Preparation method of potassium bis(fluorosulfonyl)imide

The invention relates to the field of chemical synthesis, in particular to a preparation method of potassium bis(fluorosulfonyl)imide. The preparation method comprises the following steps: 1) carrying out a reaction between chlorosulfonic acid and chlorosulfonyl isocyanate to obtain bis(chlorosulfonyl)imide in the presence of a catalyst; 2) carrying out a reaction between the bis(chlorosulfonyl)imide and hydrogen fluoride in the presence of a catalyst to obtain bis(fluorosulfonyl)imide; 3) carrying out a reaction between the bis(fluorosulfonyl)imide and an alkaline potassium compound to obtain the potassium bis(fluorosulfonyl)imide. According to the preparation method provided by the invention, the chlorosulfonic acid and the chlorosulfonyl isocyanate can be used as raw materials in the first step, so that generation of waste gases such as SO2, HCl and the like is avoided, and thus a requirement on environment friendliness can be met better.