Integrated confinement-chemisorption-catalysis cathode for highly stable zinc-iodine batteries

Zinc-iodine (Zn-I 2 ) batteries are deemed as potential candidate of energy storage system for the merits of high safety, cost-effectiveness, high capacity, and environmental compatibility. Unfortunately, the practical implementation of Zn-I 2 batteries is still hindered by the sluggish iodine redox kinetics and the shuttle effect of soluble polyiodides, which induce rapid capacity decay and electrode interface passivation. This work proposes platinum/carbon (Pt/C) and iridium/carbon (Ir/C) composite as conductive catalytic iodine hosts, which realizes the physical confinement for active iodine through the intrinsic porous structure. The introduction of active Pt/Ir sites effectively anchors the polyiodides through chemical adsorption capability, and inhibits shuttle effect and Zn metal corrosion. In addition, the superior electrical conductivity and catalytic activity of Pt/C and Ir/C carriers also contribute to reduce the reaction energy barriers, significantly promoting the electrochemical performance and conversion reaction kinetics. As expected, the assembled Zn//Pt/C@I 2 and Zn//Ir/C@I 2 batteries achieve impressive reversible capacity of 132.2 and 108 mAh g −1 after 2 000 cycles at 200 ​mA ​g −1 , respectively, and their capacity retention rate after 25 000 cycles at 1 000 ​mA ​g −1 are as high as 88.1 ​% and 85.9 ​%. This study will guide the carrier design of iodine cathode to drive the application of high-performance Zn-I 2 batteries. Owing to the abundant active sites and strong adsorption capability, the optimized Pt/C catalytic carrier achieves the dual inhibition effect of polyiodide migration and zinc metal corrosion, synergistically promoting the durable cyclic stability of zinc-iodine batteries.