Preparation and purification method of lithium hexafluorophosphate

Abstract

The invention discloses a preparation and purification method of lithium hexafluorophosphate. The method comprises the following steps of (1) preparing a lithium hexafluorophosphate solution by using PF5, LiF and hydrogen fluoride; (2) removing a trace amount of insoluble impurities from the lithium hexafluorophosphate solution obtained in the step (1), transferring the solution o an evaporation crystallizer, and heating and evaporating one part of hydrogen fluoride; and (3) stopping evaporating until the liquid level is 1 / 3 to 2 / 3 of initial liquid level, cooling to -20 DEG C to -40 DEG C according to a temperature gradient and filtering to obtain a crude product of lithium hexafluorophosphate and purifying to obtain a target product lithium hexafluorophosphate. The preparation method is simple in process and low in cost, and the obtained product is high in purity.

Description

technical field [0001] The invention belongs to the technical field of power lithium ion battery manufacturing, in particular to a method for preparing and purifying electrolyte salt 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. It is used in well-known products such as mobile phones, notebook computers, small cameras, and electric vehicles. With the industrialization of electric vehicles, the amount of use is bound to increase. The application shows that lithium-ion battery is an ideal small green power source. Lithium hexafluorophosphate is the key core material for manufacturing lithium-ion batteries, and is the most widely used electrolyte lithium salt in commercial lithium-ion batteries. It has excellent electrochemical properties, good ion conductivity, and good sol...

AI Technical Summary

Problems solved by technology

[0003] As an important electrolyte salt of lithium ion battery electrolyte, lithium hexafluorophosphate requires high purity (usually not less than 99.5%), and impurities such as water, alkali metals, heavy metals and other impurities such as PCl 3 and POCl 3 The content must be strictly controlled, otherwise it will lead to increased internal resistance of the battery, rapid decay of battery capacity, shortened cycle life, and even affect the safety of the battery

[0006] The above-mentioned technology has disadvantages such as low crystallization efficiency; two drying treatments are required, which takes a long time, time-consuming and labor-intensive; the moisture content needs to be further reduced.