Highly Stable and High Rate‐Performance Na‐Ion Batteries Using Polyanionic Anthraquinone as the Organic Cathode

Sodium 9,10‐anthraquinone‐2,6‐disulfonate (Na 2 AQ26DS), with polyanionic character and two O−Na ionic bonds, is found to be a highly stable organic cathode in Na‐ion batteries, delivering capacities of approximately 120 mAh g −1 for 300 cycles (50 mA g −1 ) and around 99 mAh g −1 for 1000 cycles (1 A g −1 ). These results are the best performance reported to date for small‐molecule, anthraquinone‐based organic cathodes in Li‐, Na‐, or K‐ion batteries.