MXene-Boosted Imine Cathodes with Extended Conjugated Structure for Aqueous Zinc-Ion Batteries

Organic molecules have been considered promising energy-storage materials in aqueous zinc-ion batteries (ZIBs), but are plagued by poor conductivity and structural instability because of the short-range conjugated structure and low molecular weight. Herein, an imine-based tris(aza)pentacene (TAP) with extended conjugated effects along the C-N backbones is proposed, which is in situ injected into layered MXene to form a TAP/Ti₃C₂T_x cathode. Theoretical and electrochemical analyses reveal a selective H⁺/Zn²⁺ co-insertion/extraction mechanism in TAP, which is ascribed to the steric effect on the availability of active C-N sites. Moreover, Ti₃C₂T_x, as a conductive scaffold, favors fast Zn²⁺ diffusion to boost the electrode kinetics of TAP. Close electronic interactions between TAP and Ti₃C₂T_x preserve the structural integrity of TAP/Ti₃C₂T_x during the repeated charge/discharge. Accordingly, the TAP/Ti₃C₂T_x cathode delivers a high reversible capacity of 303 mAh g⁻¹ at 0.04 A g⁻¹ in aqueous ZIBs, which also realizes an ultralong lifetime over 10 000 cycles with a capacity retention of 81.6%. Furthermore, flexible Zn||TAP/Ti₃C₂T_x batteries with a quasi-solid-state electrolyte demonstrate potential application in wearable electronic devices. This work offers pivotal guidance to create highly stable organic electrodes for advanced ZIBs.