Conjugated nanofibrous organic cathodes with high-density carbonyl/imine redox sites for superior NH4+/H+ co-storage

Abstract

NH₄⁺/H⁺ ions with small hydration sizes, light weight and rapid (de)coordination dynamics have emerged as promising charge carriers for advanced aqueous zinc-organic batteries (ZOBs). However, the limited-density redox sites and high redox barrier of NH₄⁺/H⁺ migration in organics pose significant challenges for advancing ZOBs. Herein, conjugated nanofibrous organic (CFO) cathodes with high-density carbonyl/imine redox sites are designed for superior non-metallic ion co-storage through π–π stacking interactions between benzene-1,3,5-tricarbaldehyde and 2,6-diaminoanthraquinone nanofibrous polymer molecular chains. The interconnected planar nanofibrous skeletons of CFO deliver consecutive electron delocalization pathways and ultralow reaction energy barriers that selectively couple with NH₄⁺/H⁺ ions (0.15 vs. 0.37 eV of Zn²⁺ ions), overcoming the sluggish reaction kinetics of rigid Zn²⁺. Consequently, the high-density carbonyl/imine redox sites coupled with high-kinetics NH₄⁺/H⁺ ions endow CFO cathodes with high capacity (385 mAh g⁻¹ at 1 A g⁻¹) and a high rate (212 mAh g⁻¹ at 100 A g⁻¹), while the robust conjugated network structures effectively suppress the dissolution of CFO cathodes to achieve a durable lifespan (50 000 cycles). This study highlights the importance of constructing conjugated organics with high-density redox sites to enhance effective non-metallic ion storage.