High Capacity O3-Type Na[Li-0.05(Ni0.25Fe0.25Mn0.5)(0.95)]O-2 Cathode for Sodium Ion Batteries

Abstract

In this work we report Na[Li-0.05(Ni0.25Fe(0.25)Mn(0.5))(0.95)]O2 layered cathode materials that were synthesized via a coprecipitation method. The Na[Li-0.05(Ni(0.25)Fe0.25Mn(0.5))(0.95)]O-2 electrode exhibited an exceptionally high capacity (180.1 mA h g1 at 0.1 C-rate) as well as excellent capacity retentions (0.2 C-rate: 89.6%, 0.5 C-rate: 92.1%) and rate capabilities at various C-rates (0.1 C-rate: 180.1 mA h g1, 1 C-rate: 130.9 mA h g1, 5 C-rate: 96.2 mA h g1), which were achieved due to the Li supporting structural stabilization by introduction into the transition metal layer. By contrast, the electrode performance of the lithium-free Na[Ni0.25Fe0.25Mn0.5]O-2 cathode was inferior because of structural disintegration presumably resulting from Fe3+ migration from the transition metal layer to the Na layer during cycling. The long-term cycling using a full cell consisting of a Na[Li-0.05(Ni0(.25)Fe(0.25)Mn(0.5))(0.95)]O-2 cathode was coupled with a hard carbon anode which exhibited promising cycling data including a 76% capacity retention over 200 cycles.