Electrospinning Machine| Conjugated Nanofibrous Organic Cathodes with High-Density Carbonyl/Imine Redox-Sites for Superior NH4+/H+ Co-Storage

NH4+/H+ is considered an ideal charge carrier for novel aqueous zinc-organic batteries due to its small hydrated size, light mass, and fast reaction kinetics. However, matching cathode materials must be designed to fully unlock its potential. Carbonyl/imine-based small molecules have attracted attention for their superior redox activity and cation coordination sensitivity but face challenges such as insufficient utilization of active sites, low electronic conductivity, and solubility in electrolytes, leading to electrode capacity decay and reduced cycle life.

Professor Liu Mingxian and Professor Gan Lihua’s team at Tongji University has long been dedicated to research on high-efficiency energy storage materials for application in new energy battery development. Recently, the group designed a high-density carbonyl/imine conjugated nanofiber cathode material. The fully exposed active sites and robust conjugated planar network structure provide ultra-low reaction energy barriers and continuous electron delocalization pathways, achieving exceptional NH4+/H+ co-storage. The findings were published in Materials Horizons under the title "Conjugated Nanofibrous Organic Cathodes with High-Density Carbonyl/Imine Redox-Sites for Superior NH4+/H+ Co-Storage."

Experimental characterization and theoretical calculations reveal that benzene-1,3,5-tricarboxaldehyde and 2,6-diaminoanthraquinone, with complementary electronic properties, form a conjugated nanofiber polymer through π-π planar stacking. This polymer exhibits high-density carbonyl/imine active sites, low bandgap, and strong dissolution resistance, facilitating faster electron transfer kinetics and electrode redox rates.

Electrochemical studies show that the conjugated nanofiber polymer, when used as a cathode material in aqueous zinc-organic batteries, delivers high specific capacity (385 mAh g−1@1 A g−1), excellent rate performance (212 mAh g−1@100 A g−1), and outstanding cycle life (86.3% capacity retention after 50,000 charge-discharge cycles).

Ex situ spectroscopic studies confirm that the robust conjugated planar network structure effectively suppresses the dissolution of active functional groups, fully exposes carbonyl/imine electroactive centers, and triggers highly reversible redox reactions.

Molecular dynamics simulations demonstrate that, owing to low activation energy (0.15 vs. 0.37 eV), carbonyl/imine active sites preferentially coordinate with high-kinetics NH4+/H+ via a two-step five-electron redox reaction, overcoming the sluggish interfacial charge transfer caused by Zn2+’s high desolvation energy barrier, enabling stable and rapid energy storage.

Theoretical calculations verify strong interactions between carbonyl/imine sites and NH4+/H+ in the conjugated nanofiber polymer, forming stable non-metallic ligand configurations and significantly enhancing NH4+/H+ storage capacity.This work expands the design strategy of high-density active-site conjugated organic materials to improve non-metal ion storage performance, advancing the development of advanced zinc-organic batteries.

Paper link: https://doi.org/10.1039/D5MH00859J