4f-5d orbital tag-team catalysis empowers high-loading zinc–iodine batteries

Conversion-type positive electrodes offer high theoretical energy density for next-generation energy storage, but their practical application is limited by severe shuttle effects and sluggish kinetics under high loadings. Achieving strong adsorption and fast redox kinetics is challenging, as the Sabatier principle implies that overly strong adsorption stabilizes intermediates and inhibits their conversion. Herein, we propose and validate an f-d orbital tag-team catalysis mechanism that overcomes this limitation within a model zinc | |iodine system. Leveraging a machine learning-guided descriptor framework, we identify cerium single-atom catalysts as an optimal catalytic center for iodine conversion, surpassing d-block analogues. Density functional theory calculations reveal a tag-team catalytic mechanism in which Ce 5 d orbitals strongly anchor iodine intermediates while near-Fermi-level Ce 4 f orbitals introduce antibonding interactions that exert tunable electronic repulsion on the I - I bond. This orbital tag-team catalysis mechanism enables simultaneous stabilization of polyiodide intermediates and facilitation of bond activation, achieving an iodine loading of 44.7 mg cm^-2 with an areal capacity of 10 mAh cm^-2, and a practical pouch cell capacity at a high mass loading of 115 mg cm^-2. This work bridges the orbital-level catalyst design with practical performance, offering a strategy for advancing high-loading conversion-type positive electrodes in battery systems.