Synthesis method of lithium difluorophosphate

Abstract

The invention relates to a synthesis method of lithium difluorophosphate, belonging to the technical field of lithium battery electrolyte. The synthesis method is characterized by comprising the following steps: respectively adding P2O5, lithium-containing inorganic salt and dried organic solvent into a closed reaction kettle at normal temperature, airtightly stirring and cooling to -50DEG C to 30DEG C, displacing the atmosphere in the kettle three times with dried inert gas, increasing the temperature to 95DEG C-105DEG C after the content of moisture in the kettle is less than 1ppm, boosting pressure to 0.7MPa-0.85MPa; then introducing POF3, reacting for 5-15 hours under stirring, wherein the reaction temperature and pressure are respectively at 60DEG C to 180DEG C, and 0.5MPa to 2.5MPa, and the molar ratio of POF3 to P2O5 to lithium-containing inorganic salt is 1 to (0-1.5) to (1-5); and then filtering to obtain a filtrate, removing solvent, and recrystallizing solid to obtain crystal. The synthesis method has mild conditions, no side reactions appear, the technology process is simple, the product is easily separated and extracted, the moisture and free chlorine values are low, and the purity of the prepared product is high.

Description

technical field [0001] The invention discloses a method for synthesizing lithium difluorophosphate, which belongs to the technical field of lithium battery electrolyte. Background technique [0002] In recent years, due to the rapid development of smart devices such as mobile phones and tablet computers, the market share of small lithium batteries has grown rapidly. In addition, the technology of electric vehicles is becoming more and more perfect, and the market demand for large lithium batteries is also gradually released. It is expected that lithium batteries will maintain growth in the next few years trend. Lithium batteries are mostly secondary batteries, and their poor stability, poor low temperature resistance, and poor cycle characteristics are the main technical difficulties in their rapid development. Research has proved that lithium difluorophosphate as an electrolyte can effectively improve the above shortcomings of lithium batteries. [0003] In the prior art, ...

AI Technical Summary

Problems solved by technology

[0004] 1) with Li 2 CO 3 and LiPF 6 Or phosphorus pentafluoride reacts to prepare lithium difluorophosphate, which will produce lithium fluoride impurities that are difficult to separate;

[0005] 2) with P 4 o 10 Solid-solid reaction with LiF to synthesize lithium difluorophosphate, the reaction is not easy to control, with many by-products and low yield;

[0007] 4) Using LiPF 6 Lithium difluorophosphate is prepared by hydrolysis. This reaction is not easy to control and will produce LiPO 4 F, HF, HPO 2 f 2 Impurities that affect battery performance, and are not easy to purify, it is difficult to obtain high-purity products;

[0008] 5) Lithium difluorophosphate was prepared by displacement reaction of organotin fluoride and lithium dichlorophosphate, but the raw material trimethyltin fluoride is not easy to obtain