Biredox-Ionic Anthraquinone-Coupled Ethylviologen Composite Enables Reversible Multielectron Redox Chemistry for Li-Organic Batteries.

Organic compounds bearing redox-active ionic pairs as electrode materials for high-performance rechargeable batteries have gained growing attention owing to the properties of synthetic tunability, high theoretical capacity, and low solubility. Herein, an innovative biredox-ionic composite, i.e., ethylviologen dianthraquinone-2-sulfonate (EV-AQ2 ), affording multiple and reversible active sites as a cathode material in lithium-organic batteries is reported. EV-AQ2 exhibits a high initial capacity of 199.2 mAh g-1 at 0.1 C rate, which corresponds to the transfer of two electrons from one redox couple EV2+ /EV0 and four electrons from two redox-active AQ- anions. It is notable that EV-AQ2 shows remarkably improved cyclability compared to the precursors. The capacity retention is 89% and the Coulombic efficiency approaches 100% over 120 cycles at 0.5 C rate. The results offer evidence that AQ- into the EV2+ scaffold with multiple redox sites are promising in developing high-energy-density organic rechargeable batteries.