Conjugated Enhanced Polyimide Enables High‐Capacity Ammonium Ion Storage

Abstract Aqueous ammonium ion batteries (AIBs) have emerged as a promising next‐generation rechargeable battery due to their safety, sustainability, abundant resources, and superior electrochemical performance. However, organic anode materials, particularly polyimide anode materials, suffer from low specific capacity caused by limited active sites. Herein, the study has developed a micro‐granular‐structured π‐conjugated enhanced polyimide (PTPD) as the anode material for AIBs. The large π‐conjugated enhanced structure enables long‐range electron delocalization, decreased bandgap, and reduced spatial steric hindrance, resulting in increased active sites capable of storing NH 4 + ions. PTPD exhibits reversible oxidation and reduction reaction in (NH 4 ) 2 SO 4 solution, delivering a high specific capacity of 206.67 mAh g −1 at a current density of 0.5 A g −1 , exceptional rate capability, and excellent cycling stability with a capacity retention of 74.28% after 2500 cycles at a current density of 10 A g −1 . Furthermore, theoretical simulations and materials analysis demonstrate that PTPD undergoes enol‐keto transformation of carbonyl groups, effectively capturing NH 4 + to store charges. This study provides an effective strategy for designing polymer‐based AIBs anodes with high specific capacity and cycling stability.