Shuttle-free zinc–iodine batteries enabled by a cobalt single atom anchored on N-doped porous carbon host with ultra-high specific surface area

Abstract

Aqueous zinc‑iodine batteries are favorable solutions for grid-level energy storage owing to their cost-effective components and intrinsic safety. Nevertheless, the sluggish conversion kinetics and polyiodide shuttle effect have significantly hindered their practical applications. Herein, a Co single atom anchored on N-doped porous carbon nanosheets (Co-SAs@NPC) was produced through an efficient molten-salt engaged pyrolysis process and further utilized as the iodine host for aqueous zinc-iodine batteries. The large specific surface area (1741 m2 g−1) combined with abundant heteroatom-containing functional groups can afford a tight physical and chemical confinement towards iodine species. Meanwhile, the presence of Co single atoms exhibits high electrocatalytic activity towards I2 reduction reactions. According to the experimental results and DFT theoretical calculations, the resulting Co-SAs@NPC can simultaneously offer generous electrochemical active sites and electrocatalytic activity, which displays a high adsorption ability towards iodide species and boost the reversible redox reactions between iodine and iodides. Consequently, the as-assembled zinc-iodine batteries with Co-SAs@NPC/I2 cathodes can deliver a high specific capacity (295 mA h g−1 at 0.3 A g−1), good rate performance (199 mAh g−1 at 20 A g−1), and long cyclic stability over 10,000 cycles. Additionally, the absence of polyiodide shuttle was analyzed by a series of ex-situ spectrum analyses.