Halting Oxygen Evolution to Achieve Long Cycle Life in Sodium Layered Cathodes

Oxygen redox chemistries at high voltage have materialized as a revolutionary paradigm for cathodes with high-energy density; however, they are plagued by the challenges of labile oxygen loss and rapid degradations upon cycling, even after concerted endeavors from the research community. Here we propose a multi-concentration stratagem propelled by entropy reinforcement to enhance the electronic structure disorder (ESD) at high desodiation states for impeding undesired oxygen mobility and ensuring controlled oxygen activity, elucidated by density functional theory calculations. The increased disorder strengthens the reversible electrochemistry of lattice oxygen redox, leading to effectively suppressed P-O structural evolution and highly stable localized TMO6 octahedral environments, as demonstrated by soft/hard X-ray absorption spectroscopy. Furthermore, we reveal that a high-entropy state induced by cationic disordering has capacity to perturb cationic redox boundaries, significantly restraining the formation of detrimental P3' phases. As a consequence, the high-voltage cycling stability has been greatly enhanced, up to 4.4 V versus Na+/Na, with an impressive 90.1% capacity retention at 1C over 100 cycles and 76.1% capacity retention at 2C over 300 cycles. The resilient oxygen redox, enabled through the control of ESD, broadens the horizons for entropy engineering and lays the foundation for advancements in high-energy, long-cycling, safe batteries.