(60aj) An Ionic Liquid Based Low-Temperature Electrolyte System for Molecular Electronic Transducer Sensing (MET) Applications

Ionic liquids (ILs) possess remarkable properties as a promising class of liquid electrolytes for electrochemical devices. In particular, the wide liquidus temperature window of IL-based electrolytes enables the devices to operate at extreme temperatures and extends their applications to harsh environmental conditions where the conventional aqueous- or organic-based electrolytes may easily fall short. Despite the popularity of high-temperature applications, the progress of employing IL-based electrolytes to support devices at low temperatures is limited mainly due to the loss of the ion mobility as temperature decreases. Although adding a low-viscosity solvent to ILs could boost the transport of ions to enhance the ionic conductivity, the occurrence of potential phase transitions, such as crystallization and glass transition, still hinders their application as low-temperature electrolytes. In order to overcome such a challenge, we present an approach that utilizes a binary mixture system of 1-butyl-3-methylimidazolium iodide ([BMIM][I]) and butyronitrile (BCN) to design a low-temperature electrolyte for molecular electronic transducer (MET) applications. The reported electrolyte system exhibits an extremely low glass transition temperature down to –150 °C without any observation of recrystallization, which shows a strong potential to support MET sensing technology that relies on induced motions of the liquid electrolyte. Other key characteristics of the electrolyte system, including viscosity, ionic conductivity, and electrochemical stability, were studied experimentally to provide assessment for the targeted MET sensing operation. The effect of molecular interactions between ions in the mixture were also investigated by spectroscopy analysis (FTIR and Raman) and complemented by molecular dynamics (MD) simulations, disclosing a possible explanation for evolutions of macroscopic bulk solution properties from a molecular level. The results from this work provide a promising liquid electrolyte system that not only extends the employment of MET sensing technology to space explorations but also allows other I^-/I₃^- redox couple based electrochemical applications to operate at low temperatures.