Enhancing the Chemical Stability of Layered Oxides via P─O Bonds Coupling Lattice Oxygen Reactions.

Abstract

Oxygen reductive (OR) reactions at elevated voltages hold immense promise for advancing high-energy-density cathode development. Nevertheless, despite substantial research efforts, irreversible lattice oxygen desorption and accelerated structural degradation during cycling remain challenges. To address these issues, we propose a dual-pronged strategy: incorporating long-chain P─O bonds (P₂O₇ ^4-) to couple oxygen reactions while simultaneously constructing ordered-disordered nanodomains. Further studies indicate that under high-voltage conditions, the coupling between implanted P─O bonds and lattice oxygen manifests as a more reversible OR reaction and a reduction in oxygen escape. Simultaneously, these enhanced ordered-disordered nanodomains promote synchronous and uniform structural evolution, effectively suppressing P─O phase structural evolution (manifested as reduced lattice parameter deviation in P-type regions and rapid P3-OP2 biphasic reactions) while forming a highly stable local TMO₂ octahedral environment. Furthermore, density functional theory (DFT) analysis and soft X-ray absorption spectroscopy (XAS) confirmed that P─O bond incorporation significantly mitigated irreversible oxygen depletion and transition metal (TM) migration, thereby extending the chemical stability of layered oxides. As a result, the high-voltage cycle stability has been significantly enhanced, achieving a 30% improvement in capacity retention after 400 cycles at 1C (1C = 140 mAh g^-1). This work has opened up new avenues for enhancing the performance of sodium-ion battery cathodes.