Electrochimica Acta, Vol.113, 200-204, 2013
Electrochemical properties of P2-Na-2/3[Ni1/3Mn2/3]O-2 cathode material for sodium ion batteries when cycled in different voltage ranges
P2-type Na-2/3[Ni1/3Mn2/3]O-2 cathode material has been synthesized via spray drying method and a two step solid state process. Electrochemical behavior of the prepared material as cathode material for sodium ion battery was investigated in different charge-discharge voltage ranges. The results indicated that the cycling performance of the P2-Na-2/3[Ni1/3Mn2/3]O-2 cathode greatly depended on the voltage window. The material showed excellent reversibility between 2.0V and 4.0V with reversible capacity of 86 mAh g(-1) (0.1 C) and 77 mAh g(-1) (1 C). XRD analyses indicated that crystal structure of the P2-type Na-2/3[Ni1/3Mn2/3]O-2 could be well maintained after long term cycling in 2.0-4.0V. When the upper limiting voltage was increased to 4.5V, the crystal structure of P2-Na-2/3[Ni1/3Mn2/3]O-2 was irreversibly damaged due to over extraction of Na+ in 4.0-4.5V. On the other hand, when the cycling voltage range was between 1.6V and 3.8V, the discharge capacities increased to 135 mAh g(-1) (0.1 C) and 108 mAh g(-1) (1 C), respectively. However, the cycling stability in 1.6-3.8V was not as excellent as that in 2.0-4.0V. This maybe due to the lattice stress caused by the over insertion of Na+ in the structure at lower voltage. (C) 2013 Elsevier Ltd. All rights reserved.