Breaking 4.5 V‐Class Oxidation Limit of Sodium Layered Oxide Cathode by Anchoring Local Tripodal‐Ligand Structure

Abstract

Layered manganese‐rich oxides (LMROs) confront a dual degradation dilemma of fatal phase transition induced by weak electrostatic shielding effect and structural collapse triggered by oxygen escape under high voltages (>4.0 V). Herein, a local ligand anchoring strategy is proposed that constructing a non‐substituted BO3 tripodal support unit within the LRMOs framework, and the mechanism for synergistically stabilizing the lattice and interface to surpass the voltage threshold is comprehensively elucidated. The in‐plane BO3 unit shared adjacent oxygen coordination with the transition metal (TM) is anchored at tetrahedral interstitial sites above sodium vacancies, enhancing TM─O bonding and fundamentally inhibiting oxygen loss under high voltage via the charge redistribution induced by the electron‐deficient nature. Meanwhile, the rigid triangular configuration effectively disperses stress accumulation by disrupting the original long‐range ordered structure to neutralize lattice distortion during deep discharge, manifested as mitigated volume abrupt change and maintained structural integrity. Benefiting from the stabilized structure and B‐mediated subsurface, the modified cathode breaks 4.5 V oxidation limits and overcomes the voltage‐capacity trade‐off barrier (a high capacity of 189.8 mAh g−1 with sufficient energy density of 508 Wh kg−1). This work provides new insights into the rational design of breaking high‐oxidation limits of layered‐oxide cathodes for more practical sodium‐ion batteries.