Polyethylene oxide binder suppressing polyiodide shuttling via charge-transfer complexation for high-mass-loading aqueous zinc iodine batteries.

Aqueous zinc iodine batteries (AZIBs) offer significant advantages in safety and cost, making them promising candidates for large-scale energy storage. However, the polyiodide shuttle effect impedes their commercialization process, especially when facing high areal capacity conditions (>3 mAh cm). Designing advanced multifunctional binders emerges as an urgent and efficient tactic to address polyiodide shuttling and sustain the structural integrity and ionic conduction of thick electrodes simultaneously. This work reports a commercially available water-soluble binder with high ionic conductivity and moderate viscosity, polyethylene oxide with a molecular weight of 300,000 (PEO-30), which can chemically adsorb and immobilize iodine species by forming charge-transfer complexes with high electrical conductivity, thereby suppressing the polyiodide shuttling and enhancing reaction kinetics. As a result, the PEO-30 binder-based AZIBs achieve a specific capacity of 208.6 mAh g at 1C under a high mass loading of ∼8.0 mg cm, and maintain an average coulombic efficiency of 99.86% over 3000 cycles. An ultra-stable cycling life is obtained with the capacity retention of 93.81% after 33,000 cycles at 20 C, demonstrating the effectiveness of PEO in immobilizing iodine species and facilitating rate performance of the thick electrodes. The non-toxic and non-irritating nature of the PEO binder provides a new pathway for the practical application of green, low-cost, and practical AZIBs.