A Practical High-Energy Cathode for Sodium-Ion Batteries Based on Uniform P2-Na 0.7 CoO 2 Microspheres.

Layered metal oxides have attracted increasing attention as cathode materials for sodium-ion batteries (SIBs). However, the application of such cathode materials is still hindered by their poor rate capability and cycling stability. Here, a facile self-templated strategy is developed to synthesize uniform P2-Na _0.7 CoO ₂ microspheres. Due to the unique microsphere structure, the contact area of the active material with electrolyte is minimized. As expected, the P2-Na _0.7 CoO ₂ microspheres exhibit enhanced electrochemical performance for sodium storage in terms of high reversible capacity (125 mAh g ^-1 at 5 mA g ^-1 ), superior rate capability and long cycle life (86 % capacity retention over 300 cycles). Importantly, the synthesis method can be easily extended to synthesize other layered metal oxide (P2-Na _0.7 MnO ₂ and O3-NaFeO ₂ ) microspheres.
(© 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.)