Boosting redox electrochemistry of aromatic imide polymers by coupling with a sulfur-heterocyclic ring for advanced all-organic aqueous magnesium-ion batteries

Abstract

Easy dissolution and low redox activity are the main obstacles limiting the sustainability of organic electrode materials applied in aqueous magnesium-ion batteries (AMIBs). To conquer these issues, herein, we developed a novel aromatic polyimide-based organic polymer material (labeled as PTTDA) by coupling an aromatic imide with a thiadiazole-based sulfur heterocyclic ring for use as a promising electrode material in AMIBs. The constructed PTTDA molecule contains highly redox-reversible thioether linkages and imide bonds and features a long-range conjugated structure, which can synergistically enhance electrochemical activity and structural stability for reversible Mg²⁺ storage in a MgCl₂ aqueous solution. As a result, PTTDA employed as an active material for the AMIB anode delivers exceptional rate capability (107.7 mA h g⁻¹ at 20.0 A g⁻¹) and ultralong cycling stability (83.4% of capacity retention after 10 000 cycles). Besides, the all-organic full cell assembled with the PTTDA anode and the polyindole cathode achieves an outstanding power/energy density and long lifespan. This work provides a novel approach to the sustainable development of organic electrode materials and their potential application in aqueous metal-ion batteries.