Inhibition of shuttle effect in organic cathode and in situ mechanistic exploration

Abstract

Organic p-type cathode materials are promising for sustainable energy storage due to their abundance, environmental compatibility, and high operating voltages exceeding 3.5 V. However, their application is constrained by high solubility in electrolytes, leading to shuttle effect and inferior cycle stability. Herein, we introduced 9,9-dimethylacridine (DMAC) as a novel redox-active moiety in cathode material design. The small polar -C(CH3)2 group in DMAC stabilizes its oxidized form (DMAC +• ), restricting shuttle effect in polar electrolytes and achieving excellent cycling stability (76% capacity retention after 3000 cycles). Moreover, trace amounts of dissolved DMAC +• serve as redox mediators, enhancing conductivity and enabling a high active material ratio (73 mAh g -1 @90 wt%). Importantly, the integration of aggregation-induced emission (AIE) properties enables in situ fluorescence imaging, realizing visualization of the dissolution/ reprecipitation processes and providing insights into the shuttle effect. Coupled with electrochemical quartz crystal microbalance with dissipation (EQCM-D) analysis, this study advances DMAC-based cathodes and establishes a framework broadly applicable to other anion storage systems where DMAC redox-active centers contact with polar electrolytes.