One ether-functionalized guanidinium ionic liquid is used as new electrolytes for lithium battery. Viscosity, conductivity, behavior of lithium redox, chemical stability against lithium metal, and charge–discharge characteristics of lithium batteries, are investigated for the IL electrolytes with different concentrations of lithium salt. Though the cathodic limiting potential of the IL are 0.7V vs. Li/Li+, the lithium plating and striping on Ni electrode can be observed in the IL electrolytes, and the IL electrolytes show good chemical stability against lithium metal. Li/LiCoO2 cells using the IL electrolytes without additives have good capacity and cycle property at the current rate of 0.2C when the LiTFSI concentration is higher than 0.3molkg−1, and the cell using the IL electrolyte with 0.75molkg−1 LiTFSI owns good rate property. The activation energies of the LiCoO2 electrode for lithium intercalation are estimated, and help to analyze the factors determining the rate property.