Bioinspired Molecular Screening of Zwitterionic Dipeptides for Stable Ah-Level Zinc-Iodine Batteries

Aqueous zinc-iodine (Zn─I₂) batteries are attractive for large-scale energy storage yet remain limited by two coupled failure mechanisms: unstable zinc interface at the anode and polyiodide shuttling at the cathode. To address both challenges with a single additive, we systematically screened 44 amino acids and dipeptides using molecular dipole moment and LUMO energy as key descriptors. L-Carnosine (LC) emerged as a unique candidate exhibiting both the highest dipole moment and a moderate LUMO energy across the screened library. Experimentally, LC's zwitterionic, multicenter charge distribution drives persistent multidentate adsorption at the zinc interface, suppressing HER, directing (101)-oriented crystallographic deposition through facet-selective passivation, and enabling formation of a vertically graded organic-inorganic hybrid solid electrolyte interphase. Concurrently, the electron-rich imidazole group rapidly quenches polyiodide intermediates through a rapid redox reaction. This synergistic regulation enables Zn||Zn symmetric cells to operate stably for 4980 h, Zn||Cu cells to achieve 99.76% average Coulombic efficiency (CE) over 1400 cycles, and Zn||I₂ full cells to sustain over 18 000 cycles with nearly 100% capacity retention. Furthermore, the practical viability is demonstrated in Ah-level pouch cells with 85% capacity retention after 500 cycles. This work establishes a unique molecular transformation strategy for stabilizing high-energy aqueous energy systems.