Quenching‐Induced Structural and Electronic Modulations in Layered Fe–Mn–Ni Oxide Cathode for Enhanced Sodium Storage

Layered oxide NaFe_0.33Mn_0.33Ni_0.33O₂ (FMN) has emerged as a promising cathode material for sodium-ion batteries (SIBs) due to its high theoretical capacity and cost-effectiveness. However, its practical application is hindered by unsatisfactory reversible capacity and structural degradation during cycling. In this work, a precisely controlled quenching approach is demonstrated that substantially enhances the electrochemical performance of FMN. Systematic investigation reveals that FMN subjected to rapid quenching at 65°C·min^-1 exhibits remarkable improvements, delivering an initial discharge capacity of 141 mAh·g^-1 and maintaining 73.3% capacity retention after 100 cycles, outperforming the naturally cooled sample. The enhanced performance is attributed to the quenching-induced oxygen vacancies promoting pseudocapacitive sodium storage, the optimized interlayer sodium content facilitating ion transport, and the stabilized transition metal valence states suppressing Jahn-Teller distortions. These findings provide fundamental insights into structure-property relationships in quenched cathode materials and establish a facile yet effective strategy for developing high-performance SIB electrodes.