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.