Activating iodine redox by enabling single-atom coordination to dormant nitrogen sites to realize durable zinc–iodine batteries

Aqueous rechargeable static zinc–iodine (Zn–I₂) batteries are regarded as competitive candidates for next-generation energy storage devices owing to their safety and high energy density. However, their inherent limitations such as the shuttle effect, sluggish electrochemical kinetics, and the poor electrical conductivity of iodine have been challenging to mitigate when using methods that confer polarity to the surface of the carbon host through nitrogen doping. Moreover, the considerable prevalence of inactive pyridinic N sites significantly impedes the establishment of approaches to overcome issues associated with redox kinetics and iodine utilization. Herein, single Ni atoms were incorporated into an electrochemically inactive N-doped carbon matrix by carbonizing a zeolitic imidazolate framework and then thermally activating the Ni ions adsorbed onto the carbonized product. The single Ni atoms modulated the electronic structure of the surrounding N-doped carbon matrix, thereby improving its ability to adsorb polyiodides and exhibit bifunctional catalytic activity for iodine reduction and oxidation reactions. Consequently, the assembled Zn–I₂ battery delivered an outstanding rate performance (193 mA h g^̶1 at a current density of 6 A g^̶1) and ultralong cyclability (10 000 cycles at a current density of 4 A g^̶1). Overall, this study illuminates the merits of using single-atom catalysts to revitalize inactive N pyridinic sites, thereby providing a promising direction for further advancement of Zn–I₂ batteries.