METHOD FOR DRYING AND PURIFYING LiFSI

A method for drying and purifying a lithium bis(fluorosulfonyl)imide salt in solution in an organic solvent S1, the method including the following steps: a) adding deionised water to dissolve and extract the lithium bis(fluorosulfonyl)imide salt, forming an aqueous solution of the salt; b) extracting the lithium bis(fluorosulfonyl)imide salt from the aqueous solution, using an organic solvent S2, the step being repeated at least once; c) concentrating the lithium bis(fluorosulfonyl)imide salt by evaporating the organic solvent S2 and the water, in a short-path thin-film evaporator, under the following conditions: temperature of 30° C. to 95° C., pressure of 10mbar abs to 5 mbar abs, residence time no longer than 15 min; and d) optionally crystallising the lithium bis(fluorosulfonyl)imide salt. Also, a composition made of lithium bis(fluorosulfonyl)imide salt, and the uses thereof in Li-ion batteries.