The properties of the Li/LiCoO2 cell containing several RTILs with three different anions were investigated. Introducing the asymmetric nature to anionic species using amide improved the viscosity and conductivity of the RTIL, however, the rate properties of the cell was not enhanced very much. Declined cathodic stability seems to be responsible for the result. In the case of the stable system consisting of quaternary ammonium cation and imide anion, both of cycling properties and Coulombic efficiency during the cycling were satisfactory and the viscosity dominated the rate properties of the cell. The performance of the Li/LiCoO2 cell in this study was almost consistent with the stability of Li-electrolyte interface evaluated by ac impedance measurement. (c) 2005 Elsevier B.V. All rights reserved.