High Performance Na0.5[Ni0.23Fe0.13Mn0.63]O2 Cathode for Sodium-Ion Batteries

Sodium batteries, as well as lithium batteries, were widely studied from the late 1970s and throughout the 1980s.[1] However, interest in sodium batteries rapidly vanished, owing to the superior properties of the lithium technology. But, the large diffusion of lithium batteries in the electronic consumer market contributed to a rapid rise in the price of lithium. Owing to the large availability of sodium and its low cost, ambient temperature Na-based batteries have the potential to meet large-scale grid-energy-storage requirements.[2]. Sodium has an ionic radius larger than lithium (1.06 Å vs 0.76 Å, respectively), preferring 6-fold coordination in octahedral or prismatic sites. This results in the confinement of the Na-based cathode structures into two big classes, i.e. poly-anionic networks[3] and layered compounds. The synthesis of a new layered cathode material, Na 0.5[Ni0.23Fe0.13Mn0.63]O2, and its characterization in terms of crystalline structure and electrochemical performance in a sodium cell, is reported. X-ray diffraction studies and high resolution SEM images reveal a welldefined P2-type layered structure, while the electrochemical tests evidence excellent characteristics in terms of high capacity, extending up to 200 mAh g-1, and cycle life, up to 70 cycles. This performance, in addition to the low cost and environmental compatibility of its component, poses Na 0.5[Ni0.23Fe0.13Mn0.63]O2among the best promising materials for the next generation of sodium ion batteries.