Interfacial Engineering of Iodine‐Polymer‐Carbon Hybrid Cathodes for High‐Energy Zn//I ₂ Microbatteries

ABSTRACT

Miniaturized energy‐storage devices with high energy density, fast charge‐storage kinetics, and long‐term durability are essential for next‐generation on‐chip electronics. Among various candidates, zinc‐iodine (Zn//I ₂ ) microbatteries (MBs) are attractive owing to their intrinsic safety, low cost, and rapid iodine redox chemistry. Herein, a printed coplanar Zn//I ₂ MB is developed using a cathode‐confined iodine strategy, in which redox‐active iodine is immobilized within a rationally engineered polyaniline (PANI) and activated‐carbon (AC) (I ₂ @AC‐PANI) composite cathode framework. The synergistic AC‐PANI architecture enhances iodine utilization, charge‐transfer kinetics, and electrochemical reversibility, resulting in improved capacity, rate capability, and cycling stability. Through a combination of ex situ spectroscopic analyses, electrochemical measurements, self‐discharge studies, and density functional theory (DFT) calculations, stronger interactions between iodine species and the AC‐PANI framework are identified, together with enhanced charge‐transfer characteristics compared with AC alone. As a result, the coplanar Zn//I ₂ microbattery delivers an areal energy of 36.35 µWh cm ⁻² at an areal power of 50 µW cm ⁻² and retains 86.4% of its initial capacity after 2000 cycles. This work demonstrates that cathode‐confined halogen chemistry combined with AC‐PANI engineering provides an effective strategy for developing high‐performance coplanar microbatteries and offers a promising route toward safe, integrable, and durable microscale energy‐storage systems.