A new O3-type layered oxide cathode with high energy/power density for rechargeable Na batteries

A new O3-Na0.78Li0.18Ni0.25Mn0.583Ow is prepared as the cathode material for Na-ion batteries, delivering exceptionally high energy density and superior rate performance. The single-slope voltage profile and ex situ synchrotron X-ray diffraction data demonstrate that no phase transformation happens through a wide range of sodium concentrations (up to 0.8 Na removed). Ni2+/Ni4+ is suggested to be the main redox center. Further optimization could be realized by tuning the combination and the ratio of transition metals.