Electrochemical behaviors of polymer composit electrolytes containing imidazolium-type room-temperature molten salts

The effects of room-temperature molten salt addition on electrochemical properties of polymer com posite electrolytes (PCE) based on poly(ethylene oxide) (PEO) were studied. Alkyl-imidazolium salt, 1-butyl-3-methyl-imidazolium hexafluorophosphate (BMIPF ₆) could influence ion transference phenomena, resulting the change of ionic conductivity of PCE. The PCE containing 1.2 mole% BMIPF ₆ showed the slightly lower melting temperature than PEO-LiCI0 ₄. The PCE showed the highestion conductivity of 2.9*10 ^-4 S/cm, which is one-order-of-magnitude higher value than the pristine sample. This is probably originated from the improved ion transference and slightly decreased crys-tallinity. Li ion transference number was increased to 0.55 and the stable electrochemical voltage limit was upgraded to ̃4.3 V. Consequently, the ion conducting behaviors and the electrochemical stability had been improved by BMIPF ₆ addition.