Unlocking Air Stability in Defect-Free Na-Ion Layered Oxide Cathodes via Ultrafast Synthesis

The industrialization of O3-type cathodes for sodium-ion batteries (SIBs) is hindered by a critical vulnerability─severe air sensitivity, which causes irreversible structural degradation and performance decay upon exposure. Herein, we employ a high-temperature shock (HTS) synthesis process (>800 °C s^–1) governed by kinetic control. This ultrafast method suppresses the formation of impurities (like Na/Ni anti-sites and NiO phases), yielding a nearly defect-free lamellar framework. The resulting material exhibits intrinsic air stability stemming from its lattice integrity. This inherent stability prevents corrosion without extrinsic modifications, demonstrated by its retention of electrochemical performance even after direct water immersion. Consequently, this enables low-cost, environmentally benign aqueous electrode processing. The material retains approximately 70% of its capacity after 1500 cycles at a 2C rate, highlighting the HTS strategy as a broadly applicable pathway for the scalable manufacturing of air-stable cathodes.