Rational design of intergrowth P2/O3 biphasic layered structure with reversible anionic redox chemistry and structural evolution for Na-ions batteries

Authors：Zhang, Liuyun; Guan, Chaohong; Zheng, Jingqiang; Li, Huangxu; Li, Shihao; Li, Simin; Lai, Yanqing; Zhang, Zhian^*

Source：Science Bulletin, 2023, 68(2): 180-191.

DOI：10.1016/j.scib.2023.01.010

• Layered oxide cathodes
• Bi
• multi-phase
• Anionic redox
• Sodium -ion batteries
• Intergrowth structure

Layered oxides have attracted unprecedented attention for their outstanding performance in sodium-ion battery cathodes. Among them, the two typical candidates P2 and O3 type materials generally demon-strate large diversities in specific capacity and cycling endurance with their advantages. Thus, composite materials that contain both P2 and O3 have been widely designed and constructed. Nevertheless, the anionic/cationic ions' behavior and structural evolution in such complex structures remain unclear. In this study, a deep analysis of an advanced Na0.732Ni0.273Mg0.096Mn0.63O2 material that contains 78.39 wt% P2 phase and 21.61 wt% O3 phase is performed based on two typical cathodes P2 Na0.67Ni0.33Mn0.67O2 and O3 NaNi0.5Mn0.5O2 that have the same elemental constitution but different crys-tal structures. Structural analysis and density functional theory (DFT) calculations suggest that the com-posite is preferred to form a symbiotic structure at the atomic level, and the complex lattice texture of the biphase structure can block unfavorable ion and oxygen migration in the electrode process. Consequently, the biphase structure has significantly improved the electrochemical performance and kept preferable anionic oxygen redox reversibility. Furthermore, the hetero-epitaxy-like structure of the intergrowth of P2 and O3 structures share multi-phase boundaries, where the inconsistency in elec-trochemical behavior between P2 and O3 phases leads to an interlocking effect to prevent severe struc-tural collapse and relieves the lattice strain from Na+ de/intercalation. Hence, the symbiotic P2/O3 composite materials exhibited a preferable capacity and cyclability (-130 mAh g-1 at 0.1 C, 73.1% capac-ity retention after 200 cycles at 1 C), as well as reversible structural evolution. These findings confirmed the advantages of using the bi/multi-phase cathode for high-energy Na-ion batteries.

• Institution
  上海交通大学