• • Iodine cathodes offer a theoretical specific capacity of 211 mAh g−1 and a moderate redox potential of ~1.3 V, but suffer from poor conductivity and polyiodide shuttle, limiting cycle life and rate performance.
• • Physical confinement in porous carbons with high specific surface area (e.g., >1000 m2 g−1) effectively traps iodine species, but alone is insufficient to suppress shuttling; chemical adsorption via nitrogen doping enhances binding of I3− and I2, improving capacity retention.
• • Electrocatalytic hosts, particularly single-atom catalysts (e.g., Co, Zn) anchored on nitrogen-doped porous carbon, significantly accelerate iodine redox kinetics, enabling high-rate performance and long-term cycling stability (e.g., >10,000 cycles at high current densities).
• • Multi-electron iodine redox pathways (e.g., four-electron I−/I2/I+ and twelve-electron I−/I2/I+/IO3−) can theoretically boost energy density, but require stabilization of I+ via halogen coordination (e.g., Cl−, Br−) or other strategies to overcome high activation barriers.