Processes for removing reactive solvent from lithium bis(fluorosulfonyl)imide (LiFSI) using organic solvents that are stable toward anodes in lithium-ion and lithium-metal batteries

A method of processing a lithium salt that is either a lithium bis(fluorosulfonyl) imide (LiFSI) salt or a lithium bis(trifluoromethanesulfonyl)imide (LiTFSI) salt, the method comprising:

• a reactive-solvent-reduction process that includes:
• providing, in solid form, a crude lithium salt containing the lithium salt and one or more reactive solvents coordinated or solvated with the lithium salt;
• contacting the crude lithium salt with at least one first anhydrous organic solvent under an inert condition so as to dissolve the crude lithium salt and thereby create a solution containing the lithium salt and the one or more reactive solvents, wherein,
• the solubility of the lithium salt in the at least one first anhydrous organic solvent is at least about 35% below 25° C.;
• and
• wherein the at least one first anhydrous organic solvent is a non-reactive solvent selected to replace at least a portion of molecules of the one or more reactive solvents bonded to ions from the crude lithium salt in the solution;
• subjecting the solution to a vacuum so as to remove the at least one first anhydrous organic solvent and at least a portion of the one or more reactive solvents to obtain a solid mass;
• treating the solid mass with at least one second anhydrous organic solvent in which the lithium salt is insoluble so as to remove at least a portion of any coordinated or solvated portion of the at least one first anhydrous organic solvent remaining in the solid mass after the subjecting of the solution to the vacuum to create a combination having an insoluble portion, and
• isolating the insoluble portion in an inert atmosphere:
• wherein the crude lithium salt contains one or more synthesis impurities that are remnants of a process used to synthesize the crude lithium salt, the method further comprising:
• a synthesis-impurity-reduction process that includes:
• contacting the crude lithium salt with at least one third anhydrous organic solvent under inert conditions so as to create a solution containing the lithium salt and the one or more synthesis impurities, wherein:
• solubility of the lithium salt in the at least one third anhydrous organic solvent is at least about 60% at room temperature;
• the solubility of each of the one or more synthesis impurities in the at least one third organic solvent is no more than about 20 parts per million (ppm) at room temperature;
• and
• the at least one third anhydrous organic solvent is provided to the solution in an amount in a range of about 50 wt. % to about 75 wt. % of the solution;
• adding at least one fourth anhydrous organic solvent to the solution to precipitate the one or more synthesis impurities as precipitated impurities, wherein:
• the lithium salt and each of the one or more synthesis impurities are substantially insoluble in the at least one fourth anhydrous organic solvent;
• and
• the at least one fourth anhydrous organic solvent is provided to the solution in an amount of less than about 10 wt. % of the solution;
• following the adding of at least one fourth organic solvent, isolating a filtrate from the precipitated impurities;
• and
• removing the one or more third anhydrous organic solvents and the one or more fourth anhydrous solvents present in the filtrate so as to create a solid mass of purified lithium salt.