Preparation And Properties Of Bis(Polyfluoroalkyloxysulfonyl)imide Derivatives

The fluorinated sulfonimide anion is a weakly coordinating anion. The charge on theanion could be effectively delocalized, due to the strong electron-withdrawing action ofthe fluorinated group and the conjugate action of the-SO₂-N-SO₂-group. As a result, theanion is rather resistant to anodic oxidation. The ionic liquids and alkali salts based on thefluorinated sulfonimide anion have satisfactory chemical and electrochemical performance.In the thesis, alkali salts and ionic liquids based two new fluorinated sulfonimide anions（i.e. bis （hexafluoroiso-propoxysulfonyl）imide anion （[（（CF₃）₂CHOSO₂）₂N], HFPSI）and bis（trifluoroe-thoxysulfonyl）imide anion （[CF₃CH2OSO₂）N], TFESI） weresynthesized, and the fundamental properties of them were investigated. The thesis mainlyincludes the following three parts：1. The part includes the preparation and characterization of ionic liquids based onHFPSI and TFESI anions.16ionic liquids were synthesized by the metathesis reaction.Their chemical structures were characterized by IR,¹H NMR and¹⁹F NMR. Theimportant physicochemical and electrochemical properties of these salts have beenmeasured, in terms of phase transition, viscosity, conductivity, thermal andelectrochemical stability. The ionic liquids based on HFPSI anion are all solid at roomtemperature, due to the large molecular weight of the anion. The melting points of themrang from41to96oC. Six of the ionic liquids based on TFESI anion are liquid at roomtemperature. EMI[TFESI] show the lowest viscosity （43.5cP at25oC） and the highestconductivity (1.82mS cm^-1at25oC), but the narrowest electrochemical window （4.6V）.The viscosities of the other five ionic liquids are above160cP, and the conductivities ofthem are below1mS cm^-1. But the electrochemical windows of them are nearly6V. Thedecomposition temperature of ionic liquids based on HFPSI and TFESI anions is above260oC.2. The part includes the preparation and thermal characterization of alkali salts basedon HFPSI and TFESI anions. Their chemical structures were characterized by IR,¹HNMR and¹⁹F NMR. The decomposition temperature of these alkali salts are above210oC. The alkali salts based on HFPSIanion have a slow decomposition process before themassive decomposition process.3. The part includes the properties of1M LiHFPSI-EC/EMC （3/7, v/v） electrolyte.The properties of the electrolyte were investigated by EIS, CV, LSV, chronoamperometryand so on. The LiHFPSI electrolyte exhibites relative low conductivity becasue of thelarge anion size, but the lithium ion transference number is up to0.7. Besides, theelectrolyte is rather resistant to anodic oxidation and is able to be passivated for the Alanode during the polarity process. Li/C and Li/LiCoO₂half cells investigation indicate thatLiHFPSI is compatible with the two ordinary electrodes of graphite and LiCoO₂.Meanwhile, the C/LiCoO₂Li-ion cells using LiHFPSI based electrolyte shows bettercycling properties and the less capacity loss than that of LiPF6based Li-ion cells.