For sodium-ion battery, cathode properties of disodium rhodizonate, Na2C6O6, were investigated. Unlike other organic active materials, Na2C6O6 exhibited good rechargeable capacity about 270 mAh g(-1), corresponding to more than 2 Na insertion per molecule between 1.0 and 2.9 V with using 1 M NaClO4/PC as electrolyte. Na2C6O6 could also show the rechargeable capacity more than 90 mAh g(-1) even in acetylene black free pellets. The good cyclability was also confirmed in Na-ion cells with Na-predoped hard carbon anodes. (C) 2013 Elsevier Ltd. All rights reserved.