Competitive solvent occupation chemistry enabling robust four-electron conversion for anti-freezing aqueous zinc-iodine batteries

Abstract

Aqueous zinc-iodine batteries hold immense promise for sustainable energy storage, yet suffer from polyiodide shuttling and high-valent iodine instability. Challenges undergo catastrophic amplification at low-temperatures due to incomplete conversion and retarded redox kinetics, undermining performance and longevity. Here, a competitive solvent-occupation strategy is proposed to enable highly reversible four-electron conversion in aqueous zinc-iodine batteries across a wide-temperature range. The entropic hydrogen-bond reconstruction coupled with tailored desolvation dynamics mediates the thermodynamic stability and electrochemical redox depth of I+ species. This approach achieves a near-theoretical conversion depth of 97.2% and a high reversible capacity of 410.2 mAh g-1, where the high plateau at 1.68 V triggered by the I0/I+ couple contributes 51.7% of the total capacity at 1.0 A g-1. Even at -20 ℃, the battery maintains 100.0% capacity retention over 495 continuous days (11890 hours), while preserving stable high-voltage output at 1.55 V. Synergistic spectroscopy-modeling decouples the robust cryogenic mass-electron transfer pathways underlying the near-stoichiometric iodine conversion chemistry. This work pioneers a fundamental framework for designing energetic and temperature-adaptive aqueous zinc-iodine batteries.