Polymerized Melamine Catalyzes Direct I <sup>−</sup> /I <sub>2</sub> Conversion via ─N═N─ Motif for HighCapacity Zn‐I <sub>2</sub> Batteries
Yueyang Wang, Yanan Lv, Shiqiang Wei, Linfeng Yu, Bichen Yuan, Tofik Ahmed Shifa, Mudasir Muhammad, Runze Wang, Jiazhan Li, Yi Zhao, Xiaoming Sun
Abstract
Abstract To fundamentally solve low iodine conversion efficiency and severe polyiodide shuttling, a high‐performance catalytic organic cathode is developed by in situ polymerizing melamine (MA) on activated carbon (denoted as pMA@AC) for high‐capacity Zn‐I 2 batteries. The pMA@AC cathode exhibits a high capacity of 1.6 mAh cm −2 and an ultra‐long lifespan over 20 000 cycles, benefiting the stable pouch cell with 440 mAh and 183 Wh kg −1 after 100 cycles. In/ex situ characterizations coupled with theoretical calculations demonstrate that polymelamine (pMA) catalyzed efficient I − /I 2 conversion, suppressing polyiodide formation and avoiding consequent shuttling for high Coulombic efficiency and enhanced lifespan. The high catalytic activity of pMA is attributed to the delocalized π electron cloud on ─N═N─ sites, which connect to electron‐withdrawing triazine groups, with weaker physicochemical adsorption to I − /I 2 than traditional carbon‐based catalysts. It thus boosts the formation/desorption of resultant I 2 molecules at higher potential for enhanced cycling stability. More importantly, pMA@AC exhibits robust catalytic ability for four‐electron I − /I 0 /I + chemistry with 405 mAh g −1 and 10 000 cycles, further strengthening the potential application of such azo compounds for advanced Zn‐halogen batteries.