Multifunctional Janus Separator Engineering for Modulating Zinc Oriented Aspectant Growth and Iodine Conversion Kinetics toward Advanced Zinc-Iodine Batteries

Zinc-iodine (Zn-I₂) batteries are deemed as promising next-generation energy storage devices in view of immanent security and high capacity. Nevertheless, their applications are deteriorated by unruly dendritic Zn growth, severe polyiodide diffusion, and sluggish iodine redox kinetics. Herein, MXene-mediated Janus separators with heterogeneous double-sided interfaces are designed to simultaneously manipulate Zn deposition and accelerate iodine adsorption-conversion kinetics. The anode side is composed of zincophilic Cu-modified hollow MXene spheres, which not only decreases Zn nucleation energy barrier but also suppresses Zn dendrite growth by homogenizing electric field distribution and inducing oriented aspectant dendrite-free Zn growth between the separator and anode. While the cathode side, consisting of iodophilic Co-modified hollow N-doped MXene spheres, inhibits the polyiodide shuttling and promotes iodine electrocatalytic conversion through Co-N-C sites. Such an ingenious engineering of Janus separators achieves a durable circulation over 2900 h for Zn||Zn symmetric cells and brings about an ultrahigh capacity of 274 mAh g⁻¹ for Zn-I₂ batteries as well as an ignorable decay (0.001% per circle) after 20 000 cycles. The concept of Janus separator design by integrating interfacial chemistry regulation and physical structure optimization in this work provides inspiration for constructing advanced energy storage devices with exceptional overall performance.