Asymmetric ammonium-based ionic liquids as electrolyte components for safer, high-energy, electrochemical storage devices

The synthesis of ionic liquids (ILs), based on the trimethyl-isobuty-ammonium cation, (N111i4)+, and, respectively, the bis(trifluoromethylsulfonyl)imide (TFSI), (fluorosulfonyl) (trifluoromethylsulfonyl)imide (FTFSI), and bis(fluorosulfonyl)imide (FSI) anions is herein reported. The NMR validation of the N111i4Br precursor as well as the ionic liquids is shown. The thermal properties were investigated via variable-temperature, coupled with mass spectroscopy, and isothermal thermo-gravimetrical analyses, and long-thermal tests. The TFSI-based IL exhibits a melting point of 29.93 °C, which is found to be shifted down to −0.12 and −14.32 °C for the FSI- and FTFSI-based samples, respectively. Additionally, the TFSI- and FTFSI-based samples are able to keep in super cooled state for more than one year. The investigated N111i4-based ionic liquids display an electrochemical stability window exceeding 5.5 V.