Ta 5d‐Orbital‐Mediated Local Electronic‐Structure Regulation Enables Durable 4.7 V LiCoO 2 Cathodes

ABSTRACT Raising the cutoff voltage of LiCoO 2 (LCO) is an effective route to increase energy density, yet it inevitably aggravates lattice oxygen instability, interfacial parasitic reactions, and bulk structural degradation under deep delithiation. Herein, we propose a tantalum (Ta)‐enabled local spin regulation strategy to stabilize high‐voltage LCO. Owing to the spatially extended 5d orbitals and strong spin‐orbit coupling of Ta, short‐range Ta─O─Co coupling perturbs the local ligand field of neighboring Co sites, inducing 5d‐orbital‐mediated spin polarization and reconstructing the local Co─O electronic structure. This localized electronic regulation increases the calculated energetic separation between Co 3d and O 2p states and weakens their detrimental band overlap, thereby suppressing oxygen release, facilitating Li + diffusion, and mitigating both surface degradation and bulk phase transitions during cycling. As a result, Ta@LCO cathode exhibits markedly improved high‐voltage reversibility and durability, delivering 91.2% retention of its initial capacity after 600 cycles at 1 C and 80.9% capacity retention after 1000 cycles at 5C within 3.0–4.6 V. More importantly, Ta@LCO cathode can maintain even 71% after 550 cycles with an ultrahigh voltage of 4.7 V. This work highlights 5d‐element‐induced spin‐state engineering as an effective avenue for developing durable high‐voltage layered oxide cathodes.