Constructing a Size-Controllable Spherical P2-Type Layered Oxides Cathode That Achieves Practicable Sodium-Ion Batteries

Abstract

P2-type layered metal oxides are regarded as promising cathode materials for sodium-ion batteries due to their high voltage platform and rapid Na + diffusion kinetics. However, limited capacity and unfavorable cycling stability resulting from inevitable phase transformation and detrimental structure collapse hinder their future application. Herein, based on P2-type Na 0.67 Ni 0.18 Mn 0.67 Cu 0.1 Zn 0.05 O 2, we synthesized a series of secondary spherical morphology cathodes with different radii derived from controlling precursors prepared by a coprecipitation method, which can be promoted to large-scale production. Consequently, the synthesized materials possessed a high tap density of 1.52 g cm –3 and a compacted density of 3.2 g cm –3 . The half cells exhibited a specific capacity of 111.8 mAh g –1 at a current density of 0.1 C as well as an 82.64% capacity retention with a high initial capacity of 85.80 mAh g –1 after 1000 cycles under a rate of 5 C. Notably, in situ X-ray diffraction revealed a reversible P2–OP4 phase transition and displayed a tiny volume change of 6.96% during the charge/discharge process, indicating an outstanding cycling stability of the modified cathode. Commendably, the cylindrical cell achieved a capacity of 4.7 Ah with almost no change during 1000 cycles at 2 C, suggesting excellent potential for future applications.