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

Easy dissolution and low redox-activity are the main obstacles to limit 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 thiophene-based sulfur heterocyclic ring for using as a promising electrode material in AMIBs. The constructed PTTDA molecule contains highly redox-reversibile thioether linkages and imide bonds and features 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, the PTTDA employed as active material for 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.