A P2-Na0.67Co0.5Mn0.5O2 cathode material with excellent rate capability and cycling stability for sodium ion batteries

Sodium ion batteries are considered as next-generation energy storage devices; however, stable cathode materials are highly desirable and challenging for sodium ion batteries. Herein, we report the preparation of a layered cathode material, P2-Na0.67Co0.5Mn0.5O2, with a hierarchical architecture, through a facile and simple sol-gel route. X-ray diffraction (XRD) and high resolution transmission electron microscopy elucidated a well-defined P2-type phase structure, and in situ XRD measurements provided further evidence about the structural stability during desodiation/sodiation. Benefiting from the structural stability, the cathode material delivered a high discharge capacity of 147 mA h g(-1) at 0.1C rate, and excellent cyclic stability with nearly 100% capacity retention over at least 100 cycles at 1C. More importantly, 88 mA h g(-1) was maintained when the electrode was cycled at a very high rate of 30C, and almost half of its capacity was retained over 2000 cycles, which outperforms all the reported P2-type cathode materials. With outstanding electrochemical performance and structural flexibility, the P2-Na0.67Co0.5Mn0.5O2 cathode material will promote the practical applications of sodium ion batteries.