Boosting Iodine Redox Kinetics by Nickel-Cobalt Diatomic Electrocatalyst for Zinc-Iodine Batteries

Single-atom catalysts (SACs) offer an efficient solution of a well-defined structure-activity relationship for boosting iodine redox kinetics and suppressing the shuttle effect in zinc-iodine (Zn-I₂) batteries, but the further upgradation of their electrocatalytic activity is still constrained to date. Herein, atomically dispersed transition-metal electrocatalysts comprised of heteronuclear nickel-cobalt diatomic sites anchored on porous carbon nanosheets (Ni-Co-DA/PCNs) are proposed by a novel interlayer-confinement pyrolysis strategy. Thereinto, the NiCoAl-layered double hydroxides are employed as the 2D topological structure to induce the confined polycondensation of aromatic hydrocarbon precursors, and the transition-metal ions are simultaneously trapped in hierarchical carbon frameworks by the oxygen-containing species. The detailed experimental investigations combined with the in situ Raman spectroscopy reveal that the Ni-Co-DA/PCNs electrocatalyst with well-defined M-O₄ pair and high specific surface area is capable of facilitating the adsorption and fast conversion of polyiodides, thereby accelerating the redox kinetics of I₂/I^‒ and protecting zinc anode. Consequently, the assembled Zn-I₂ batteries with the Ni-Co-DA/PCNs/I₂ cathode exhibit a high discharge capacity of 216.7 mAh g^‒1 at 0.2 A g^‒1 with excellent rate capability and ultralong cycling lifespan over 9000 cycles with a capacity decay of only 0.0018% per cycle, which is far superior to those of Ni/Co SACs. This work provides a new insight into the design of dual-atom catalysts for Zn-halogens batteries.