CN1850592A

CN1850592A - Method for preparing potassium hexafluoro phosphate

Info

Publication number: CN1850592A
Application number: CN 200610013957
Authority: CN
Inventors: 赵庆云; 宁延生; 郭西凤
Original assignee: TIANJIN CHEMICAL RESEARCH & DESIGN INST
Current assignee: TIANJIN CHEMICAL RESEARCH & DESIGN INST
Priority date: 2006-05-30
Filing date: 2006-05-30
Publication date: 2006-10-25

Abstract

The invention relates to Li ion battery technique, a lithium hexafluoro- phosphate preparing method, characterized in comprising the process steps of: using easy sublimation property of phosphorus pentachloride, heating and sublimating it to remove nonvolatile components, refining industrial anhydrous hydrogen fluoride to remove water and heavy metal impurities; reacting them with each other to prepare mixed gas of phosphorus pentachloride and hydrogen chloride; leading the mixed gas into anhydrous hydrogen fluoride of lithium fluoride, reacting, crystallizing and separating and drying to obtain pure lithium hexafluoro-phosphate.

Description

Preparation method of lithium hexafluorophosphate

Technical Field

The invention relates to a lithium ion battery technology, in particular to a preparation method of lithium hexafluorophosphate.

Background

Lithium hexafluorophosphate is an important electrolyte salt of lithium ion battery electrolytes. The process for the preparation of lithium hexafluorophosphate generally comprises two processes.

First method is to react red phosphorus with fluorine gas to prepare PF₅And reacting the gas with an anhydrous hydrogen fluoride solution of lithium fluoride, and crystallizing, separating and drying to obtain a lithium hexafluorophosphate product. As disclosed in Japanese patent laid-open No. 2001-122604; 122605, respectively; 163610.

and secondly, reacting phosphorus pentachloride with anhydrous hydrogen fluoride to generate mixed gas of the phosphorus pentafluoride and hydrogen chloride, reacting with anhydrous hydrogen fluoride solution of lithium fluoride, and reacting, crystallizing, separating and drying to obtain the lithium hexafluorophosphate product. Such as Japanese patent laid-open No. 5-279003; japanese patent laid-open No. 4-175216.

In the preparation process of lithium hexafluorophosphate, the raw materials such as phosphorus pentachloride, anhydrous hydrogen fluoride, lithium fluoride and the like usually containHas certain impurities such as water, alkali metal and heavy metal ions, especially phosphorus pentachloride, which is easy to absorb moisture to cause deliquescence, and contains PCl₃、POCl₃And if the impurities are brought into a lithium hexafluorophosphate product, the electrolyte prepared from the product and applied to a lithium ion battery can cause the increase of the internal resistance of the battery, the attenuation of the capacity of the battery is fast, the cycle life is shortened, and even the safety of the battery is influenced.

There are many reports on a method for refining and removing harmful substances such as lithium oxyfluoride phosphate LiPOxFy compound in lithium hexafluorophosphate product: for example, Japanese patent laid-open No. 60-251109 proposes a method of removing water from a lithium hexafluorophosphate solution by introducing fluorine gas into the lithium hexafluorophosphate solution. The principle is as follows:

，

OF₂the boiling point is-145 ℃ and is easy to volatilize.

Japanese patent application laid-open No. 2000-154009 proposes adding a certain amount of PCL to lithium hexafluorophosphate product₅And anhydrous HF, so that the LiPOxFy compound in the LiPOxFy is converted into lithium hexafluorophosphate. The principle is as follows:

，

。

japanese patent laid-open No. 58-161910 proposes a method of recrystallizing lithium hexafluorophosphate from Ethylene Carbonate (EC).

Japanese patent laid-open No. 59-81870 proposes a method of recrystallizing lithium hexafluorophosphate in ethylene glycol dimethyl ether (DME).

Japanese patent laid-open No. 5-279003 proposes to use PCL₅PF is generated after reaction with anhydrous hydrogen fluoride₅And HCl gas, cooling (-50 deg.C) to remove POF₃A method for producing impurities.

The above methods are all fineAnd removing harmful impurities of lithium hexafluorophosphate. But using F₂Not only has high toxicity, but also has high price, which increases the manufacturing cost of the product.

Lithium hexafluorophosphate is recrystallized in an organic solvent, and a certain amount of organic solvent is still carried in a recrystallized product by utilizing the property that the lithium hexafluorophosphate has different solubilities at different temperatures, so that the purity of the productis influenced.

PF removal using lower temperature cooling₅And POF in HCl gas₃Impurities but not other harmful impurities, and are costly.

Disclosure of Invention

The invention aims to provide a preparation method of lithium hexafluorophosphate for effectively removing harmful impurities, which is characterized by comprising the following process steps:

1. the phosphorus pentachloride product is heated to sublimate to remove nonvolatile components by utilizing the easy sublimation property of the phosphorus pentachloride product, and simultaneously, a certain amount of chlorine gas is introduced into the phosphorus pentachloride product, so that phosphorus oxychloride and phosphorus trichloride in the phosphorus pentachloride product are converted into phosphorus pentachloride, and the purity of the phosphorus pentachloride is improved;

2. rectifying, refining and purifying the industrial anhydrous hydrogen fluoride to remove water and heavy metal impurities in the industrial anhydrous hydrogen fluoride;

3. reacting the refined phosphorus pentachloride with an anhydrous hydrogen fluoride solution to prepare a mixed gas of the phosphorus pentafluoride and hydrogen chloride;

4. dissolving anhydrous lithium fluoride in an anhydrous hydrogen fluoride solution to form an anhydrous hydrogen fluoride solution of lithium fluoride;

5. introducing the mixed gas of phosphorus pentafluoride and hydrogen chloride into anhydrous hydrogen fluoride solution of lithium fluoride, and reacting, crystallizing, separating and drying to obtain a pure lithium hexafluorophosphate product.

Detailed description of the preferred embodiments

The invention is further illustrated by the following examples.

The chemical formula used is:

LiF- -lithium fluoride;

HF- - - -anhydrous hydrogen fluoride;

PCl₅-phosphorus pentachloride;

POCl₃-phosphorus oxychloride;

HCl- - -hydrogen chloride;

PF₅-phosphorus pentafluoride;

LiPF₆-lithium hexafluorophosphate;

example 1:

adding 1000g of phosphorus pentachloride into a 10L closed reactor with stirring and jacket heat preservation, heating to 160 deg.C while stirring, maintaining the temperature, sublimating phosphorus pentachloride, introducing sublimed gas into another 5L reactor with stirring and cooling jacket, and charging 10gCl₂Cooling is performed in the cooling apparatus of (1).

After sublimation is finished, 600g of anhydrous hydrogen fluoride with the water content of less than 10ppm after rectification and purification is slowly added into the second reactor to react with phosphorus pentachloride to generate PF₅And HCl gas mixture.

In a third 3L reactor with stirring and cooling jacket, 110g of purified lithium fluoride were dissolved in 2000g of anhydrous hydrogen fluoride to form an anhydrous hydrogen fluoride solution of LiF, which was stirred with the introduced PF₅And reacting with HCl gas, and cooling, crystallizing, filtering and drying after the reaction is finished to obtain 200g of lithium hexafluorophosphate product. And (3) detection results: the product had 100ppm free acid (as HF), 5ppm moisture (Calf method), 2ppm alkali metal ion (as K, Na), 2ppm heavy metal ion (as Fe), and 500ppm insoluble in DME.

Example 2:

2500g of the filtered mother liquor from example 1 was crystallized and 110g of purified lithium fluoride and anhydrous hydrogen fluoride were added under stirring to form an anhydrous hydrogen fluoride solution of LiF. The reaction procedure in example 1 was repeated. 600g of lithium hexafluorophosphate product was obtained. And (3) detection results: the product had a free acid (as HF) of 98ppm, moisture (Karl Fischer method) of 5ppm, alkali metal ion content (as K, Na) of 3ppm, heavy metal ion content (as Fe) of 2ppm, and 500ppm of insoluble materials in DME.

Comparative example 1:

phosphorus pentachloride in example 1 was not purified by sublimation, and other reaction processes were the same. 210g of lithium hexafluorophosphate product are obtained. And (3) detection results: the product had a free acid (as HF) of 250ppm, moisture (Karl Fischer method) of 8ppm, alkali metal ion content (as K, Na) of 5ppm, heavy metal ion content (as Fe) of 6ppm, and 1500ppm of insoluble materials in DME.

Comparative example 2:

phosphorus pentachloride in example 2 was not purified by sublimation, and other reaction processes were the same. 280g of lithium hexafluorophosphate product was obtained. And (3) detection results: the product had a free acid (as HF) content of 280ppm, a moisture content (Karl Fischer method) of 15ppm, an alkali metal ion content (as K, Na) of 6ppm, a heavy metal ion content (as Fe) of 8ppm, and 1550ppm insoluble in DME.

Claims

1. The invention relates to a preparation method of lithium hexafluorophosphate,which is characterized by comprising the following process steps:

A. the phosphorus pentachloride product is heated to sublimate to remove nonvolatile components by utilizing the easy sublimation property of the phosphorus pentachloride product, and chlorine gas is introduced into the phosphorus pentachloride product to convert phosphorus oxychloride and phosphorus trichloride into phosphorus pentachloride, so that the purity of the phosphorus pentachloride is improved;

B. rectifying, refining and purifying industrial anhydrous hydrogen fluoride to remove water and heavy metal impurities;

C. reacting the refined phosphorus pentachloride with an anhydrous hydrogen fluoride solution to prepare a mixed gas of the phosphorus pentafluoride and hydrogen chloride;

D. dissolving anhydrous lithium fluoride in an anhydrous hydrogen fluoride solution to form an anhydrous hydrogen fluoride solution of lithium fluoride;

E. introducing the mixed gas of phosphorus pentafluoride and hydrogen chloride into anhydrous hydrogen fluoride solution of lithium fluoride, and reacting, crystallizing, separating and drying to obtain a pure lithium hexafluorophosphate product.