Halide Exchange in Perovskites Enables Bromine/Iodine Hybrid Cathodes for Highly Durable Zinc Ion Batteries

Abstract With the increasing need for reliable storage systems, the conversion‐type chemistry typified by bromine cathodes attracts considerable attention due to sizeable theoretical capacity, cost efficiency, and high redox potential. However, the severe loss of active species during operation remains a problem, leading researchers to resort to concentrated halide‐containing electrolytes. Here, profiting from the intrinsic halide exchange in perovskite lattices, a novel low‐dimensional halide hybrid perovskite cathode, TmdpPb 2 IBr 6 , which serves not only as a halogen reservoir for reversible three‐electron conversions but also as an effective halogen absorbent by surface Pb dangling bonds, C─H…Br hydrogen bonds, and Pb─I…Br halogen bonds, is proposed. As such, the Zn||TmdpPb 2 IBr 6 battery delivers three remarkable discharge voltage plateaus at 1.21 V (I 0 /I − ), 1.47 V (I + /I 0 ), and 1.74 V (Br 0 /Br − ) in a typical halide‐free electrolyte; meanwhile, realizing a high capacity of over 336 mAh g −1 at 0.4 A g −1 and high capacity retentions of 88% and 92% after 1000 cycles at 1.2 A g −1 and 4000 cycles at 3.2 A g −1 , respectively, accompanied by a high coulombic efficiency of ≈99%. The work highlights the promising conversion‐type cathodes based on metal–halide perovskite materials.