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

A new O3-Na(0.78)Li(0.18)Ni(0.25)Mn(0.583)O(w) 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). Ni(2+)/Ni(4+) is suggested to be the main redox center. Further optimization could be realized by tuning the combination and the ratio of transition metals.