A sustainable aqueous Zn-I₂ battery

Rechargeable metal-iodine batteries are an emerging attractive electrochemical energy storage technology that combines metallic anodes with halogen cathodes. Such batteries using aqueous electrolytes represent a viable solution for the safety and cost issues associated with organic electrolytes. A hybrid-electrolyte battery architecture has been adopted in a lithium-iodine battery using a solid ceramic membrane that protects the metallic anode from contacting the aqueous electrolyte. Here we demonstrate an eco-friendly, low-cost zinc-iodine battery with an aqueous electrolyte, wherein active I2 is confined in a nanoporous carbon cloth substrate. The electrochemical reaction is confined in the nanopores as a single conversion reaction, thus avoiding the production of I₃^- intermediates. The cathode architecture fully utilizes the active I₂, showing a capacity of 255 mAh·g^-1 and low capacity cycling fading. The battery provides an energy density of ~ 151 Wh·kg^-1 and exhibits an ultrastable cycle life of more than 1, 500 cycles.