Aqueous rechargeable zinc-iodine batteries (ZIBs) are promising candidates for grid energy storage due to high energy density, low cost, and good safety. However, shuttling of highly soluble triiodide ions (I3-) lowers Coulombic efficiency, which hinders the commercialization. Herein, we demonstrate for the first time a double-layered cathode configuration with a conductive layer (CL) coupled with an adsorptive layer (AL) for ZIBs. This unique cathode structure enables the formation and reduction of adsorbed I3- ions at the CL/AL interface, successfully suppressing I3- ions shuttling. A prototypical ZIBs using carbon cloth as CL and carbon-cloth-loaded polypyrrole (PPy) as AL simultaneously achieves outstanding Coulombic efficiency (up to 95.6%) and voltage efficiency (up to 91.3%) in aqueous ZnI2 electrolyte even at high-rate intermittent charging/discharging, without the need of ion selective membranes. The findings of this work provide new insights to the design and fabrication of practical ZIBs and other batteries based on conversion reactions.

Prototypical study of double-layered cathodes for aqueous rechargeable static Zn-I2 batteries

ACS Fall 2021

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