High-purity difluorosulfonylimide preparation method

Abstract

The invention discloses a high-purity difluorosulfonylimide preparation method, which comprises: 1, adding a protic solution accounting for 0.1-10% of the mass of a difluorosulfonylimide crude productto the difluorosulfonylimide crude product, carrying out a thermal insulation reaction for 10 min-10 h at a temperature of 10-120 DEG C, and slowly introducing HF gas accounting for 0-10% of the massof the difluorosulfonylimide crude product during the thermal insulation; and 2, distilling the difluorosulfonylimide obtained in the step 1 to obtain the high-purity difluorosulfonylimide with a chlorine ion content of less than 20 ppm. Compared with the conventional direct distillation and rectification schemes, the method of the present invention has the following characteristics that the chemical treatment method of selective decomposition is adopted, the physical separation is supplemented, and the difference in the boiling points of each substance in the system after the treatment is high, such that the separation effect of the scheme is significant, the impurity chlorine ion content in the product difluorosulfonylimide can be reduced to less than 20 ppm, and the raw material purityrequirements in the preparation of lithium bis(fluorosulfonyl)imide for subsequent electrolytic solutions can be met.

Description

technical field [0001] The invention relates to the field of preparation of difluorosulfonimide, in particular to a preparation method of high-purity difluorosulfonimide. Background technique [0002] Lithium difluorosulfonyl imide (LiFSI) is a newly developed electrolyte salt for electric vehicle power battery electrolyte. Compared with the traditional commercially used lithium hexafluorophosphate electrolyte salt, it has the characteristics of high conductivity and high thermal stability. Making it more suitable for electric vehicle applications that require high power and good high and low temperature performance. [0003] The conventional synthetic method of difluorosulfonimide lithium is to synthesize dichlorosulfonimide first, usually adopting sulfur oxychloride, chlorosulfonic acid and sulfamic acid heating reaction preparation (Beran M., Prihoda J, Z. Anorg. Allg. Chem., 2005,631 (1): 55- 59), or prepared by heating reaction of chlorosulfonic acid and chlorosulfon...

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Problems solved by technology

[0005] However, even if conditions such as excessive fluorinating agent, addition of catalyst, high-temperature fluorination, and prolonged reaction time are used to strengthen the fluorination conversion, the conversion of chloride to difluoride is difficult to carry out completely, and there will be dichlorosulfonimide or a Fluorine-chlorosulfonimide residues, usually the chlorine ion detection result will be above 10000ppm, the above-mentioned patents use distillation or rectification to purify

Since the boiling point of fluorochlorosulfonimide and difluorosulfonimide is close, the detection result of chloride ion after distillation and separation will be above 1000ppm, which is difficult to meet the purity requirements of lithium difluorosulfonimide for subsequent preparation of electrolyte , and the use of rectification to purify will greatly increase equipment investment and reduce product yield, increase the difficulty of operation, and even so, it is difficult to control the chloride ion impurity content below 20ppm, so it needs Considering the elimination plan of these impurities in the middle, it increases the complexity of the salt formation process

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