Redox-enhanced ladder-type organic electrode enabling high-rate aqueous ammonium-ion batteries.

Redox-active organic compounds with tailored conjugated architectures have gained prominence as pivotal electrode materials in aqueous batteries, owing to their unique ion (de)intercalation mechanisms that avoid crystalline lattice distortion during redox processes. Despite their potential, organic materials are hindered by limitations including inadequate active site density and structural degradation due to electrolyte dissolution during electrochemical cycling. Addressing these limitations, we develop an innovative electron-delocalized organic molecule, designated as PTAQ, which incorporates a π-conjugated imidazole-linked framework with extensive electron delocalization and a reduced band gap, which is favorable for electron transfer. Additionally, a new redox active group (CN) was added, and the amount of CO was increased, thereby enhancing ion embedding capability, as validated by in-situ analyses and theoretical calculations. As electrode for aqueous ammonium-ion batteries (AAIBs), PTAQ exhibits a high specific capacity of 220.9 mAh g (at 1 A g) with wide operating voltage (-0.9-1.0 V) and maintains a capacity retention of 98.8 % after 10,000 cycles at 5 A g. Furthermore, an all-organic PTAQ//polyimide full cell was constructed, demonstrating a specific capacity of 65.6 mAh g at 1 A g over 200 cycles, with an impressive capacity retention rate of 94.2 %. This work advances the understanding of NH storage mechanisms in organic materials while establishing molecular engineering strategies for tailoring high-performance organic electrodes in aqueous ammonium-ion batteries (AAIBs). This enables technological innovation in sustainable energy storage systems with higher energy density.