Long-lifespan Polyanionic Organic Cathodes for Highly Efficient Organic Sodium-ion Batteries

An organic Na-ion battery is reported with a polyanionic 9,10-anthraquinone-2,6-disulfonate (Na₂ AQ26DS, 130 mAh g^-1 ) cathode and the Na-intercalated state (Na₄ TP) of sodium terephthalate (Na₂ TP, 255 mAh g^-1 ) as the anode. The resulting full cells deliver the maximum discharge capacity of 131 mAh g^-1 _cathode in 0.5-3.2 V, simultaneously maintaining the average value of ≈62 mAh g^-1 _cathode during 1200 cycles (0.5 A g^-1 , ≈4 C). These results are among the best performing organic sodium-ion full cells reported to date.