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

Abstract

Aqueous zinc–iodine batteries hold immense potential for sustainable energy storage applications, yet suffer from polyiodide shuttling and high-valent iodine instability. These challenges are further exacerbated at low temperatures due to incomplete conversion and sluggish redox kinetics, thereby 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 mA h 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 °C, the battery maintains 100.0% capacity retention over 495 continuous days (11 890 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.