hexafluorophosphate, exhausting hydrogen chloride gas at regular time, and absorbing by using water to prepare byproduct hydrochloric acid; and (4) crystallizing and separating, namely filtering the solution of lithium hexafluorophosphate, delivering filtrate into a crystallizing slot, separating the lithium hexafluorophosphate out at the temperature of between -70 and 80 DEG C, filtering, and performing primary drying and secondary drying to obtain a lithium hexafluorophosphate product, wherein the residual hydrogen fluoride gas is displaced by nitrogen. The preparation method has readily available raw materials and is easy to operate, the purity of the obtained lithium hexafluorophosphate product is over 99.9 percent, the moisture is lower than 10ppm, and the production requirements of lithium ion electrolytic cells are met.

Description

technical field [0001] The invention relates to a preparation method of lithium hexafluorophosphate. Background technique [0002] Lithium-ion batteries have outstanding advantages such as high working voltage, high energy density (light weight), low self-discharge rate, no memory effect, long cycle life and no pollution. In recent years, it has quickly occupied many fields with its incomparable advantages over other batteries, and is widely used in well-known mobile phones, notebook computers, small cameras, electric vehicles and other products. With the industrialization of electric vehicles, the amount of lithium-ion batteries is bound to increase. The application shows that lithium-ion battery is an ideal small green power source. [0003] Lithium hexafluorophosphate, as an important electrolyte salt of lithium-ion battery electrolyte, requires high purity (usually not less than 99.5%), and the content of impurities such as water, alkali metals, heavy metals and other ...

AI Technical Summary

Problems solved by technology

[0003]Lithium hexafluorophosphate is an important electrolyte salt of lithium-ion battery electrolyte, which requires high purity (usually not less than 99.5%), and impurities such as water , the content of alkali metals, heavy metals and other impurities such as PCl3 and POCl3 must be strictly controlled, otherwise the internal resistance of the battery will increase, the battery capacity will decay quickly, the cycle life will be shortened, and even the safety of the battery will be affected