Conversion-Type Organic-Inorganic Tin-Based Perovskite Cathodes for Durable Aqueous Zinc-Iodine Batteries

摘要

Aqueous metal-iodine batteries have recently attracted widespread attention,but their intrinsic issues such as the undesired shuttle effect and volatility ofiodine hinder their reliable long-term performance. Herein, organic–inorganicMXDA_2SnI_6 (MXDA~(2+) denotes protonated m-xylylenediamine cation)perovskite microcrystals with a zero-dimensional arrangement of octahedralperovskite units offering high content of elemental iodine (46 wt% in thewhole cathode) are proposed as conversion-type cathode materials foraqueous Zn–I_2 batteries. Iodide anions deliver reliable electrochemical activityand are effectively immobilized on the cathode to relieve the shuttle processby both physical steric hindrance and chemical adsorption offered bylong-chain organic matrix and the presence of B-site Sn(Ⅱ) cations in theMXDA_2SnI_6 perovskite, respectively. Moreover, the formation of triiodideanions is alleviated in favor of a significant proportion of pentaiodide ionsduring the end of the charging process, enabled by increased formationenergy of I_3? and effective confinement via Sn–I…I halogen bonds andN–H…I hydrogen bonds, as revealed by density functional theory calculations.As a result, rechargeable aqueous Zn–I_2 batteries are realized that achieve achampion capacity of over 206 mAh g~（?1）I at 0.5 A g~（?1） (close to the theoreticallimit), and outstanding rate capability with a capacity retention of 87% at 3 Ag?1. Suppressed shuttle of polyiodide anions endows aqueous Zn–I_2 batterieswith prolonged cyclic stability, namely high capacity retention of 95% after5700 cycles at 1 A g~（?1）. This study promotes the development ofhigh-performance cathode materials for metal-I2 batteries by revealing thefeasibility of using ionic perovskites as conversion-type cathodes.