P2/O3 biphase integration promoting the enhancement of structural stability for sodium layered oxide cathode.

[Display omitted] • A series Na x TMO 2 with different P2/O3 ratio were synthesized by tuning Na contents. • Decreased Jahn-Teller Mn3+ in Na storage process with the increase of P2 phase ratio. • P2/O3 intergrowth structure mitigates O3 phase transition to poor Na O1 phase. • Alleviated volumetric change and improved Na+ diffusion rate benefit the performance. O3-type sodium layered oxides have garnered significant attention as highly promising candidates for sodium ion batteries due to their high theoretical capacity. However, they often encounter challenges associated with complex and irreversible phase transitions and sluggish kinetics. To overcome these issues, herein we integrate the O3-type phase with the P2-type phase and systematically investigate the influence of different ratios of P2 phase in O3-type Na x Li 0.05 Mn 0.55 Ni 0.3 Cu 0.075 Mg 0.025 O 2 pentanary layered oxides on the electrochemical performance by tuning the sodium contents. The LMC 3 -P2/O3-32 with optimized P2 phase ratio of 32.3 % exhibits a high reversible capacity of 157.0 mAh g−1 at a rate of 0.2C and excellent capacity retention rate of 63.5 % after 1000 cycles at 10C. The LCM 3 -P2/O3-32 also demonstrates good cycle life and rate capability in full cells when coupled with a hard carbon anode. In situ X-ray diffraction analyses confirm that the detrimental phase transformations to Na-poor O1 phase and the irreversible phase transitions occurred in the pure O3 cathode can be effectively suppressed in the P2/O3 biphasic cathode. The less Jahn-Teller active ions, enhanced phase transition reversibility and improved diffusion kinetics of Na+ ions are responsible for the improved cyclability and rate capability in the P2/O3 nanoscale intergrowth cathode. Our work shed light on the leverage of P2 and O3 phases through phase integration in layered oxides cathodes, which can serve as a guideline for the further development of high-performance cathode materials for advanced sodium ion batteries. [ABSTRACT FROM AUTHOR]