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Lithium hexafluorophosphate purification method

A technology of lithium hexafluorophosphate and a purification method, which is applied in the field of lithium hexafluorophosphate purification, can solve the problems of inability to reduce acid and metal impurities, reduce the performance of lithium-ion batteries, and have no purification, and achieve easy promotion and use, good social value and economic value, and production low cost effect

Inactive Publication Date: 2017-08-18
DO FLUORIDE CHEM CO LTD
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

Lithium hexafluorophosphate is generally prepared from anhydrous hydrogen fluoride, phosphorus pentoxide and lithium fluoride. The finished product inevitably contains hydrogen fluoride impurities. In addition, lithium hexafluorophosphate is easy to absorb water and undergo hydrolysis reaction, decomposing into insoluble lithium oxyfluorophosphate compounds, and these Impurities in the use of lithium-ion batteries will reduce the performance of lithium-ion batteries, so how to obtain high-purity lithium hexafluorophosphate with high purity, low free acid and low moisture is an urgent problem to be solved at present
[0003] Chinese patent (publication number CN 1850593A) discloses a method for purifying lithium hexafluorophosphate. After the mixed gas of phosphorus pentafluoride and hydrogen fluoride is purified, it is passed into the drying equipment of lithium hexafluorophosphate, so that the fluorine entrained in phosphorus pentafluoride and lithium hexafluorophosphate in the preparation process Lithium oxide and lithium oxyfluoride LiPO x f y React and convert into lithium hexafluorophosphate, so that lithium hexafluorophosphate can be purified, but this method cannot reduce the acid and metal impurities contained in the lithium hexafluorophosphate crystal or attached to the surface
This method requires repeated crystallization to remove inorganic and organic impurities in lithium hexafluorophosphate, and there is no purification of hydrogen fluoride impurities remaining in lithium hexafluorophosphate

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0025] The purification method of lithium hexafluorophosphate in this embodiment, the lithium hexafluorophosphate to be purified is a large-scale production product, and the quality inspection results are: the product purity is greater than 99.9%, the product free acid (calculated by HF) is 80ppm, the moisture (by Karl Fischer method) is 5ppm, and the alkali metal ion content (in terms of K, Na) 2ppm, heavy metal ion content (in terms of Fe) 2ppm, and insoluble content 220ppm; the purification operation is as follows:

[0026] 1) Add 150mL of diethyl ether to a 500mL reaction vessel in a glove box filled with nitrogen and have sufficient operating space, use a refrigerator to lower the temperature of the ether to 15°C, start stirring, and add 90g of lithium hexafluorophosphate to be purified for dissolution. Measure the temperature of the system with 5g, keep the temperature of the dissolution process at 10°C to 25°C, continue to stir for 20 minutes after adding to complete the...

Embodiment 2

[0030] In this example, diethyl ether was added to 35 mL of the mother liquor obtained after crystallization in Example 1 to obtain 100 mL of mixed liquid, and 45 g of the large-scale lithium hexafluorophosphate product was taken. The quality inspection results were: the product purity was greater than 99.9%, and the product free acid (calculated as HF) was 75 ppm , moisture (by Karl Fischer method) 5ppm, alkali metal ion content (calculated by Ka, Na) 2ppm, heavy metal ion content (calculated by Fe) 2ppm, insoluble matter content 230ppm;

[0031] With above-mentioned mixed liquor as organic solvent, carry out purifying operation by the process parameter among the embodiment 1, obtain 45g lithium hexafluorophosphate product, test result is: product purity is greater than 99.9%, product free acid (in HF) 20ppm, moisture (in Karl Fischer Method) 3ppm, alkali metal ion content (calculated by Ka, Na) 1ppm, heavy metal ion content (calculated by Fe) 1ppm, insoluble matter content 18...

Embodiment 3

[0033] The purification method of lithium hexafluorophosphate in this embodiment, the lithium hexafluorophosphate to be purified is a large-scale production product, and the quality inspection results are: the product purity is greater than 99.9%, the product free acid (calculated by HF) is 90ppm, the moisture (by Karl Fischer method) is 6ppm, and the alkali metal ion content (in terms of K, Na) 2ppm, heavy metal ion content (in terms of Fe) 2ppm, and insoluble content 200ppm; the purification operation is as follows:

[0034] 1) In a glove box filled with nitrogen and with sufficient operating space, add 150 mL of dimethyl carbonate to a 500 mL reaction vessel, use a refrigerator to lower the temperature of dimethyl carbonate to 20 ° C, start stirring, and add 80 g of dimethyl carbonate to be purified Dissolve lithium hexafluorophosphate, measure the temperature of the system every time 5g is added, keep the temperature of the dissolution process at 15°C to 40°C, continue to s...

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Abstract

The invention relates to a lithium hexafluorophosphate purification method, and belongs to the technical field of a lithium ion battery. The lithium hexafluorophosphate purification method comprises the following steps that (1) under the protection atmosphere, an organic solvent is added into lithium hexafluorophosphate to be purified for dissolution; filtering is performed to obtain filter liquid; (2) silazane is added into the filter liquid for performing deacidification reaction; crystallization is performed to obtain crystals; drying is performed; the finished product is obtained. The purification method disclosed by the invention has the advantages that an ether solvent, a carbonic ester type solvent or acetonitrile is used as the organic solvent for purifying the lithium hexafluorophosphate crude products; insoluble substances in the lithium hexafluorophosphate are removed; then, the silazane is added to act with HF acid remained in the lithium hexafluorophosphate crude products for removing free acid; metal impurities are removed through the recrystallization process. The lithium hexafluorophosphate purification method has the advantages that the lithium hexafluorophosphate with poor quality is treated; acid and metal impurities attached at the surface or blended inside the lithium hexafluorophosphate crystals can be effectively removed; the insoluble substance content is reduced; the quality of the lithium hexafluorophosphate product is improved.

Description

technical field [0001] The invention relates to a method for purifying lithium hexafluorophosphate, which belongs to the technical field of lithium ion batteries. Background technique [0002] In the past ten years, the rapid development of the lithium battery industry has driven the rapid development of the upstream industry, and the demand for lithium-ion battery electrolytes has continued to increase. Lithium hexafluorophosphate, as an internationally recognized excellent electrolyte, is one of the key core materials for manufacturing lithium-ion batteries. The cycle life, rate charge and discharge performance, and high and low temperature performance of lithium-ion batteries are all directly related to the quality of lithium hexafluorophosphate electrolyte. Impurities in the electrolyte are The performance of the positive and negative electrodes will be greatly affected during the operation of the battery. Lithium hexafluorophosphate is generally prepared from anhydrous...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): C01D15/00
CPCC01D15/005C01P2006/80
Inventor 李金波王艳君闫春生李恺李媛媛王选李洁董保京
Owner DO FLUORIDE CHEM CO LTD
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