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

With the increasing need for reliable storage systems, the conversion-type chemistry typified by bromine cathodes has attracted 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, we proposed a novel low-dimensional halide hybrid perovskite cathode, TmdpPb 2 [IBr] 6 , which served 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. As such, the Zn||TmdpPb 2 [IBr] 6 battery delivered 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 retention 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 around 99%. The work highlighted the promising conversion-type cathodes based on metal-halide perovskite materials. This article is protected by copyright. All rights reserved.