NaFSA-C1C3pyrFSA ionic liquids for sodium secondary battery operating over a wide temperature range

The physicochemical properties of NaFSA-C(1)C(3)pyrFSA ionic liquids were investigated to explore their potential as new electrolytes for sodium secondary batteries operating over a wide temperature range. The viscosity and ionic conductivity of NaFSA-C(1)C(3)pyrFSA with a molar ratio of 2:8 were 16.7 cP and 15.6 mS cm(-1), respectively, at 353 K. The electrochemical window of this ionic liquid was 5.2 V at 353 K with sodium metal deposition determining the cathode limit. A Na/NaFSA-C(1)C(3)pyrFSA/NaCrO2 cell exhibited stable charge-discharge behaviour at 298 and 353 K. The discharge capacities of 92 and 106 mAh (g-NaCrO2)(-1) were observed at 298 and 353 K, respectively, at 20 mA g(-1). The Coulombic efficiency was higher than 99% during the charge-discharge tests except for the initial few cycles. The cell also showed high discharge rates, reaching 500 mA g(-1) at 353 K. (C) 2013 Elsevier B.V. All rights reserved.