Achieving Ultra‐High Proton‐Storage in a Nitro‐Substituted Organic Molecule via Nucleophilic Functionalization

Abstract The urgent need for sustainable energy storage has spurred interest in aqueous proton batteries (APBs) utilizing the “Grotthuss mechanism” for proton conduction. However, the development of APB devices is hindered by the lack of efficient proton‐storage electrodes. Organic materials, with tunable structures and eco‐friendly synthesis, show promise but face challenges related to limited redox‐active sites and suboptimal electronic properties. Here, a nitro‐substituted organic molecule is introduced via nucleophilic functionalization, hexazineazatriphenylene trinitro (HATNTN), which is able to facilitate a 12‐electron proton‐coupled redox‐active mechanism and optimize its electronic properties through lowered LUMO levels, reduced local ionization energy, and augmented electrophilic reactivity toward protonation. The HATNTN electrode manifests a proton‐storage capacity of 349.3 mAh g −1 at 1 A g −1 (1.6 C) and upholds 124 mAh g −1 even at 100 A g −1 (160 C), marking record‐high capacity for proton‐storage organic entities. A full‐cell APB with HATNTN anode and MnO 2 cathode delivers a substantial anode capacity of 253 mAh g −1 , a high full‐cell energy density of 159.2 Wh kg −1 , and an ultralong stability over 11500 cycles. The device showcases exceptional safety without thermal runaway and a low self‐discharge rate of 4.58% per day, significantly enhancing the potential of organic anode materials for high‐performance proton storage.