Diffusion coefficients, spin-lattice relaxation times, and chemical shift variations of NMR spectra in LiTFSI-doped ether- and allyl-functionalized dicationic ionic liquids

An ether- and allyl-functionalized dicationic ionic liquid ([AIOIA][TFSI]) is prepared and the effects of the addition of lithium bis(trifluoromethanesulfonyl)imide into [AIOIA][TFSI] on hydrogen, fluorine, and lithium diffusion coefficients, spin-lattice relaxation times, and chemical shift of one-dimensional (1D) nuclear magnetic resonance (NMR) spectroscopy are studied. NMR longitudinal relaxation relation time measurements (400 MHz) show that the 1H-T 1 and 19F-T 1 values of neat [AIOIA][TFSI] and LiTFSI-doped [AIOIA][TFSI] increase with increasing temperature and decrease with increasing LiTFSI concentration. The chemical shift variations in 1D NMR spectroscopy show an upfield shift in 1H and 19F spectra with increasing lithium salt concentration in LiTFSI-doped [AIOIA][TFSI]. A tendency of cluster-like structural formation is the dominant effect when LiTFSI is added to [AIOIA][TFSI]. The Li ion transference number increases with increasing temperature and increasing LiTFSI mole fraction in LiTFSI-doped [AIOIA][TFSI]. The high t Li with high lithium salt concentration can compensate for the slower lithium transport caused by high viscosity.