Synergistic Effects of F Doping and CNT Incorporation in ZnMn2O4 Cathode Materials to Achieve High-Performance Aqueous Zinc-Ion Batteries

Abstract

Mn-based materials are promising cathode candidates for aqueous Zn-ion batteries (AZIBs) because of their high-voltage platforms, environmental friendliness, and nontoxicity. However, their practical applications are limited by the rapid capacity decay caused by their slow electrochemical reaction kinetics and intrinsically poor conductivity. In this study, F-doped ZnMn₂O₄ (ZMO) (F-ZMO) microspheres incorporated with carbon nanotubes (CNTs) were synthesized and investigated to overcome these limitations. F-doping induced structural modifications by generating oxygen defects, which improved the ion diffusion and electronic conductivity. In addition, it improved the structure stability owing to the formation of strong metal-F bonds. These doping effects led to enhanced rate performance and cycle stability. Furthermore, the incorporation of CNTs complemented the insufficient electrical conductivity of the cathode material. The resulting F-ZMO/carbon nanotube (CNT) composites exhibited superior charge–transfer kinetics. Consequently, they achieved an enhanced discharge capacity of 122.2 mAh g⁻¹ at a high current density of 2.0 A g⁻¹, demonstrating significantly improved performance compared to those of ZMO and ZMO/CNT. These findings highlight the synergistic effect of F-doping and CNT incorporation in enhancing the electrochemical properties of ZMO cathodes and provide critical insights into the development of high-performance cathode materials for AZIBs.