"Proton-Iodine" Regulation of Protonated Polyaniline Catalyst for High-Performance Electrolytic Zn-I₂ Batteries

Low-cost and high-safety aqueous Zn-I₂ batteries attract extensive attention for large-scale energy storage systems. However, polyiodide shuttling and sluggish iodine conversion reactions lead to inferior rate capability and severe capacity decay. Herein, a three-dimensional polyaniline is wrapped by carboxyl-carbon nanotubes (denoted as C-PANI) which is designed as a catalytic cathode to effectively boost iodine conversion with suppressed polyiodide shuttling, thereby improving Zn-I₂ batteries. Specifically, carboxyl-carbon nanotubes serve as a proton reservoir for more protonated -NH⁺ = sites in PANI chains, achieving a direct I⁰/I^- reaction for suppressed polyiodide generation and Zn corrosion. Attributing to this "proton-iodine" regulation, catalytic protonated C-PANI strongly fixes electrolytic iodine species and stores proton ions simultaneously through reversible -N = /-NH⁺- reaction. Therefore, the electrolytic Zn-I₂ battery with C-PANI cathode exhibits an impressive capacity of 420 mAh g^-1 and ultra-long lifespan over 40,000 cycles. Additionally, a 60 mAh pouch cell was assembled with excellent cycling stability after 100 cycles, providing new insights into exploring effective organocatalysts for superb Zn-halogen batteries.