Different performance of metal-N-C catalyst in dual-electron and multi-electron zinc-iodide battery systems

With high energy density, low cost, and environmental friendliness, aqueous zinc-iodide batteries (AZIBs) have garnered considerable attention. However, iodine and iodides exhibit poor redox kinetics and low conductivity. Meanwhile, the shuttle effect of intermediate polyiodides formed during cycling limits the application of AZIBs. In this study, we design and develop several metal single-atom-based metal-N-C catalysts from designed zeolitic imidazolate framework (ZIF) precursors. By optimizing both the ZIF pore structure and screening metal elements, we find that accordion-structured metal-N-C with bimodal porosity is most suitable for I₂ loading and mass transfer. Among all these metal-N-C, the Cu-N-C/I₂ exhibits the highest capacity in both dual-electron and multi-electron systems. In the multi-electron system, however, most metal-N-C catalysts are not stable during cycling, especially at large current densities, except Ni-N-C. The Ni-N-C/I₂ cathode achieves a high specific capacity of 535.9 mAh g⁻¹ after 500 cycles at 1 A g⁻¹, a specific capacity of 230.8 mAh g⁻¹ at 5 A g⁻¹, and long-cycle performance exceeding 6000 cycles.