Intensifying D-Orbitals Energy Level Splitting of Local Co Atoms in CoO Lattice for Accelerated Iodine Redox Kinetics.
basic_science · Level V
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- Record sourced from PubMed, PMID 40923473.
- Also identified by DOI 10.1002/adma.202513526.
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Abstract
Modulating the electronic structure of catalysts to maximize their power holds the key to address the challenges faced by zinc-iodine batteries (ZIBs), including the shuttle effect and slow redox kinetics at the iodine cathode. Herein, oxygen vacancies is innovatively introduced into CoO lattice to create high-spin-state Co active sites in nonstoichiometric CoO<sub>1₋x</sub> nanocrystals supported by carbon nanofibers (H-CoO<sub>1₋x</sub>/CNFs). This simple strategy intensifies crystal field splitting of Co 3d orbitals, optimizing the spin-orbital coupling between Co 3d orbitals and iodine species. The resulting enhanced availability of more unpaired electrons in non-degenerate e<sub>g</sub> orbitals facilitates faster electron donation/acceptance during iodine redox reactions, thus improved reaction kinetics. Therefore, the assembled ZIBs employing H-CoO<sub>1₋x</sub>/CNFs/I<sub>2</sub> cathode acquires a narrower overpotential gap (37 mV), higher initial capacity (203.0 mAh g<sup>‒1</sup>), and better cycling stability (96.0% capacity retention after 2200 cycles at 0.5 A g<sup>‒1</sup>) compared to the CoO/CNFs/I<sub>2</sub> cathode without experiencing defect engineering (109 mV/192.6 mAh g<sup>‒1</sup>/74.7% after 1000 cycles). This work opens new avenues for maximizing the potential power of cathode host catalysts, making immediate contributions to the advancement of aqueous halogen batteries.