Insoluble π –d -Conjugated Small Molecules Featuring p -Type Ligands Enable All-Organic Dual-Ion Batteries

Abstract Organic electrodes for secondary batteries are hindered by molecular dissolution and low operating voltages. Herein, we report a coordination-driven strategy to construct insoluble π–d conjugated small molecules (BTD-M, M = Cu, Ni, or Zn) featuring high-voltage p-type triphenylamine-derived ligands (N4′,N4′-diphenyl-[1,1′-biphenyl]-3,4,4′-triamine, BTD). By precisely tuning metal–ligand coordination, we thermodynamically lock discrete molecules against electrolyte dissolution while preserving unhindered access to active sites. The optimal BTD-Cu exhibits a narrow bandgap of 0.7 eV, enabling extensive electron delocalization for electronic conductivity. This electrode delivers a near-theoretical capacity of 134 mAh g–1 at 1C and still delivers 83 mAh g–1 at 10C. Leveraging bipolar redox chemistry of p-type ligands and metal centers, the symmetric all-organic dual-ion battery achieves an average voltage of 2.4 V and a cycle life exceeding 1000 cycles. This work establishes insoluble π–d conjugated small molecules as an accessible platform for organic battery design.