The synergistic effect of triazine-N and secondary amine-N anchors iodine species with MXene composite cathode for stable aqueous Zn–I₂ battery

Aqueous Zn–I₂ battery (AZIBs) has attracted wide attention with its low cost, high capacity, low reduction potential and high safety. Iodine-based materials have the advantages of environmental protection, excellent cycle stability and low cost. However, there are some challenges, such as poor conductivity, slow kinetics and solubility of iodine species. Therefore, an innovative approach is proposed that exhibits excellent electrical conductivity and effectively anchors iodine species through physical trap with microporous structure and strong chemical adsorption with the synergistic effects of triazine and secondary amine-N. The dynamic transfer mechanism between them enhances catalytic conversion of iodine. The melamine-formaldehyde polymer and MXenes (Ti₃C₂T_x) composite (NC@TC) is prepared as host material of iodine by the electrostatic self-assembly. DFT calculation indicates thermodynamically favorable adsorption of iodine species, significantly accelerating the iodine redox reaction kinetics. Specifically, it reaches a discharge capacity of 183.07 mAh g⁻¹ at 1.0C ever after 200 cycles (1.0C = 211 mAh g⁻¹). Moreover, it also has excellent cycling performance, maintaining 81.33 % capacity after 5000 cycles. Additionally, NC@TC cathodes maintain good electrochemical performance under high current conditions and pouch cell structures. This work highlights the potential of MXene-based composites as promising iodine host materials for advanced Zn–I₂ batteries.