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

Sodium 9,10-anthraquinone-2,6-disulfonate (Na2 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.