Method for preparing carbonate solution of alkali metal or alkaline earth metal bis(fluorosulfonyl)imide

A method for preparing a carbonate solution of an alkali metal or alkaline earth metal bis(fluorosulfonyl)imide, the method comprising:

• 1) inserting an ammonium bis(fluorosulfonyl)imide and an alkali metal salt or an alkaline earth metal salt into a reactor under nitrogen, adding a carbonate and an organic solvent other than the carbonate, and performing stirring at a room temperature for 1 to 7 hours;
• and
• 2) filtering the completed reaction solution of step 1) to obtain a filtrate and concentrating the filtrate under reduced pressure at 30 to 90° C. to remove the organic solvent other than the carbonate.