Lithium bis(fluorosulfonyl)imide (LiFSI) has been studied as conducting salt for lithium-ion batteries, in terms of the physicochemical and electrochemical properties of the neat LiFSI salt and its nonaqueous liquid electrolytes. Our pure LiFSI salt shows a melting point at 145 degrees C, and is thermally stable up to 200 degrees C. It exhibits far superior stability towards hydrolysis than LiPF6. Among the various lithium salts studied at the concentration of 1.0 M (= mol dm(-3)) in a mixture of ethylene carbonate (EC)/ethyl methyl carbonate (EMC) (3:7, v/v), LiFSI shows the highest conductivity in the order of LiFSI > LiPF6 > Li[N(SO2CF3)(2)] (LiTFSI) > LiClO4 > LiBF4. The stability of Al in the high potential region (3.0-5.0V vs. Li+/Li) has been confirmed for high purity LiFSI-based electrolytes using cyclic voltammetry, SEM morphology, and chronoamperometry, whereas Al corrosion indeed occurs in the LiFSI-based electrolytes tainted with trace amounts of LiCl (50 ppm). With high purity, LiFSI outperforms LiPF6 in both Li/LiCoO2 and graphite/LiCoO2 cells. (C) 2010 Elsevier B.V. All rights reserved.