Bridged-Ring Structure Facilitating Ultrahigh Utilization of Active Sites in Organic Molecules for High-Performance Aqueous Batteries

Abstract

Organic electrode materials have attracted extensive attention for their tunable properties, diverse structure, and environmental sustainability. However, the actual reported capacities are often significantly lower than the theoretical capacities. Here, 6-cyano-substituted triptycene-fused quinacrizine (6CNTFQ) is synthesized, an organic imine molecule characterized by a bridged-ring structure and extensive 3D π-conjugated plane, as the negative electrode for aqueous batteries. 6CNTFQ exhibits an impressive capacity of 398 mAh g⁻¹ at 0.1 A g⁻¹ (0.25 C), demonstrating 88% of the theoretical capacity, and exhibits exceptional capacity stability over 10 000 cycles. The exceptional performance is a result of the presence of multiple accessible active sites, the conjugated planes within a 3D framework, and the robust bridged ring structure. During the discharge process, K⁺ preferentially binds to C≡N sites to form 6CNTFQ-K, subsequently binding to the C═N site to produce 6CNTFQ-12K. Ni(OH)₂//6CNTFQ cells attain a maximum capacity of 190 mAh g⁻¹ at 1 A g⁻¹, demonstrating exceptional rate performance, remarkable cycle stability exceeding 10 000 cycles, and an energy density of 162 Wh kg⁻¹. This work sheds light on the organic electrode materials featuring a 3D bridged-ring structure and extended conjugated planes for aqueous batteries.