Insight into Robust Anion Coordination Behavior of Organic Cathode with Dual Elongated π-Conjugated Motifs

Organic electrode materials offer multi-electron reactivity, flexible structures, and redox reversibility, but encounter poor conductivity and durability in electrolytes. To overcome above barriers, we propose a dual elongation strategy of π-conjugated motifs with active sites, involving the extended carbazole and electropolymerized polymer, which enhances electronic conductivity by the electronic delocalization of electron-withdrawing conjugated groups, boosts theoretical capacity by increasing redox-active site density, and endows robust electrochemical stability attributed to the nanonetwork feature of polymer structures. As a proof-of-concept, 5,11-dihydridoindolo[3,2-b]carbazole (DHIC) is selected as the model cathode material for a dual-ion battery, with elongated carbazole groups functioning both as redox-active centers and polymerization anchors. Electrochemical comparisons and theoretical simulations validate the excellent specific capacity, accelerated reaction kinetics, and enhanced anion storage stability imparted by the dual elongated π-conjugated system containing both carbazole motif and electropolymerized DHIC (pDHIC). Simultaneously, the coordination interaction between pDHIC and anions is innovatively evidenced through operando electron paramagnetic resonance spectra. As anticipated, pDHIC cathode delivers an unprecedentedly high specific capacity of 197 mAh/g at 50 mA/g, far outperforming graphite cathodes, and maintains excellent cycling stability with a capacity retention of 86.1 % over 500 cycles. This synergetic strategy sheds light on the performance revolution of organic electrode materials.