Cation Engineering Perovskite Cathodes for Fast and Stable Anion Redox Chemistry in Zinc-Iodine Batteries

Zinc-halogen batteries are promising for sustainable energy storage, offering high redox capacities at economical price points. However, they are hindered by issues such as the irreversibility caused by the dissolution of intermediates and the sluggish charge transfer, which limit their widespread adoption. Addressing these issues, bismuth-iodide perovskite cathodes are employed as a halogen element enriched model system. These perovskite cathodes demonstrate considerable anion redox capacities. In a combined simulation and experimental study, it is uncovered that the (BAD)BiI4 (BAD+ denotes benzamidinium) cathode, greatly improves interactions with iodine species and boosts charge transfer capability compared to its (BA)BiI4 (BA+ denotes benzylaminium) counterpart. These enhancements can be attributed to the synergistic effects arising from stronger Bi-I<middle dot><middle dot><middle dot>I halogen bonds and C & boxH;N & horbar;H<middle dot><middle dot><middle dot>I hydrogen bonds. The (BAD)BiI4 cathode attains a reversible I-/I0 redox chemistry with 92% capacity retention after 30 000 cycles at a current density of 10 A g-1I, outperforming previously reported anion redox batteries. Additionally, the defect-tolerant property and the I-/I0/I+ conversion of the (BAD)BiI4 are elucidated. The I5- forms a notably stronger bond with (BAD)BiI4 in comparison to I3-, which effectively mitigates polyiodide shuttling. These advantageous characteristics highlight the promise and adaptability of the developed perovskite cathodes for high-performance anion redox chemistry. This report on organic cation-engineered 1D bismuth-iodide perovskite cathodes for zinc-halogen batteries achieves remarkable capacity and high-rate cycling stability. A combined experimental and simulation study reveals the anion redox mechanism driving the electrochemical behavior. The advantageous electronic structure and chemical composition emphasize the potential and versatility of these newly designed high-performance perovskite cathodes. image