Charge-discharge properties of hard carbon (HC) for sodium secondary batteries using NaFSA-C(1)C(3)pyrFSA (FSA: bis(fluorosulfonyl)amide, C(1)C(3)pyr: N-methyl-N-propylpyrrolidinium) ionic liquids were investigated. A Na/NaFSA-C(1)C(3)FSA/HC cell showed reversible capacity of 260 mAh (g-HC)(-1) at a constant rate of 50 mA (g-HC)(-1) at 363 K, maintaining cell capacities of approximately 95.5% of the initial capacity after 50 cycles. Coulombic efficiency was higher than 99.5% except for the initial few cycles, reaching 99.9% after 40 cycles. The Na/NaFSA-C(1)C(3)pyrFSA/HC cell also exhibited a high rate capability of 211 mAh (g-HC)(-1) at a rate of 1000 mA (g-HC)(-1), which corresponds to a charge rate of approximately 4C. (C) 2013 Elsevier B.V. All rights reserved.