Layered Na[Ni1/3Fe1/3Mn1/3]O2 cathodes for Na-ion battery application

Na-ion batteries were tested with layered Na(Ni1/3Fe1/3Mn1/3)O2 cathodes and carbon anodes in a sodium-salt containing organic ester carbonate electrolyte. Layered single phase Na(Ni1/3Fe1/3Mn1/3)O2 was synthesized from solid-state reaction using a (Ni1/3Fe1/3Mn1/3)C2O4 oxalate precursor and Na2CO3 fired at 850 °C with slow-cooling. The Na-ion NayC/Na1 − y(Ni1/3Fe1/3Mn1/3)O2 cell had an average voltage of ~ 2.75 V, modest capacity of 100 mA h g− 1 for 150 cycles (1.5–4.0 V), and a capacity of 94 mA h g− 1 at a 1 °C rate. X-ray diffraction (XRD) data of extracted cycled electrodes were used to characterize material stability and phases formed upon cycling. It was found that Na1 − y(Ni1/3Fe1/3Mn1/3)O2 (0 ≤ y ≤ 0.46) maintains a layered structure with good crystallinity over 150 cycles. These results bode well for the development and optimization of rechargeable Na-ion batteries.