Efficient synthesis of LiFSI based on Reaction-Extraction coupling method

Lithium bis(fluorosulfonyl)imide (LiFSI) is a promising electrolyte for lithium-ion batteries. However, the lithiation reaction during the LiFSI synthesis process is accompanied by a LiFSI hydrolysis reaction, which negatively affects the LiFSI yield and poses potential safety risks. In this study, we delve into the reaction equilibrium and hydrolysis behavior during the lithiation reaction and identify that the high temperature and strong alkali used in the reactive distillation process are the key factors leading to LiFSI hydrolysis. As a solution, a novel method for effectively synthesizing LiFSI using reaction-extraction coupling method is proposed and rigorously tested for various factors, including temperature, alkali equivalent, type of solvent, and dosage. The research culminated in developing a multistage continuous membrane extraction process, which achieves a remarkable conversion of over 99.7% and minimizes LiFSI hydrolysis to less than 0.05%.