Surpassing the Redox Potential Limit of Organic Cathode Materials via Extended p-π Conjugation of Dioxin.

Abstract

The key to enabling high energy density of organic energy-storage systems is the development of high-voltage organic cathodes; however, the redox voltage (<4.0 V vs Li/Li⁺) of state-of-the-art organic electrode materials (OEMs) remains unsatisfactory. Herein, we propose a novel dibromotetraoxapentacene (DBTOP) redox center to surpass the redox potential limit of OEMs, achieving ultrahigh discharge plateaus of approximately 4.4 V (vs Li⁺/Li). As theoretically analyzed, electron delocalization between dioxin active centers and benzene rings as well as electron-withdrawing bromine atoms endows the molecule with a low occupied molecular orbital level by diluting the electron density of dioxin in the whole p-π conjugated skeleton, and the strong π-π interactions among the DBTOP molecules provide a faster electrochemical kinetic pathway. This tetraoxapentacene redox center makes the working voltage of OEMS closer to the high-voltage inorganic electrodes, and its chemical and structural tunability may stimulate the further development of high-voltage organic cathodes.