Synthesis And Characterization Of Lithium Salts Containing Super-delocalized Sulfonimides Anion

In recent years,Lithium salts with fluorinated sulfonylimide anion have received increasing attention due to their good stability and electrochemical properties.And Lithium salts with super-delocalized sulfonylimide anion show a series of superior properties such as strong oxidation resistance,good thermal stability,high solubility and weak coordination because of its larger volume,more delocalized structure,and more flexible group backbone(-SO2-N-S(O)=N-SO2-).This makes its use as a conductive lithium salt in lithium battery electrolyte may have more excellent physicochemical and electrochemical properties,so the study of this type of lithium salt is of great significance.The main work of this article is: 1.Synthesis of lithium(S-(trifluoromethyl)-N-((trifluoromethyl)sulfonyl)sulfonimidoyl)((trifluoromethyl)su-lfonyl)imide(Li[(CF3SO2))(CF3SO2)-N=S(=O)(CF3))N];Li[s TFSI])and lithium(S-(trifluoromethyl)-N-((trifluoromethyl)sulfonyl)sulfonimidoyl)((perfluorobutyl)sulfonyl)sulfonyl)imide(Li[(CF3SO2)(CF3SO2-N=S(=O)(C4F9))N];Li[s TNFSI])and four other alkali metal salts containing [s TNFSI]-(Na[s TNFSI],K[s TNFSI],Rb[s TNFSI],and Cs[s TNFSI]).The structures of two types of potassium salts containing different anions were characterized by 19 F NMR and ESI-MS.And the phase transition behaviors of five alkali metal salts containing [s TNFSI]-and four kinds of lithium salts(Li TFSI,Li TNFSI,Li[s TFSI] and Li[s TNFSI])were comparatively studied.2.The electrolytes 3 mol L-1 Li X-1,3-dioxolane(DOL)/dimethoxyethane(DME)(1:1,v/v)(X=[s TFSI],TFSI)were prepared.And then we demonstrated a coparetive study of their physicochemical and electrochemical properties.In addition,the compatibility with metallic lithium interface was investigated by cycling of Li/Li cell.The results show that both types of super-delocalized anions can effectively reduce the lattice energy of their corresponding metal salts.This is of great significance for optimizing the anion structure to obtain the molten salt electrolyte.Moreover,the electrolyte formulated with Li[s TFSI],which has a larger volume and a more delocalized anion,has higher conductivity,higher lithium-ion transference number,and better anodic stability.In the Li/Li cell,the polarization voltage changes regularly within 400 h,which fully shows that that the interface formed by Li[s TFSI] electrolyte and metallic lithium has good stability.