Honeycomb Compound Na3Ni2BiO6 as Positive Electrode Material in Na Cells

Abstract

Honeycomb compound Na3Ni2BiO6 was synthesized and studied as positive electrode material in sodium cells for the first time. This material exhibits a reversible capacity of ∼80 mAh/g and an average voltage of ∼3.1 V, corresponding to the reversible removal of half of the sodium from the structure. The sodiation/desodiation mechanism was studied by in situ X-ray diffraction and involves multiple phase transitions. It was observed that the phase transitions are different for the first charge/discharge processes, possibly due to kinetic hindrance. The multiple phase transitions may lead to sluggish kinetics that are responsible for the poor rate capability.