Realizing that organic carbonates might not be the optimum solvents for lithium bis(oxalato)borate (LiBOB), efforts were made to tailor a "dedicated" electrolyte composition for this new salt. It was discovered that lactone-based cosolvents can effectively dissolve LiBOB up to high concentrations, and the electrolytes thus formulated generate high ionic conductivity as well as low interfacial resistance on graphitic electrode. However, lactones tend to increase the irreversible capacity associated with the 1.70 V reduction process of bis(oxalato)borate (BOB) anion on carbonaceous anode surface, while performances of the lithium-ion cells at elevated temperatures deteriorate with the lactone content. Thus, compromises have to be made by using linear carbonates to suppress the irreversible capacity in the formation cycles and ethylene carbonate to improve the thermal stability of the interfacial films formed. A preliminary study of LiBOB anodic stability on various cathode surfaces seems to indicate that the oxidative decomposition of BOB anion is catalyzed by Co-rich surfaces. (C) 2008 The Electrochemical Society.