Synthesis and properties of Na_(0.8)Ni_(0.4)Mn_(0.6)O_2 oxide used as cathode material for sodium ion batteries

摘要

A new P2-structured oxide Na_(0.8)Ni_(0.4)Mn_(0.6)O_2 was synthesized using a solid reaction method in which Na_2 CO_3, MnO_2 and NiO were used as starting materials.This oxide has a high amount of electrochemically active Ni and exhibits good electrochemical intercalation behavior of Na ions, including good rate capability and good cycle performance at both room temperature and elevated temperature. It displays two apparent voltage plateaus at about 3.6 and 3.3 V, and its discharge capacity reaches92 mAh·g^(-1) at 0.1 C in the voltage range of 2.0-4.0 V. At1.0 C, its discharge capacity reaches 85.3 mAh·g^(-1). After80 cycles at different current rates, the as-prepared sample exhibits good capacity retention. At elevated temperature of 55 ℃, the discharge capacity remains the same at low current rate of 0.1 C, but at high current rate of 1.0 C, the discharge capacity is a little lower than that at room temperature.