Positive Phase Transformation Realizing 99.8% Initial Coulombic Efficiency Within Modified P2‐Typed Layer‐Structured Oxide

Abstract Irreversible P2‐O2 phase transformation at high‐voltage within P2‐type layered oxides results in the structural degradation, inferior diffusion kinetics and unsatisfied reversibility. Oxygen layered reconfiguration strategy toward P2‐typed Na 0.75 Ni 0.3 Mn 0.5 Cu 0.1 Ti 0.05 Mo 0.05 O 2 is thus utilized to realize a twin structure to achieve high energy density and high reversibility with long cycling lifespan. Under high‐voltage conditions, the introduction of twin boundaries with symmetrical ‘ABAB’ oxygen atom arrangement can modulate the local bonding environment by shortening TM─O bond lengths and enhancing the orbital hybridization, which collectively reinforce Mn─O covalency and stabilize lattice oxygen. The simultaneously reduced oxygen anion charge density and expanded interlayer spacing can effectively alleviate interlayer electrostatic repulsion, thereby suppressing the irreversible P to O‐type layers transition. Meanwhile, the overlap of the valence and conduction bands at the Fermi level induced by the twin structure leads to an interfacial semi‐metallic behavior along the ion transport pathways and consequently enhances the bulk electronic conductivity. The modified material exhibits a high up to 99.8% initial coulombic efficiency, with capacity retentions of 84.47% and 84.2% after 314 cycles at 5 C and after 624 cycles at 10 C, respectively. This work deepens the understanding into the mechanism of oxygen arrangement and twin structure.