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

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^-2). 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^-1 at 1C under a high mass loading of ∼8.0 mg_iodine cm^-2, 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.