High-performance Zn-I₂ batteries enabled by porous hetero-carbon nanofiber hosts with TiO₂ homojunctions

Abstract

Zinc–iodine (Zn–I2) batteries have emerged as promising candidates for next-generation energy storage systems due to their high theoretical energy density, cost-effectiveness, and enhanced safety. However, critical challenges such as polyiodide shuttle effects and sluggish redox kinetics at the cathode–electrolyte interface impede their practical implementation. In this study, we design a hierarchically porous hetero-carbon nanofiber-based iodine host material, incorporating TiO2 active sites with homojunction configurations, designed to simultaneously immobilize and catalytically convert polyiodide species. Through integrated density functional theory calculations and comprehensive experimental characterization, we reveal that the synergistic hetero-/homojunction structure substantially improves charge transfer efficiency and catalytic activity, effectively mitigating polyiodide diffusion while promoting redox kinetics. The optimized band structure endows the cathode with a high specific capacity of 190.5 mAh·g−1 and exceptional cycling stability, retaining 98.9% of its capacity after 50,000 cycles under high iodine loading (8 mg·cm−2). Furthermore, the structural flexibility of this cathode enables the development of high-performance flexible Zn–I2 batteries, opening new avenues for wearable energy storage devices.