(Keynote) Ionic Liquids, Mixed Electrolytes and Their Iongels for Stable Na Metal Devices

Sodium batteries are being intensively studied as an alternative for existing Li-ion and more traditional Pb-acid technologies, in particular for stationary energy applications and as safer and cheaper longer term alternatives. As with Li battery technologies, there is intense activity in developing new electrode materials to increase the capacity and energy density of these emerging devices. Electrolyte advances are also critical for improving the safety and performance, enabling high energy density and higher voltage electrodes. We have been developing ionic liquid based electrolytes which enable stable Na metal cycling and demonstrate enhanced cycling stability with a number of cathode materials including NFP, layered oxides, air electrodes as well as supercapacitor carbon based electrodes in ‘hybrid’ devices.[1-5] Surprisingly, we have also recently found that the addition of small quantities of water has been shown to improve the electrochemical performance. Iongels based on a combination of the ionic liquid and various polymers have also been investigated as solid state electrolytes for all solid state batteries. This talk cover our recent work in understanding the structure, transport and electrochemical behaviour of these novel sodium electrolytes and show progress in their application in sodium devices.