Ionic Liquid Electrolytes for Alkali Metal Electrochemical Devices: Low Melting Chloroaluminate Binary Solutions and the Alkali Trapping Problem

With an interest in developing low temperature versions of electrochemical energy storage and generation systems, like the ZEBRA (chloroaluminate electrolyte) cell, we have repeated and extended earlier studies of sodium chloroaluminate electrolytes whose liquidus temperatures have been lowered by mixing with chloroaluminates of weak-­‐field, low-­‐melting, chloroaluminate ionic liquids. We consider both organic and inorganic cations of low charge intensity, and here report on the case of dialkylimidazolium cations. The non-­‐additive effects seen in conductivity, due to asymmetric cation-­‐anion interactions and alkali cation trapping, are quantified and discussed in terms of cation competition models. Finally, the importance of these effects in controlling the kinetics of cell performance (to be reported separately) is assessed.