Shielding Surface Oxygen via Cationic Charge Anchorage To Stabilize Reversible Anionic Redox in Lithium-Rich Layered Oxides

Abstract

Lattice oxygen (O2–) redox holds immense promise for maximizing the capacity of lithium-rich layered oxides, yet harvesting this potential is bottlenecked by the chemical instability of undercoordinated surface oxygen. Under high-voltage driving, the low symmetry and dangling bonds of these surface sites elevate the O 2p band center closer to the Fermi level, triggering premature electron extraction and irreversible gas evolution. Because these electron-rich surface oxygen species act as strong Lewis bases, quenching their excessive reactivity requires a localized charge-density countermeasure. Here, we introduce highly polarizable, large-radius cesium ions (Cs+) to construct a localized charge-shielding layer via specific cationic anchorage. Driven by ion–ion interactions, the highly diffuse electron clouds of Cs+ undergo charge polarization atop the dangling-bond oxygen sites, securely locking the surface electron density within the Mn–O framework. This polarization shield not only electrostatically arrests electron extraction from the lattice but also blocks solvent aggregation at the interface.