A High‐Rate and Long‐Life Aqueous Rechargeable Mg‐Ion Battery Based on an Organic Anode Integrating Diimide and Triazine

Aqueous Mg‐ion batteries (MIBs) lack reliable anode materials. This study concerns the design and synthesis of a new anode material – a π‐conjugate of 3D‐poly(3,4,9,10‐perylenetracarboxylic diimide‐1,3,5‐triazine‐2,4,6‐triamine) [3D‐P(PDI‐T)] – for aqueous MIBs. The increased aromatic structure inhibits solubility in aqueous electrolytes, enhancing its structural stability. The 3D‐P(PDI‐T) anode exhibits several notable characteristics, including an extremely high rate capacity of 358 mAh g−1 at 0.05 A g−1, A 3D‐P(PDI‐T)‖Mg2MnO4 full cell exhibits a reversible capacity of 148 mAh g−1 and a long cycle life of 5000 cycles at 0.5 A g−1. The charge storage mechanism reveals a synergistic interaction of Mg2+ and H+ cations with C−N/C=O groups. The assembled 3D‐P(PDI‐T)‖Mg2MnO4 full cell exhibits a capacity retention of around 95 % after 5000 cycles at 0.5 A g−1. This 3D‐P(PDI‐T) anode sustained its framework structure during the charge–discharge cycling of Mg‐ion batteries. The reported results provide a strong basis for a cutting‐edge molecular engineering technique to afford improved organic materials that facilitate efficient charge‐storage behavior of aqueous Mg‐ion batteries. An assembled 3D‐P(PDI‐T)‖Mg2MnO4 full cell exhibited capacity retention of around 95 % after 5000 cycles at 0.5 A g−1. The 3D‐P(PDI‐T) anode sustained its framework structure during charge–discharge cycles of Mg‐ion batteries. Results provide strong support for a cutting‐edge molecular engineering technique for improved organic materials that facilitate efficient charge‐storage behavior in aqueous Mg‐ion batteries.