Improving the Performance of Layered Oxide Cathode Materials with Football-Like Hierarchical Structure for Na-Ion Batteries by Incorporating Mg 2+ into Vacancies in Na-Ion Layers.

The development of advanced cathode materials is still a great interest for sodium-ion batteries. The feasible commercialization of sodium-ion batteries relies on the design and exploitation of suitable electrode materials. This study offers a new insight into material design to exploit high-performance P2-type cathode materials for sodium-ion batteries. The incorporation of Mg2+ into intrinsic Na+ vacancies in Na-ion layers can lead to a high-performance P2-type cathode material for sodium-ion batteries. The materials prepared by the coprecipitation approach show a well-defined morphology of secondary football-like hierarchical structures. Neutron power diffraction and refinement results demonstrate that the incorporation of Mg2+ into intrinsic vacancies can enlarge the space for Na-ion diffusion, which can increase the d-spacing of the (0 0 2) peak and the size of slabs but reduce the chemical bond length to result in an enhanced rate capability and cycling stability. The incorporation of Mg2+ into available vacancies and a unique morphology make Na0.7 Mg0.05 Mn0.8 Ni0.1 Co0.1 O2 a promising cathode, which can be charged and discharged at an ultra-high current density of 2000 mA g-1 with an excellent specific capacity of 60 mAh g-1 . This work provides a new insight into the design of electrode materials for sodium-ion batteries.