Electrophilic N, P co-doped carbon enabling highly reversible iodine redox chemistry for ultra-stable bismuth-based zinc-ion batteries

Abstract

The pursuit of high-performance cathode materials is paramount for the deployment of aqueous zinc-ion batteries (ZIBs) in large-scale energy storage. Despite their high theoretical capacity and cost-effectiveness, bismuth (Bi)-based electrodes are often hampered by inferior cycling stability and sluggish redox kinetics. Herein, we report a composite cathode structure consisting of bismuth nanoparticles encapsulated within an N, P co-doped carbon framework (Bi@NPC), complemented by an iodide-based redox electrolyte additive to synergistically boost electrochemical performance. The integration of I⁻ ions activates a highly reversible I⁰/I⁻ redox couple, which provides additional capacity and accelerates charge transfer. Density functional theory (DFT) calculations elucidate that the N, P co-doped carbon matrix offers enriched electrophilic active sites, which not only catalyze the transformation of iodine species but also effectively mitigate the “shuttle effect” of polyiodide intermediates. Consequently, the Bi@NPC electrode delivers a superior specific capacity of 399.3 mAh g⁻¹ at 1.0 A g⁻¹ and demonstrates exceptional long-term durability, maintaining 95.4% capacity retention after 10 000 cycles at 5.0 A g⁻¹. As a proof of concept, a flexible 3D interdigital Zn//Bi@NPC battery was assembled to power a Bi@NPC-based photodetector, highlighting its practical viability. This study provides a robust strategy for engineering high-capacity and ultra-stable bismuth-based energy storage systems.