Enhanced rate and cycling performance of O3-NaNi0.5Mn0.5O2 via unique dual-spacing modulation as sodium-ion cathode materials

Layered O3-type oxides have attracted significant interest as high-capacity cathode materials for sodium-ion batteries, owing to their ample sodium storage and competitive energy density. However, their practical implementation is hindered by irreversible phase transitions and sluggish Na + diffusion kinetics, leading to rapid capacity decay. Herein, we realize a unique dual-spacing modulation in O3-NaNi 0.5 Mn 0.5 O 2 cathodes via rational Cu substitution to effectively mitigate these intrinsic challenges. Comprehensive structural characterization reveals that this targeted modulation simultaneously expands the Na + layer spacing to facilitate ionic transport and contracts the transition metal slabs to enhance structural coherence. Consequently, the optimized NaNi 0.45 Mn 0.5 Cu 0.05 O 2 electrode delivers a high reversible capacity of 129.0 mA h g − 1 at 0.5 C, with exceptional cycling stability (83.3% capacity retention after 100 cycles) and outstanding rate capability (94.6 mA h g − 1 at 5 C). Furthermore, even within an extended voltage window (2.0–4.3 V), the material maintains a retention of 69.3% due to enhanced structural integrity. When paired with a commercial hard carbon anode, the resulting full cell demonstrates performance analogous to the half-cell configuration, underscoring its promising potential for large-scale commercialization. Graphical