Molecular Engineering of π-Conjugated C═O/C═N Cathode for Ultrastable Organic Zinc-Ion Batteries.

Organic materials with high capacity and sustainability are widely used in aqueous zinc-ion batteries (ZIBs), yet organic materials with multi-redox centers and stable structures are seldom reported. Herein, we design a novel π-conjugated organic molecule with twelve C═O and C═N active sites, BDQDT (Bisdipyrido[4,3-a:3',4'-c]quinoxaline[3,2-a:2',3'-h]-11,24-dihydrophenazine-10,12,23,25-tetraone), enabling strong electron delocalization, reinforced π-π stacking, and suppressed dissolution. As a result, BDQDT ZIBs exhibit excellent rate capability with 84.0 mAh g-1 at 20 A g-1 and outstanding cycling stability after 12 000 cycles. Besides, In situ characterizations combined with DFT calculations confirm Zn2+/H+ co-insertion mechanism. The optimized discharged structure is identified as BDQDT-1Zn-10H, binding from one BDQDT molecule with one zinc ion and ten protons. Impressively, flexible Zn-ion device of BDQDT maintains stable properties under various mechanical deformations, and could power a humidity sensor. Prospectively, this work would build molecular engineering strategies for high-capacity and stable organic ZIBs.